Drugs depressing antipsychotic agents

Drugs that may interact with antipsychotics include alcohol, CNS depressants, antihypertensive agents, dopamine, epinephrine, and charcoal. 

There are some clinically important pharmacodynamic drug-drug interactions to be mentioned. Antipsychotics will potentiate the central depressant effects of sedatives and of alcohol. They will also increase the risk of respiratory-depressant effects of opiates. Inducers of drug metabolic enzymes like for example rifampicin and several antiepileptics, may increase the elimination rate of antipsychotic agents and thus decrease their efficacy. 

Schizophrenia is the primary indication for antipsychotic agents. Antipsychotic drugs are also used very extensively in patients with psychotic bipolar disorder (BP1), psychotic depression, and treatment resistant depression. 

These and other nonreceptor elements of the calcium-phosphoinositide signaling pathway are now becoming targets for drug development. For example, the therapeutic effects of lithium ion, an established agent for treating manic-depressive illness, may be mediated by effects on the metabolism of phosphoinositides (see Chapter 29 Antipsychotic Agents Lithium). 

Antipsychotic drugs include the older phenothiazines and butyrophenones, as well as newer atypical drugs. All of these can cause CNS depression, seizures, and hypotension. Some can cause QT prolongation. The potent dopamine D2 blockers are also associated with parkinsonian-like movement disorders (dystonic reactions) and in rare cases with the neuroleptic malignant syndrome, characterized by "lead-pipe" rigidity, hyperthermia, and autonomic instability (see Chapter 29 Antipsychotic Agents Lithium). 

ANTIMANIC AGENTS are used mainly to treat manic-depressive illness (bipolar disorder), which is characterized by periods of mood normality punctuated by episodes of mania and bouts of depression. The manic phase most often requires acute treatment, and initially ANTIPSYCHOTIC AGENTS, e.g. phenothiazines, will usually be given. Thereafter, a very different psychoactive drug, lithium, may gradually be substituted in most patients, and this can prevent or reduce... 

Neuroleptic. A drug producing symptoms similar to those of depressant diseases of the central nervous system (CNS). Frequently used to refer to an antipsychotic agent. 

The psychotic disorders include schizophrenia, the manic phase of bipolar (manic-depressive) illness, acute idiopathic psychotic illnesses, and other conditions marked by severe agitation. All exhibit major disturbances in reasoning, often with delusions and hallucinations. Several classes of drugs are effective for symptomatic treatment. Antipsychotic agents also are useful alternatives to electroconvulsive therapy (ECT) in severe depression with psychotic features, and sometimes are used in the management of patients with psychotic disorders associated with delirium or dementia or induced by other agents (e.g., stimulants or L-DOPA). 

Contraindications for antipsychotic therapy are few they may include Parkinson s disease, hepatic failure, hypotension, bone marrow depression, or use of CNS depressants. Overdoses of antipsychotics are rarely fatal, except for thioridazine, which is associated with major ventricular arrhythmias, cardiac conduction block, and sudden death. For other agents gastric lavage should be attempted even if several hours have elapsed since the drug was taken, because gastrointestinal motility is decreased and the tablets may still be in the stomach. Moreover, activated charcoal effectively binds most of these drugs and can be followed by a saline cathartic. The hypotension often responds to fluid replacement or pressor agents such as norepinephrine. 

The antidepressant properties of these earlier antidepressants were chance discoveries. Imipramine was first developed as a potential antipsychotic, but when Kuhn (2) tested the clinical efficacy of this agent, he found that it only benefited depressed schizophrenic patients. This observation prompted him to test it in patients who were suffering from melancholia. Iproniazid was developed as an antitubercular drug, but the observation that euphoria was a side effect led George Crane ( 3) to conduct clinical trials, which found it useful in purely depressed patients. A year later, Nathan Kline ( 4), following up on this observation, reported positive results when he administered iproniazid to another depressed group. 

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