Download Atypical Antipsychotic Drugs: Clozapine, olanzapine

ANTI-PSYCHOTICS
These are also called as major tranquillizers or neuroleptics. These are the drugs, which
are used to treat psychosis, including schizophrenia and mania caused by bipolar disorder. They
can also be used to treat severe depression and severe anxiety. A drug may be classified by the
chemical type of the active ingredient or by the way it is used to treat a particular condition.
Antipsychotics are classified as typical or atypical. Atypical antipsychotics are the recently
developed drugs that are useful in patients that do not respond to treatment with other typical
antipsychotics.
Symptoms: Grandiosity or paranoia, hallucinations and delirium.
Mechanism of action: Antipsychotics act by blocking dopamine receptors in the brain and
interfering with dopaminergic transmission and altering the effect of certain chemicals in the
brain, called dopamine, nor-adrenaline serotonin, and acetylcholine. These chemicals have the
effect of changing the mood, behavior and emotions.
Drug therapy:
1. Phenothiazines: Chlorpromazine, fluphenazine, thioridazine, triflupromazine
2. Butyrophenones: Haloperidol, trifluperidol
3. Thioxanthines: Chlorprothixene, thiothixene
4. Indolic derivatives: Molindone
5. Atypical antipsychotics: Clozapine, risperidone, olanzepine
6. Miscellaneous: Oxypertine, pimozide, penfluridol, tetrabenazine
Phenothiazine Derivatives: Based on the primarily side chain of the molecule, phenothiazines
are classified as; Aliphatic derivatives (Eg, chlorpromazine) and piperidine derivatives (Eg,
thioridazine) are the least potent. These drugs produce more sedation and weight gain. Piperazine
derivatives are more potent (effective in lower doses) but not necessarily more efficacious.
Butyrophenone Derivatives: Haloperidol, a butyrophenone, is the most widely used typical
antipsychotic drug, despite its high level of EPS relative to typical antipsychotic drugs.
Diphenylbutylpiperidines are closely related compounds. The butyrophenones and congeners
tend to be more potent and to have fewer autonomic effects but greater extra-pyramidal effects
than phenothiazines.
Thioxanthene Derivatives: Thiothixene belongs to a group of drugs called antipsychotics,
which work by altering the activity of certain natural substances in the brain. Thiothixene is a
prescription medication used to treat schizophrenia.
Adverse effects: Dizziness, drowsiness, uncontrolled muscle movement, a fast heart beat,
fainting, low blood pressure.
Pimozide and molindone: These are the typical antipsychotic drugs. There is no significant
difference in efficacy between these newer typical and the older typical antipsychotic drugs.
Atypical Antipsychotic Drugs:
antipsychotic drugs.
Clozapine, olanzapine, risperidone, sertindole are atypical
Clozapine is the prototype. Risperidone is rapidly converted to 9-
hydroxyrisperidone in vivo in most patients, except for about 10% of patients who are poor
metabolizers. These drugs have complex pharmacology but they share a greater ability to alter
5-HT 2A -receptor activity than to interfere with D 2 -receptor action. In most cases, they act as
partial agonist at the 5-HT1A receptor, which produces synergistic effects with 5-HT2A receptor
antagonism. Most are either 5-HT6 or 5-HT7 receptor antagonists.
Pharmacokinetics: Most of the antipsychotic drugs are readily but incompletely absorbed, many
undergo significant first-pass metabolism. Most antipsychotic drugs are highly lipid soluble and
protein bound (92–99%). Metabolites of chlorpromazine may be excreted in the urine.
Side effects: Dry mouth, flushing, blurred vision and constipation, sedation, Weight gain,
diabetes and heart problems.