Psychotomimetic drugs
Also
referred as hallucinogens which affect thought, perception and mood without
causing marked psychomotor stimulation or depression
Psychotomimetic
drugs fall broadly into 2 groups:
o Drugs that act on
5-HT transporter or receptors
§
agonist
at 5-HT2 receptors (LSD, psilocybin, mescaline)
§
inhibitor
of 5-HT uptake (MDMA)
o Antagonists at
NMDA-type glutamate receptors (PCP)
Toxicity/overdose
Depends
on the individual drugs
1
Tissue toxicity - some are neurotoxic
2
Psychic toxicity - acute transient psychosis, flash backs
3
Behaviour toxicity - distorted behaviour, aggressive, violent
Hallucinogens
withdrawal
These
drugs do not cause physical dependence, but they have tremendous abuse
potential (psychological dependence).
LSD, Psilocybin &
Mescaline
They
are exceptionally potent psychotomimetic drug
Lysergic
acid diethylamide (LSD) occurs in the fungus ergot
Mescaline
is derived form Mexican cactus while Psilocybin is obtained from fungus,
similar properties to LSD
Their
main effects are on mental function (most notably alteration of perception in
such a way that sights and sounds appear distorted and fantastic)
Hallucinations
which include visual, auditory, tactile and olfactory aspect also occur.
Sensory
modalities may become confused - that sounds are perceived as visions
Thought
processes tend to become illogical and disconnected.
LSD
appears to act as an agnoist at 5-HT2 receptors and suppresses electrical
activity in 5-HT raphe nuclei.
LSD
is exceptionally potent, producing a long-lasting sense of dissociation and
disordered thoguht, sometimes with frightening hallucinations and paranoid
delusions (bad trip) which can lead to violence
Hallucinatory
epsiodes can recur even after a long interval
Activation
of the sympathetic nervous system causes pupillary dilation, hypertension,
piloerection and hyperthermia
LSD
may precipitate schizophrenic attacks in suspetible patients
MDMA
MDMA
is an amphetamine derivate which is a powerful psychomotor stimulant &
psychotomimetic
MDMA
works by inhibiting monoamine transporter especially the serotonin transporter,
which bring the net effect of large increase in free serotonin in certain brain
regions.
Research
in animals links MDMA exposure to long-term damage to neurons that are involved
in mood, thinking, and judgement.
MDMA effects
They
have many effects similar to amphetamines.
Chronic
users of MDMA are found to perform more poorly than nonusers on certain types
of cognitive or memory tasks.
The
after effect of MDMA persist for few days and comprise depression, anxiety,
irritability, increased aggression - also kown as 'midweeek blues'
At
high doses, MDMA can interfere with one body's ability to regulate temperatue
leading to hyperthermia which results in kidney, liver and cardivascular system
failure)
MDMA
is able to interfere with its own
metabolism, potentially harmful levels can be reached by repeated drug use
within short intervals.
Phencyclidine
Phencyclidine
is also known as PCP or 'angel dust'. Its effect resemble other psychotomimetic
drugs but also include analgesia.
Phencyclidine
main pharmacological action is to block the NMDA receptor channel in cortex and
limbic system. It produces hallucinations which is the desired effect, however,
detachment, disorientation and violent behavior may occur. Phencyclidine can be
fatal in overdose.
PCP effects
At
low dose, it can cause dreamlike, carefree state, mood elevation, heightened or
altered perception.
Adverse
effects are impaired judgment, mood swings and partial amnesia
At
moderate dose, it induces inebriation, dissociation, depersonalization,
perceptual distortion, diminished pain sensitivit.
Adverse
effects are ataxia, motor impairment, confusion, disorientatoin, abnormal body
sensations, amnesia, exaggerated mood swings, panic
At
high dose, it may cause all of the above effect mentioned plus hallucinations
Adverse
effects are catatonia, 'blank' stare, delirium, severe motor impairment,
psychotic behavior, hypertensive crisis.
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