XENOBIOTICS
ACTING ON THE NERVOUS SYSTEM
Table of contents :
Types of
action
-
inhibition of neurotransmitter synthesis => depletion of neurotransmitter
-
metabolic transformation by same pathway as precursor of transmitter =>
displacement of the true transmitter by false transmitters
-
blockade of reuptake system at nerve terminal membrane => accumulation
of neurotransmitter at receptors and depletion of neurotransmitter
-
blockade of transport system of storage granule (vesicle) membrane => destruction
of neutrotrasmitter by cytoplasmic enzymes and depletion from nerve terminals
-
promotion of neuroexocytosis or displacement of transmitter from axonal
terminal => initial mimetic action followed by depletion
-
prevention of release of transmitter
-
mimicry of transmitter at postsynaptic receptor
-
blockade of endogenous transmitter at postsynaptic receptor
-
mimicry of transmitter at presynaptic receptor
-
blockade of endogenous transmitter at presynaptic receptor
-
inhibition of enzymatic breakdown of transmitter
PNS-directed
-
local anesthetics
induce loss of pain without loss of consciousness
-
voltage-gated Na+ channel
blockers : effectiveness ~ myelinization (drugs are lipophilic) ~ number
of channels in the open configuration (drugs enter channels in the protonated
form only and block them in the open configuration) ~ discharge rate ~
1 / Øneuron. Administration routes : topical, infiltrations,
regional IV injection, troncular (near nerves), spinal, epidural. Co-administer
a vasoconstrictor (e.g. epinephrine
)
to slow down clearance and avoid side effects from systemic spread.
Web resources : The
Virtual Library - Anesthesiology
-
phentolamine mesylate / NV-101 (source : Novalar
Pharmaceuticals, Inc.) : a vasodilator which acts a local dental anesthetic
reversal agent
-
anti-muscle
hyperactivity
-
s.c. / i.m. BoNT/A
(Botox®, originally Oculinum®; source : Allergan
Inc. of Irvine, Calif) is used in therapy of ...
Each vial of Botox contains 100 units of Clostridium botulinum neurotoxin
A complex that is vacuum-dried to be reconstituted before use.
The purpose of the therapies is to actually produce "local" botulism
of the musculature injected. If the cases of "systemic" botulism are due
to Botox
injections, it may be that the material was incorrectly diluted, too
large a volume of correctly diluted toxin was given, or a manufacturing
error occurred. If the latter occurred, more cases may be found. Therapy
must be continual since the effect of the toxin usually lasts for no more
than 3 to 6 months. Side effects are rare. A Florida woman died in
2003 after suffering an allergic reaction to Botox. But the company that
makes the drug stresses its safety record -- saying just 7 people had serious
side effects in the 1990s.
-
BoNT/B
(Myobloc® or Neurobloc®) was more recently
licensed by the FDA for cervical dystonia.
-
peripherally
active antiemetics (see also centrally
active antiemetics)
-
antivertiginous
drugs
-
cerebral CCB flunarizine
is effective in the treatment of vestibular disorders. Side
effects : somnolence, weight gain, and, in rare cases, extrapyramidal
symptoms and depression. This putative antivertiginous property is really
due to the anticalcic action of the drug and not to a more classical antagonistic
effect on H1 receptors
-
vasodilators
-
nicotinic acid

-
b-pyridylcarbinol
-
betahistine dihydrochloride (Serc®, Betaserc®,
Vasomotal®, Vertiserc®, Vertin®,
Urutal®, Agiserc®) is an orally effective
histamine-like drug. SERC® treats the underlying cause of vertigo by
normalizing the flow of impulses and improving blood flow in the inner
ear in the treatment of Ménière's disease and symptomatic
treatment of vestibular vertigo
-
nicotinyl alcohol (Roniacol®)
-
nylidrin (Arlidin®, Arlidin Forte®,
PMS Nylidrin®)
CNS-directed
-
general anesthetics
(intravenous or inhalatory) induce loss of sensation and consciousness
Suppression of nerve cell activity, required to form connections and thrive
in a baby's growing brain, leads to neuronal apoptosis.
-
full-face mask : a device used in anesthesia to confine the gas
to be delivered through the mask into the respiratory tract through the
nose or mouth.
-
needle-through-needle technique : a technique of anesthetic administration
in which a narrow spinal needle is advanced through the lumen of a larger-gauge
needle such as a Tuohy needle and past its tip to puncture the dura so
that spinal and epidural anesthesia can be administered at the same time.
-
central analgesics
(vs. nociceptive pain
)
-
m
opioid receptors
agonists :
-
systemic analgesic therapy
(SAT)
-
oral
-
oral transmucosal
-
parenteral
-
patient-controlled analgesia (PCA)
-
computer-assisted continuous infusion (CACI)
-
peripheral
-
rectal
-
nebulizer
-
transdermal
-
iontophoretic
-
intraspinal (epidural or intrathecal / "spinal") infusion
By combining m
opioid receptors agonists with NMDA-R
antagonists, tolerance is impaired and analgesia is enhanced
without an increase in the dose of opioid.
1 mg i.m. of morphine equals 3 mg p.o.
Acute toxicity (resulting from clinical
overdosage, accidental overdosage in addicts, or attempts at suicide) :
miosis (pinpoint pupils; mydriasis when asphyxia intervenes), nausea
and vomiting
due to CTZ stimulation, pulmonary edema, muscular rigidity (in the chest
wall => respiratory failure), catalepsy, circling, stereotypical behaviour,
decreased propulsive GI tract motility, increased pressure in the biliary
tract, pseudoimmunologic urticaria and asthma => anaphylactoid reactions,
dizziness, mental clouding, dysphoria, urinary retention, orthostatic hypotension,
respiratory depression (reduction in responsiveness of the brainstem respiratory
centers to PCO2 => apnea => respiratory arrest => cyanosis
=> death (greater risk if combined with general anesthetics, tranquilizers,
alohol, or sedative-hypnotics)
Chronic toxicity : GERD, constipation, immunosuppression
Treatment for chronic abuse :
-
maintenance programs to treat opioid withdrawal syndrome
-
stabilization with long-acting m
opioid receptor
agonists => not experience the ups and downs they experienced while
on heroin, drug craving diminishes and may disappear, neuroendocrine rhythms
eventually are restored.
-
methadone
: administered PO de visu, half-life = 15 hours, respiratory depression,
no theratogenic effect => used in addicted pregnants and newborns. It doesn't
cause mood instability, dysphoria, and craving. 80 mg for each g of heroin
assumed / die. Ethanol
,
diphenylidantoine
,
phenobarbital
,
carbamazepine
,
tetracyclines
,
and rifampicin
up-regulate methadone-catabolyzing cytochromes, while erythromycin
,
cimetidine
,
and ketoconazole
down-regulate their expression.
-
L-a-acetylmethadol
(LAAM) / levomethadyl acetate
: longer half-life (= 71-143 hours) => 60-140 mg every 2 days or 130+130+180
mg in a week. Theratogenic. Side effects :
fatigue, insomnia, cough, irritability, constipation, secondary
systemic arterial hypertension
,
bradycardia, hepatitis, exanthema, diplopia, sexual impotence.
-
nor-LAAM

-
dinor-LAAM

-
buprenorphine
: neither respiratory depression nor euphoria
-
inhibitors of noradrenergic neurotransmission from the locus ceruleus
(to replace loss of opioid suppression of the locus ceruleus systemm during
the abstinence syndrome) alleviate many of the symptoms of opioid withdrawal,
-
a2A
agonists
(clonidine) cause arterial hypotension as a side effect
-
I1 agonists
(lofexidine) don't cause arterial hypotension
-
activation of the endogenous opioid system with acupuncture
and several methods of CNS activation utilizing transcutaneous electrical
stimulation.
-
detoxification
-
gradually decreasing doses of m
opioid receptor
agonists to prevent withdrawal symptoms : -5 mg / days for 3 days (from
100 to 20 mg / day) => - 2 mg / day till the end (usually therapy lasts
for > 1 year). weekly control of opiate catabolytes in urine. If no catabolytes
are found for 3 weeks, domiciliary therapy can be evaluated for Sundays
=> week-ends => no longer than a week. Adjuvant therapy :
-
rapid opiate detoxification (ROD)
-
Waismann
Methodsm of Accelerated
Neuro-Regulation - formerly known as rapid detox : patients have a greater
than 64% chance of maintaining an opiate-free life based on 1-year research.
-
ultra-rapid opiate detoxification
(UROD) lasts 24 hours and consists of ...
-
12 hours : guanfacine
(to decrease blood pressure and heart rate prior, during and shortly after
detoxification)
-
3 hours :
-
naltrexone
(p.o., to precipitate withdrawal)
-
drugs to prevent peripheral side effects
from opiate antagonists :
-
general anaesthetic (midazolam
,
IV for 4 hours) : the patient is unconscious and thus not experiencing
withdrawal discomfort.
-
naloxone
(i.v., to test detoxification states about 4h after sleep induction),
-
at awakening : guanfacine
(continued administration in decreasing doses when patient begins to wake
up from sedation)
-
day after : naltrexone
(p.o.) (for 3 months). A depot formulation of naltrexone which provides
30 days of medication after a single injection is in clinical trials.
It removes physical
dependence
but not psychological
dependence
.
-
CB1
agonists
-
CB2
agonists are promising candidates for the treatment of
pain. CB2 receptor activation inhibits acute,
inflammatory, and neuropathic pain responses but does not cause CNS effects,
consistent with the lack of CB2 receptors
in the normal CNS. Activation stimulates release from keratinocytes of
the endogenous opioid b-endorphin,
which then acts at opioid receptors on primary afferent neurons to inhibit
nociceptionref.
-
NK1
antagonists works in animals but not in humans
-
RET
agonists
-
adenylate cyclase
inhibitors block coupling of NMDA-R
to cAMP
-
GABAB agonists
or GABA transaminase
inhibitors in rostral agranular insular cortex (RAIC)ref
(both the anterior cingulate cortex and insular cortex receive pain messages
and are thought to process motor and emotional responses to pain)
-
anti-headache

-
anti-migraine

-
centrally
active antitussive agents (see also peripherally
active antitussive agents)
-
opiate agonists
-
H1
antagonist
-
carbetapentane (Histatuss Pediatric®
in combination with chlorpheniramine, ephedrine, and phenylephrine)
-
caramiphen (Parpanit®, Taoryl®)
-
chlophedianol (Carafen Cough Syrup®;
Carafen Cough Tablets®, Parpanit®)
-
glaucine (Glauvent®)
-
pholcodine / 3-O-(2-morpholinoethyl)morphine
-
benzonatate (Tessalon®)
-
centrally active
antiemetics (see also peripherally
active antiemetics) (vs. nausea
and vomiting
)
-
anorexiants / appetite-suppressants
/ anorectic drugs (vs. obesity
)
-
anti-pediatric
anorexia
-
anti-male
and female sexual dysfunctions
-
MC1R
agonists (nasally administered peptides)
-
anti-CNS
neurodegenerative disorders

-
anti-Parkinson's
disease (PD)

-
direct and indirect dopaminergic agonists
-
dopamine
doesn't cross the blood-brain
barrier (BBB)
and is used as a peripheral vasoconstrictor
-
dopamine
precursors
-
levodopa / L-3,4-dihydroxyphenylalanine
(L-DOPA®, Larodopa®, Dopar®;
Sinemet® in combination with carbidopa
)
has t1/2 = 100' (4-5 doses a day).
Side effects : in early PD, the duration of
the beneficial effects of levodopa may exceed the plasma lifetime of the
drug, suggesting that the nigrostriatal dopamione system retains some capacity
to store and release dopamine. A principal limitation of the long-term
use (3 years or so) of levodopa is that, with time, this apparent "buffering"
capacity is lost, and the patient's motor state may fluctuate dramatically
with each dose of levodopa.
-
wearing off phenomenon : each dose of levodopa effectively improves
mobility for a period of time, perhaps 1 to 2 hours, but rigidity and akinesia
rapidly return at the end of the dosing interval. Increasing the dose and
frequency of administration can improve this situation, but this often
is limited by development of dyskinesias, observed most often when the
plasma levodopa concentration is high, although, in some individuals, dyskinesias
or dystonia may be triggered when the level is rising or falling. These
movements can be uncomfortable and disabling as the rigidity and akinesia
of PD. In the later stages of PD, patients may fluctuate rapidly between
being "off", having no beneficial effects from their medications, and being
"on" but with disabling dyskinesias, a situation called the on-off phenomenon
-
psychoses
,
treated with atypical antipsychotics
(conventional antipsychotics worsen parkinsonism)
Contraindications :
Associations with :
-
peripherally acting DOPA decarboxylase
inhibitors (benserazide and carbiDOPA) : othwerwise peripherally produced
dopamine would cross the blood-brain barrier on ly by 1% and would affect
peripheral receptors causing nausea
and vomiting
-
peripherally acting COMT
inhibitors
-
centrally acting MAO-B
inhibitors : delay disease progression by a few months
-
centrally acting D1
agonists
-
centrally acting D2
agonists (rapirinol, pramipexol, catergoline and lisuride)
Pergolide has t1/2 = 20 hr, cavergoline = 60 hrs => no fluctuations
in plasma levels, but poor potency (only s.c. apomorphine infusion (t1/2
= 1 hour) is as effective as L-DOPA)
Side effects :
Usually in patients with age < 60 years centrally acting D2
agonists are used before L-DOPA, while in elderlies
the contrary is practiced
-
centrally acting cholinergic agonists
-
M1
antagonists
-
M2
antagonists
-
M3
antagonists
-
M4
antagonists
-
M5
antagonists
-
centrally acting NMDA-R
antagonists (amantadine)
-
centrally acting A2A
antagonists
-
R.O.S. scavengers : vitamin E
and coenzyme Q10, iron chelators
,
zinc
chelators
-
safinamide (SAF) ((S)-(+)-2-(4-(3-fluorobenzyloxy) benzylamino)propanamide)
was initially synthetized by Farmitalia Carlo Erba (Italy). Following initial
anticonvulsant screening, safinamide was selected for its potency, broad
spectrum of action, and good safety margin. Pharmacodynamic properties
probably relevant to its antiepileptic activity are use- and frequency-dependent
block of voltage sensitive Na+ channels, block of Ca++ channels, and glutamate
release inhibition. Possibly contributing mechanism are also selective
and reversible monoamide oxidase B inhibition and dopamine and noradrenaline
uptake inhibition. The high selectivity for the sigma-1 receptor site does
not entail psychotomimetic or behavioral changes. In several experimental
in vitro and in vivo conditions, SAF exerts neurorescuing and neuroprotectant
effects. Safinamide is water soluble and suitable for 1 times a day oral
administration in humans. In a pilot phase II study in 38 refractory epilepsy
patients affected by multiple types of seizures, 41% of subjects obtained
> or =50% seizure reduction during a 12-week escalating dose up to 300
mg 1 times day compared with perspective baseline. Safinamide is being
developed in phase III for treatment of Parkinson's disease, whereas the
development in epilepsy relates to the industrial strategy of the companyref.
-
anti-Alzheimer's
disease (AD)

-
therapy of cognitive disorder
-
direct and indirect cholinergic agonists
-
choline chloride
-
phosphatidylcholine / lecithin
-
AChE
inhibitors (rivastigmine, donepezil, and galantamine)
-
both sage and lemon balm have previously been shown to improve memory and/or
reduce agitation in Alzheimer’s patients : 4 compounds isolated from an
extract of sage root are AChE inhibitors.
-
M1
antagonists
-
M2
antagonists
-
M3
antagonists
-
M4
antagonists
-
M5
antagonists
-
NMDA-R
antagonists : patients with moderate to severe AD who switched to memantine
treatment (20 mg daily) for 52 weeks from their previous placebo therapy
experienced a significant benefit in all main efficacy assessments (functional,
global, and cognitive) relative to their mean rate of decline with placebo
treatment during the double-blind period (P<.05). The completion rate
for the extension phase of the study was high (78%) and the favorable adverse
event profile for memantine therapy was similar to that seen in the double-blind
studyref
-
b-site APP-cleaving enzyme (BACE)
and BACE2
inhibitors
-
Zn chelating agents

-
HMG-CoA inhibitors
can reduce the risk of AD by reducing the production of Ab:
indeed the b-amyloid
precursor protein (APP) / protease nexin-II contains a sphingolipid
binding domain.
-
GABAB
antagonistsref
-
NSAIDs
: some (e.g. indomethacin), but not all, can reduce the risk of AD due
to their ability to reduce Ab42.
Ab42-lowering NSAIDs specifically
affect the proximity between APP and presenilin
1 (PS1) and alter presenilin 1 conformation both in vitro
and in vivo, suggesting a novel allosteric mechanism of actionref
-
Y-27632, a selective NSAID Rock
inhibitor, can reduce Ab42
-
plaque busters : as it is believed that abnormal binding of a metal
ligand in the metal-binding sites of the normal, soluble proteins is a
major factor in the pathogenesis and continued pathology of the resulting
diseases, chelators which cross the blood-brain
barrier (BBB)
,
have potential for therapy or as a recurring prophylactic treatment when
administered at low doses
-
picolinic acid blocks tangle formation in vitro and reverses
it as well better than traditional chelators
-
selective amyloid b42 (Ab42)
lowering agents (SALAs) :
-
MPC-7869 / R-flurbiprofen
(Flurizan™; source : Myriad Genetics,
Inc.). The Phase 2 study showed that patients with mild Alzheimer's
disease who received the 800 mg twice-daily dose of flurizan achieved between
34% and 45% slowing in decline on the 3 primary endpoints (activities of
daily living, overall function and cognitive ability). A > 20% slowing
in decline is generally regarded as clinically significantref.
-
NC-531 (Alzhemed™; source : Neurochem)
is a sulfated glycosaminoglycan mimetic that inhibits amyloid plaque formation.
Phase I clinical trials were ongoing in November 1999, and by October 2002
phase II trials were underwayref.
-
cyclohexanehexol stereoisomers :
when given orally to a transgenic mouse model of AD, inhibit aggregation
of amyloid b peptide (Ab)
into high-molecular-weight oligomers in the brain and ameliorate several
AD–like phenotypes in these mice, including impaired cognition, altered
synaptic physiology, cerebral A pathology and accelerated mortality. These
therapeutic effects, which occur regardless of whether the compounds are
given before or well after the onset of the AD–like phenotype, support
the idea that the accumulation of Ab oligomers
has a central role in the pathogenesis of ADref
-
amyloid-b antagonists : tramiprosate
(Alzhemed®, Cerebril®; source : Neurochem,
Inc.) is a glycosaminoglycan (GAG) mimetic designed to interfere with
the actions of Abeta early in the cascade of amyloidogenic events, also
for the prevention of hemorrhagic stroke caused by cerebral amyloid angiopathy
-
testosterone
replacement therapy improved overall quality of life in patients with AD
while having minimal effects on cognitionref
-
therapy of behavioral disorder
-
atypical antipsychotics (clozapine,
risperidone, olanzapine, quetiapine, ziprasidone, sertindole). Haloperidol
may cause cholinergic impairment and parkinsonism in elderlies. Antipsychotic
drugs do not seem to increase the risk of stroke or other adverse cerebrovascular
events in agitated or psychotic people with AD
-
4% of elderlies with bipolar disorder taking lithium
have Alzheimer's disease, compared with 21% of patients who are not taking
the drug. When mice with NFT are treated with lithium for 5 months, brain
tau levels decrease dramatically (cutting also the number of amyloid plaques)
as inhibition of GSK-3 prevents phosphorylation-induced tangling
-
anti-Huntington's
disease (HD)

-
NMDA-R
antagonists
-
symptomatic treatment
-
anti-amyotrophic
lateral sclerosis (ALS) / Lou Gehrig's disease

-
NMDA-R
antagonists (riluzole) improve survival from 3 to 6 months.
-
kainate
antagonists
-
symptomatic therapy
-
glatiramer acetate
(GA)

-
CNTF

-
N-acetyl-L-aspartyl-L-glutamate
(NAAG) peptidase
inhibitors holds promise for a wide variety of diseases that involve glutamatergic
transmission, and has implications for the diagnosis and therapy of cancer.
This new class of compounds, of which at least one has entered clinical
trials and proven to be well tolerated, has demonstrated efficacy in experimental
models of pain, schizophrenia, amyotrophic lateral sclerosis, traumatic
brain injury and, when appropriately functionalized, can image prostate
cancerref
-
psychotropic
drugs / psychoactive drugs / psychodrugs
-
psycholeptics
-
anti-anxiety / anxiolytics
/ minor tranquilizers / psycholeptics (vs.anxiety
disorders
)
=> myorelaxants
(vs. stroke
,
MS
,
ALS
,
spinal
cord injuries
,
tetanus
,strychnine
poisoning
,
dystonias
)
=> antiseizures
(vs.seizures) => sedatives
(vs. insomnia
)
=> hypnotics /
hypnogenics
-
ethanol

-
p.o. or i.v. GABAA
agonists
-
thiocolchicoside (TCC) (Decontril®, Miotens®,
Muscoril®, Sciomir®, Teraside®,
Tioside®) i.m., a semi-synthetic derivative of the naturally
occurring compound colchicoside,
Side effects : tonic-clonic seizuresref
Contraindications : pregnancy
,
hepatopathies, elderly, cigarette smoking, platelet antiaggregants, and
oral
contraceptives
Side effects : excessive sedation, decrease
of psychomotory performances, hang over, ataxia, paradoxal hyperactivity
in babies
Tolerance to hypnotic effect occurs before
than tolerance to anxiolytic effect.
Acute intoxication : fatigue, sleepiness,
ataxia, systemic
arterial hypotension
,
hypothermy, cognitive impairment (anterograde amnesia, attention deficit
: they are used as experimental model of dementia), dysarthria.
Therapy : flumazenil
and psychostimulants
Addiction risk relates on dose, lasting
of treatment and patient's personality.
Symptoms of abstension crises may vary
from anxiety, insomnia, irritability, nausea, headache
,
palpitations, tremors and sweats, to muscle pain, vomiting, lowering of
sensitive thresholds, up to seizures and depersonalization.
-
sedative H1
antagonists
Side effects : paradoxical effect at high
doses (euphoria => seizures), ataxia, diplopia, anorexia, nausea, vomiting,
constipation or diarrhoea (reduced if administered during meals), partially
parasympatholytics.
-
KCa
inhibitors
-
voltage-gated KCNQ2-5 / KV7.2-5
channel
activators
-
GABAB
agonists
-
RYR1
antagonists
-
bromide : any binary compound of bromine in
which the bromine carries a negative charge (Br–); specifically
a salt (or organic ester) of hydrobromic acid (H+Br–).
Bromides produce depression of the central nervous system, and were once
widely used for their sedative effect. Because overdosage (bromism
)
causes serious mental disturbances they are now seldom used, except occasionally
in grand mal seizures
-
cyclobenzaprine hydrochloride (Flexiban®)
-
tizanidine (TZ) (Mionidin®, Sirdalud®)
-
pridinol mesylate (Lyseen®)
-
tolperisone hydrochloride (Mydocalm®)
-
antipsychotics /
major tranquilizers / neuroleptics / psycholeptics (vs.
psychoses
and mania
)
-
lipophilic D2
antagonists (low affinity)
Side effects :
-
perioral tremor ("rabbit syndrome")
-
irreversible tardive
dyskinesia (TD)
stopping when sleeping => increased risk of suicide
-
oral-facial dyskinesia ("sweet suckling") : this is due to excessive
neurotrophin production by blocked dopaminergic neurons, which in turn
leads to hyperinnervation of buccal muscles.
-
widespread choreoathetosis or tardive
dystonia

-
sedation
-
systemic
arterial hypotension

-
hyperprolactinemia (simulating a prolactinoma
,
hence contraindicated for females in fertile age, although no increased
risk of prolactinoma or mammary carcinoma has been found)
-
rash
-
medullary aplasia
-
cholestasis

-
5-HT2A
antagonists (high affinity) / atypical
antipsychotics
Side effects of clozapine and olanzapine
:
-
D1
antagonists (?)
-
D3
agonists
-
D4
antagonists
-
psychoanaleptics
/ analeptics : exerting a stimulating effect upon
the mind.
-
5-OH-Trp
-
S-AdoMet
-
antidepressants
/ mood-elevating agents / stimulants of mood (vs. depressions
)
-
thymoleptic / antidepressant : any drug that favorably modifies
mood in serious affective disorders such as depression or mania; the main
categories of thymoleptics include the tricyclics
antidepressants, monoamine oxidase inhibitors, and lithium compounds
-
thymeretics
-
ethanol

-
MAO-A
inhibitors (IMAO) : due to irreversible actions of clinically used
IMAO (not RIMA), up to 2 weeks may be required to regenerate fresh MAO
enzyme and restore amine metabolism to normal after discontinuation of
the drugs. Effective also against OCD
and panic attacks
.
Contraindications : assumption of food
containing indirect sympathomimetic amines (e.g. tyramine in seasoned cheeses
("cheese effect"), red wines, smoked food (smoked ham, kippers,
...)), amphetamines
or tricyclic antidepressants may
cause secondary
systemic arterial hypertension
(not with RIMA).
Side effects from hydrazines : peripheral
neuropathies, medullary aplasia, centrolobular hepatitis, weight gain,
sexual dysfunction, edema.
-
tricyclic
antidepressants (TCA)
: any of group of antidepressant drugs that contain 3 fused rings in their
chemical structure and that potentiate the action of catecholamines; the
tricyclic antidepressants include a number of compounds, which may be grouped
into 4 classes on the basis of chemical structure:
-
dibenzazepines
-
dibenzocycloheptadienes
-
dibenzoxazepines
-
dibenzoxepines
Side effects :
-
xerostomia
-
constipation
-
increased appetite
-
hypertonia of detrusor muscle => prostatitis
-
urinary retention in patients with BPH
-
cardiac alterations (arrhtyhmias and dilated cardiomyopathy)
-
noradrenaline reuptake inhibitors (NRI)
/ noradrenaline reuptake inhibitor (NARI / NaRI)
: disinhibiting action
-
selective noradrenalin reuptake inhibitors
(SNRI)

Side effects : secondary
systemic arterial hypertension
-
selective serotonin
reuptake inhibitors (SSRI)
: sedative action. Only fluoxetine has been approved by the FDA to treat
childhood depression : however, physicians regularly prescribe other medications
'off label' to treat depressed children. Almost half of patients with a
unipolar and non-psychotic major depression will not respond to initial
SSRI treatment. Patients who did not respond to SSRI treatment are significantly
more depressed at baseline
Side effects :
-
throat dryness => dry
cough

-
depression of libido
-
increased craving for carbohydrates due to inhibition of 5-HT2C
=> weight gain
-
headache

-
nausea and vomiting
=> weight loss
-
diarrhea

-
transaminitis

-
sleepiness
-
insomnia

-
irritability
-
hyperhidrosis

-
suicide

-
adult suicides linked to popular antidepressantref
-
2-3% of children taking SSRIs in controlled clinical trials experienced
suicidal thoughts and behaviours because of the drugs. The MHRA has issued
warnings about the risk of self harm and suicidal thoughts in young people
taking the drugsref
and the FDA in the USA has also heard reports of similar concernsref.
FDA wants drug companies to post black-box warnings prominently in any
television or magazine advertisements for their products and antidepressants
should also be sold with a guide that tells parents to monitor children
on the drugs for suicidal tendencies. Given the concern about the use of
SSRIs by children and adolescents, it is important for doctors to monitor
closely young adults up to the age of 30 starting or stopping the treatmentref.
-
little information is available on the frequency of SSRI treatment during
pregnancyref
: approximately 4 million live births occur in the USA each year, and about
92,000 of these infants are prenatally exposed to SSRIsref
-
children or unborn babies exposed to fluoxetine could suffer from abnormal
emotional development, animal studies suggest. Rats given the drug
for the first few weeks of life perform poorly on tasks designed to test
their confidence and ability to deal with stress (by placing them in a
cross-shaped maze raised above the floor, a test that measures the willingness
of the animals to explore an unusual environment). Adult rats dosed with
Prozac early in life were less interested in venturing far from their starting
point and spent less time moving around. Animal researchers take this behaviour
as evidence of abnormal emotional development. Related tests revealed that
rats given Prozac are also less willing to take risks to earn rewards such
as food and take longer to escape unpleasant environments, a sign that
they deal poorly with stress. Many pregnant women demand this treatment.
They may otherwise have suicidal thoughts or a desire to kill their infants
after birth. The rats were given a dose comparable to that which humans
receive. The animals received the drugs a few days after birth, the stage
of their development equivalent to the final third of a human pregnancy.
The theory is backed up by studies of rats that have been genetically engineered
to lack the molecules that recycle serotoninref.
These rats have fewer serotonin-producing cells in the brainstem, an area
that controls basic functions such as breathing and that connects widely
to other areas of the brain. The serotonin cells that remain also fire
less frequently than normal. Such rats exhibit behaviour similar to those
in Gingrich's study.
-
the risk of heart defects in babies whose mothers had taken Paxil
early in pregnancy was about 2%, compared to a 1% risk in the whole population.
In another study, the risk of heart defects in babies whose mothers had
taken Paxil in the first 3 months of pregnancy was 1.5%, compared to 1%
in babies whose mothers had taken other antidepressants in the first 3
months of pregnancy. Food and Drug Administration recently published a
public health advisory concerning increased rates of congenital defects
(and, specifically, heart defects) after the use of the SSRI paroxetine
early in pregnancyref
-
neonatal abstinence syndrome, a condition found in infants born
with drug dependencyref
-
Kudos to Eliot Spitzer, New York state's attorney general, for championing
a call for transparency in clinical trial results. In June 2004, Spitzer
sued GlaxoSmithKline (GSK) for concealing negative data on the safety of
its antidepressant Paxil in children. Related lawsuits cropped up elsewhere
in the US and Europe. In August, GSK agreed to release the data on its
website. Combined with the push for clinical trial registries from patient
groups, governments and medical journal editors, GSK's settlement ushered
in a new era of accountability in the pharmaceutical industry.
-
persistent
pulmonary hypertension of the newborn (PPHN)
when used late in pregnancyref
-
serotonin2-antagonists/serotonin
reuptake inhibitors (SARI) / dual serotonergic antidepressants (DSA)

Side effects : priapism
with tradozone
-
selective serotonin noradrenalin
reuptake inhibitors (SSNRI) / serotonin noradrenergic reuptake inhibitors
(SNaRIs)

-
noradrenergic and specific serotonergic
antidepressants (NaSSA)

-
noradrenaline and dopamine reuptake
inhibitors (NDRI)

Side effects : active catabolites, activity
unpredictable by serum levels, decreased catabolism of other drugs catabolized
by CYP2D6
(35% of all current drugs), cholestasis
,
anti-H, anti-D (parkinsonism), parasympatholytic (xerostomia
,
intraocular
hypertension
,
OCD
,
coronary
artery diseases
due to direct cardiotoxicity, secondary
systemic arterial hypertension
,
constipation
,
urinary
retention
)
-
ketamine may be the fastest-acting antidepressant ever tested. 71% f of
17 people with major depression who failed to respond to treatment with
standard antidepressant drugs or more drastic methods, such as electroshock
therapy, felt better the day after taking ketamine, and 35% still felt
better a week later. None improved when dosed with a placeboref.
Most striking was that some patients felt better < 2 hours after taking
ketamine. Currently approved drugs can take weeks to remedy depression.
Large doses of ketamine can cause brain damage in rodents, and its long-term
health effects have not been studied in people. Scientists are currently
testing a wide range of recreationally used-and-abused drugs, including
ecstasy (MDMA) and psilocybin, the active ingredient of magic mushrooms,
as potential therapeutics. Ketamine, invented in 1962 as an anaesthetic,
is chemically related to phencyclidine (PCP), also known as angel dust.
Both induce hallucinations and out-of-body experiences, hence their use
as illegal psychedelics. Ketamine has milder psychotic effects than PCP
and is therefore also used as a legal anesthetic and horse tranquillizer.
Scientists are studying whether it can be used to treat alcoholism and
chronic pain, as well as depressionref.
Ketamine targets NMDA receptor. Existing antidepressants target brain chemicals
such as serotonin, but there is growing evidence that these drugs eventually
affect NMDA receptors. Ketamine may work so quickly because it takes a
short-cut straight to this part of the brain. The psychotic effects of
ketamine, such as euphoria, wore off before the antidepressant effects
kicked in, suggesting that the drug's psychotic and antidepressant effects
are separate. One surprising aspect is that other drugs that induce euphoria,
such as cocaine, usually lead to a depressive crash once the high wears
off. Zarate's group is looking for substances with some of the chemical
properties of ketamine, such as the ability to target NMDA, without the
psychedelic effects. Other scientists have developed drugs that can be
taken with ketamine to damp its side effects. Giving these drugs together
might help patients feel better without getting high.
Tetracyclic antidepressants
include both NaSSA
and RIMA
Inhibition of the target proteins occurs rapidly, but clinical benefits
are usually delayed for 2-4 weeks. The delay may reflect secondary adaptations,
including downregulation of a2
-
and b
-adrenergic
receptors. In the meanwhile anxiolytics can
be co-administered.
Side effects :
-
serotonin syndrome (SS) :
a potentially fatal iatrogenic complication that occurs following concurrent
administration of 2 or more serotonergic agents (e.g. extended-release
venlafaxine
and mirtazapine
(agents that minimally inhibit the CYP2D6
system, which is responsible for tramadol metabolism; also mirtazepine
monotherapyref)
for depression and tramadol (an atypical analgesic that acts in part as
a reuptake inhibitor of serotonin and norepinephrine) for chronic pain)
consisting of sudden onset of 3 or more symptoms involving altered mental
status, autonomic dysfunction, and neuromuscular abnormalities, resolved
over a period of 36 hours after withdrawal. SS is a potentially life-threatening
adverse drug reaction that results from therapeutic drug use, intentional
self-poisoning, or inadvertent interactions between drugs. Three features
of the serotonin syndrome are critical to an understanding of the disorder.
First, the serotonin syndrome is not an idiopathic drug reaction; it is
a predictable consequence of excess serotonergic agonism of central nervous
system (CNS) receptors and peripheral serotonergic receptors. Second, excess
serotonin produces a spectrum of clinical findings. Third, clinical manifestations
of the serotonin syndrome range from barely perceptible to lethalref.
-
cancer : possible effect of TCA and tetracyclic antidepressants on non-Hodgkin's
lymphomaref.
A modest association between 'ever' use of AD and breast cancer was found
using the most parsimonious multivariate model. OR estimates did not change,
but CI were widened and statistical significance lost, after adjustment
for factors associated with breast cancer riskref.
Preclinical studies found evidence for both tumor promotion and suppression,
though the majority of studies predominantly examined TCA, with 1 report
suggesting that TCAs with a nitrogen atom in the central ring are genotoxic.
Of 13 clinical studies, 3 found a significant increase, 4 noted a trend
increase, and 6 found no increase in risk for cancer with antidepressant
(mostly TCA) useref.
-
mood-stabilizing
drugs are used to treat bipolar
disorder (BPD)

-
lithium carbonate (Li2CO3) or
citrate (Eskalith®, Lithobid®, Carbolith®,
Carbolithium®, Contemnol®, Duralith®,
Hypnorex®, Lentolith®, Liskonum®,
Litarex®, Lithane®, Lithicarb®,
Lithizine®, Maniprex®, Milithin®,
Neurolepsin®, Neurolithium®, Phasal®,
Quilonorm®, Teralithe®) (at 0.5-0.8 mEq /
L : 80% efficacy) acts as ..
-
inducer of neurotensin
expression in catecholaminergic neurons
-
BPNT1
inhibitor
-
inositole phosphate phosphatase
inhibitor
-
GSK-3b
inhibitor. Phosphate molecules then attach to GSK-3, deactivating the
enzyme further12. In turn, this affects the expression of the various genes
influenced by GSK-3 levels. A month's treatment boosts the volume of total
grey matter by an average of 3%. The drug may do this by prompting the
production of new neurons, a process that some researchers believe involves
GSK-3 : Li stimulates neural
stem cells (NSC)
in culture, causing them to multiply faster. But lithium boosts levels
of N-acetyl aspartate, a marker for healthy cells in grey matter.
This suggests that the drug could be protecting cells in patients with
BPD, instead of, or as well as, prompting the growth of new neurons.
Biphasic clearance with fast (4-6 hours) and slow phases (monitor blood
level during the latter one).
Contraindications : pregnancy
Side
effects
-
anticonvulsant agents / anti-epileptic
drugs (AED) (p.o.) (vs. seizures
)
work by increasing GABAergic neurotransmission and decreasing glutamatergic
neurotrasmission. Carbamazepine and valproate are teratogenic and should
not be used in pregnants.
-
GABAA
agonists (phenobarbital)
-
indirect GABA agonists
-
voltage-gated Na+ channel
blockers (therapeutic range for carbamazepine is 4-12 mg/mL,
obtained with 10-20 mg/kg/die in 3-4 doses)
-
voltage-gated T-type Ca2+
channel

-
voltage-gated KCNQ2-5 / KV7.2-5
channel
activators : also used for neuropathic pain, hyperalgesia and allodynia,
and anxiety : therapeutic dose range (600-1200 mg/day). No tolerance, dependence
or withdrawal potential has been reported, although adverse effects can
include mild dizziness, headache, nausea and somnolence. Thus, retigabine
may prove to be useful in the treatment of a diverse range of disease states
in which neuronal hyperexcitability is a common underlying factorref.
-
unknown mechanism blockers (CCB)
-
felbamate (Felbatol®)
-
levetiracetam (Keppra®)
AEDs are commonly prescribed for nonepileptic conditions, including migraine
headache, chronic neuropathic
pain
,
mood
disorders
,
schizophrenia
and various neuromuscular syndromes. In many of these conditions, as in
epilepsy, the drugs act by modifying the excitability of nerve (or muscle)
through effects on voltage-gated sodium and calcium channels or by promoting
inhibition mediated by GABAA
receptors. In neuropathic pain, chronic nerve injury is associated with
the redistribution and altered subunit compositions of sodium and calcium
channels that predispose neurons in sensory pathways to fire spontaneously
or at inappropriately high frequencies, often from ectopic sites. AEDs
may counteract this abnormal activity by selectively affecting pain-specific
firing; for example, many AEDs suppress high-frequency action potentials
by blocking voltage-activated sodium channels in a use-dependent fashion.
Alternatively, AEDs may specifically target pathological channels; for
example, gabapentin is a ligand of a2d
voltage-activated calcium channel subunits that are overexpressed in sensory
neurons after nerve injury. Emerging evidence suggests that effects on
signaling pathways that regulate neuronal plasticity and survival may be
a factor in the delayed clinical efficacy of AEDs in some neuropsychiatric
conditions, including bipolar
affective disorder
ref.
Side effects :
-
lamotrigine has been associated with labiopalatoschisis

-
suppression of nerve cell activity, required to form connections and thrive
in a baby's growing brain, leads to neuronal apoptosis. Experiments on
immature rats' brains suggest that treating epileptic children with benzodiazepine
drugs could do more harm than good. The neurotransmitters unlocked by these
drugs cause changes in brain chemistry that actually promote epileptic
activity. Anticonvulsant benzodiazepines are a last-ditch treatment used
to stop seizures in both infants and adults. Some medical experts think
that the electrical activity associated with seizures can change brain
networks, making them more susceptible to future epileptic activity. Benzodiazepine
drugs enhance the action of GABA in the immature hippocampus removed from
baby rats, which triggers rapid electrical signalling in the immature hippocampus
- a hallmark of epileptic seizures. Conversely, GABAA antagonists
seemed to prevent repeated seizures in the rats' brains. About a third
of the 2.7 million epileptics in the USA are 17 or younger : a high-fat,
low-carbohydrate diet reduces seizures in children with intractable epilepsy.
60-70% of kids with epilepsy don't have effective treatment options. Although
benzodiazepine treatment is relatively rare, medics should still look more
closely at the use of drugs that enhance GABA signalling : too much GABA
signalling in the very young can make chloride ions build up in immature
neurons, predisposing them to further epilepsy. The adult brain is probably
very different : there, GABA inhibits the fast electrical signalling associated
with adult epilepsy. This may be connected with changes in the way chloride
ions are transported in and out of neurons as the brain grows older. Doctors
should also investigate whether pregnant women taking benzodiazepines could
be predisposing their children to epilepsyref
-
several cutaneous and hematological adverse reactions have been observed
during carbamazepine therapy. The various cutaneous eruptions caused by
carbamazepine include morbilliform eruptions, urticaria, erythroderma,
purpura, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal
necrolysis, drug induced lupus, and photosensitivity. Various hematological
side effects of carbamazepine include leukocytosis, persistent leucopenia,
eosinophilia, agranulocytosis
,
aplastic
anemia
,
and thrombocytopenia. The incidence of hematological reactions to carbamazepine
has been estimated to range between 1:10,800 to 1:38,000 per year
-
anti-psychological
dependence drugs
-
DAT
inhibitors : a form of SLC6A3
and a variant of D3
appear
to ease the difficulty of kicking the habit of tobacco smoking
-
D3
antagonists or partial agonists
-
mecamylamine has been used since the 1950s to combat high blood
pressure. But the drug also affects the brain - it reduces the release
of a pleasure chemical called dopamine, which dulls the addictive effects
and cravings associated with drugs such as nicotine and alcohol.
-
psychotonic
/ nervous reconstituents
-
psychostimulants
/ strimulants of alertness : they act by ...
-
activating excitatory circuits : indirect orthosympathomimetics
-
psychomotor drugs : pertaining to motor
effects of cerebral or psychic activity.
-
nootropic drugs : promoting the enhancement
of cognition and memory and the facilitation of learning
-
amphetamines

-
ephedrine
.
Some athletes have advocated the use of ephedra-containing dietary supplements
as performance-enhancing agents. On December 31, 2003, federal officials
announced plans to ban ephedra immediately. Health and Human Services Secretary
Tommy Thompson told reporters, "The time to stop using these products is
now." This action followed several high-profile catastrophic outcomes linked
to ephedra products, including the death of 23-year-old Baltimore Orioles
pitcher Steve Bechler. Published studies reported that sales of ephedra-containing
supplements represented < 1% of all dietary-supplement sales but that
these products accounted for 64% of the serious adverse reactions to supplements
reported to the Centers for Disease Control and Preventionref.
Unfortunately, in April 2005, a federal court in Utah struck down the federal
ban on ephedra. Many companies that make these products are located in
Utah
-
cocaine

-
pemoline

-
adrafinil (Olmifon®)
-
modafinil (Modiodal®, Provigil®, Alertec®,
Modiodal®)
-
inhibiting inhibitory circuits
-
purinergic receptors
antagonists
-
GABAA
antagonists
-
Gly receptor
antagonists
-
pipradol (Meratran®)
-
centrophenoxine (Cerutil®, Helfergin®,
Lucidril®)
-
nikethamide (Coramine®)
-
doxapram (Dopram®, Stimulexin®)
-
ethamivan (Emivan®)
-
pentylenetetrazol (Metrazol®)
-
bemegride (Megimide®)
-
mefexamide (Timodyne®, Perneuron®)
Therapeutic indications :
-
for CNS diseases
-
for diseases not involving CNS
Alertness drug arouses fears about 'lifestyle' misuse : 'Brain booster'
found to reverse effects of sleep deprivationref
Dose-dependent side effects (related to
individual sensitivity, environment (noises, temperature) and interaction
with other drugs or current diseases) :
-
acute overdose
-
CNS : euphoric syndrome (hyperactivity) => dysphoric syndrome
(anxiety, apathy, melancholy, anorexia, insomnia, hypersomnia, parasomnia)
=> paranoideal psychosis (delirium, hallucinations, illusion of
parasitoses, irritability) => cerebral
edema
,
ischemic
stroke
,
lobar
cerebral parenchymatous hemorrhages
,
anosmia
,
acute
neuropathy
,
extraotogenous
tinnitus
,
epilepsy
=> death due to effects on...
-
cardiovascular apparatus : secondary
systemic arterial hypertension
(+ 5 mmHgref)
and secondary
vascular pulmonary arterial hypertension
=> pulmonary
edema
,
tachyarrhythmias
=> cardiac
and respiratory standstill. On February 9, 2006, a Food and Drug Administration
(FDA) advisory panel recommended that stimulant drugs prescribed for attention
deficit–hyperactivity disorder (ADHD) carry warnings about the potential
for an increased risk of sudden death and cardiovascular problems such
as hypertension, cardiac arrest, arrhythmias, and stroke. Stimulant drugs
are known to cause adverse cardiovascular effectsref
and 188 hospital admissions were reported in USA since Aug 1, 2003 to Dec
31, 2005ref
Acute overdose therapy :
-
chronic abuse (due to reverse tolerance !)
-
increase of basal metabolism due to orthosympathetic hypertone
-
CNS : paranoideal
psychoses
,
subarachnoid
hemorrhages
,
rupture of brain aneurysms
,
epilepsy
,
hyperthermia
,
anorexia
-
GI tract : decrease of gastric and intestinal secretions, liver steatosis
=> hepatitis
-
respiratory apparatus : atrophic
rhinitis
,
nasal
septal perforation
,
chronic
bronchitis
-
cardiovascular apparatus : arrhythmias
,
AMI
,
toxic
myocarditis
,
ascending
aorta aneurysms
and ruptures, vasculitis
,
intestinal
ischemias
-
madarosis
from cocaine
Chronic abuse therapy :
-
psychodysleptics
-
cerumenolytics
: dispersion of impacted ear wax / cerumenref
-
sodium bicarbonate and docusate sodium (Colace®, Waxsol®)
disperse wax within 2 hours
-
Arachis oil + p-dichlorobenzene + chlorbutol (Cerumol®)
is much slower
-
olive oil has no effect
-
urea hydrogen peroxide (Exterol®)
-
Otocerol®)
-
choline salicylate + glycerin (Audax®)
-
almond oil + Arachis oil + camphor oil (Earex®)
-
triethanolamine polypeptide (Cerumenex®)
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