Antipsychotic drugs extrapyramidal acute

Extrapyramidal symptoms (EPS) Dystonic reactions develop primarily with the use of traditional antipsychotics. EPS has occurred during the administration of haloperidol and pimozide frequently, often during the first few days of treatment. Neuroleptic malignant syndrome (NMS) A potentially fatal symptom complex sometimes referred to as NMS has been reported in association with administration of antipsychotic drugs. Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status, and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, cardiac dysrhythmia). Additional signs may include elevated creatine phosphokinase, rhabdomyolysis, and acute renal failure. 

Some of the H antagonists, especially diphenhydramine, have significant acute suppressant effects on the extrapyramidal symptoms associated with certain antipsychotic drugs. This drug is given parenterally for acute dystonic reactions to antipsychotics. 

Holloman LC, Marder SR. Management of acute extrapyramidal effects induced by antipsychotic drugs. Am J Health Syst Pharm 1997 54 2461-2477. 

Adverse Neurological Effects Many neurological syndromes, particularly involving the extrapyramidal motor system, occur following the use of most antipsychotic drugs, especially with the high-potency D -receptor antagonists (tricyclic piperazines and butyrophenones). Acute adverse extrapyramidal effects are less likely with aripiprazole, clozapine, quetiapine, thioridazine, and ziprasidone, or low doses of olanzapine or risperidone. 

Because of multiple receptor actions, which occur at different concentrations, different neuroleptics have different action profiles. There are many classifications for neuroleptic drugs, the least useful of which is probably based on their chemical structure. Other classifications include linear classifications based on the propensity to cause EPS, or multidimensional ones such as the Liege star which combines information on three positive effects (anti-autistic, antiproductive, antipsychotic), and three negative (hypotensive, extrapyramidal, sedative). In a general way, the more sedative neuroleptics such as levomepromazine, used more to treat acute agitation states, cause more hypotension related to alpha blockade, whereas those that act best on delirium (productive states) such as haloperidol tend to cause more EPS. 

Haloperidol is used as an antipsychotic and occasionally for control of acute agitation in the intensive care unit. It is can also be useful in the treatment of phencyclidine abuse. It produces a cataleptic state with little drowsiness and has minimal effects on blood pressure and respiration. It is a long-acting drug with a half-life of about 18 hours. It is available in oral and injectable preparations. In large doses extrapyramidal side effects may occur. 

Extrapyramidal symptoms. All classical antipsychotics are capable of producing these effects because they act by blocking dopamine receptors in the nigrostriatal pathway. The result is that some 75% of patients experience extrapyramidal symptoms which may appear shortly after starting the drug or increasing its dose (acute effects), or some time after a particular dose level has been established (tardive effects, see p. 387). 

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