Antipsychotic Drugs
Introduction
- Antipsychotic Drugs (Neuroleptics / Major tranquilizers / Ataractic / psychotropic drugs) are used to treat psychoses (primarily to treat schizophrenia, but they are also effective in other psychotic and manic states). These are drugs having a salutary therapeutic effect in psychoses.
- Antipsychotic drugs are not curative and do not eliminate chronic thought disorders, but they often decrease the intensity of hallucinations and delusions and permit the person with schizophrenia to function in a supportive environment.
- All of the first-generation and most of the second-generation antipsychotic drugs block D2 dopamine receptors in the brain and the periphery. Most of the secondgeneration agents appear to exert part of their unique action through inhibition of serotonin receptors (5-HT), particularly 5-HT2A receptors.
Classification
Antipsychotic drugs can be classified as follows:
1. First Generation (Typical) antipsychotics
- First Generation (Typical / conventional / traditional ) antipsychotics are competitive inhibitors at a variety of receptors, but their antipsychotic effects reflect competitive blocking of dopamine D2 receptors.
- First-generation antipsychotics are more likely to be associated with movement disorders known as extrapyramidal symptoms (EPS), particularly drugs that bind tightly to dopaminergic neuroreceptors, such as haloperidol.
- No one drug is clinically more effective than another.
- E.g.
[wpsm_comparison_table id=”33″ class=””] - Chlorpromazine & Thioridazine are considered as low potency first generation antipsychotics while rest are high potency first generation antipsychotics. This classification does not indicate clinical effectiveness of the drugs, but rather specifies affinity for the dopamine D2 receptor, which, in turn, may influence the adverse effect profile of the drug.
2. Second Generation (Atypical) antipsychotics
- Second-generation antipsychotic drugs are newer antipsychotics that have weak D2 blocking but potent -HT2 antagonistic activity.
- They have a lower incidence of EPS than the first-generation agents but are associated with a higher risk of metabolic side effects, such as diabetes, hypercholesterolemia, and weight gain.
- The second- generation drugs appear to owe their unique activity to blockade of both serotonin and dopamine and, perhaps, other receptors.
- Second-generation agents are generally used as first-line therapy for schizophrenia to minimize the risk of debilitating EPS associated with the first-generation drugs that act primarily at the dopamine D2 receptor.
- The second-generation antipsychotics exhibit an efficacy that is equivalent to, and occasionally exceeds, that of the first-generation antipsychotic agents.
- E.g.
[wpsm_comparison_table id=”34″ class=””]
Therapeutic usage
Antipsychotic drugs can be used clinically in following way:
- Indicated as anti-psychotic drug for treating psychoses particularly Schizophrenia.
- Can be used for the treatment of schizoaffective disorder.
- Can be for the management of the manic and mixed symptoms associated with bipolar disorder.
- Can be used as anti-emetic agent thus, useful in the prevention of nausea and vomiting, particularly treatment of drug-induced nausea. They effective in morning sickness but not in motion sickness.
- May be used as Sedative.
- Can be used as tranquilizers to manage agitated and disruptive behavior secondary to other disorders.
- May relieve anxiety.
- May be used for Organic brain syndromes on a short-term basis.
- To potentiate hypnotics, analgesics and anaesthetics (Justified only in anaesthetic practice).
- May be indicated in Alcoholic hallucinosis, Huntington’s disease and Gilles de Ia Tourette’s syndrome.
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