Pathogenesis and treatment of neuroleptic malignant syndrome.

1. Neuroleptic drugs (antipsychotics) produce numerous side effects which include serious extrapyramidal symptoms consisting of akathisia, dystonia, neuroleptic malignant syndrome, parkinsonian reactions such as postural abnormality, tremor, akinesia or bradykinesia, rigidity, and tardive dyskinesia. 2. Among the complications of neuroleptic chemotherapy, the most serious and potentially fatal complication is malignant syndrome, which is characterized by extreme hyperthermia, "lead pipe" skeletal muscle rigidity causing dyspnea, dysphagia, and rhabdomyolysis, autonomic instability, fluctuating consciousness, leukocytosis, and elevated creatine phosphokinase. 3. Neuroleptic malignant syndrome should be differentiated from malignant hyperthermia, lethal catatonia, and other pathological states producing some of these same symptoms. 4. In addition to neuroleptics, malignant syndrome has been caused by thymoleptics (antidepressants), metoclopramide (antiemetic), metoclopramide combined with cimetidine, tetrabenazine, overdosage of benzodiazepine, phenelzine, dothiepin and alcohol, and amphetamine. 5. Factors leading to and/or facilitating the emergence of neuroleptic malignant syndromes are reportedly organic brain syndrome, dehydration, exhaustion, external heat load, excessive sympathetic discharge, use of long acting neuroleptics, high doses of neuroleptics, rapid dose titration with neuroleptics, abrupt discontinuation of antiparkinsonism agents, and concurrent lithium therapy. 6. Although, the pathogenesis of neuroleptic malignant syndrome is not understood completely, a blockade of dopaminergic receptors in the hypothalamus, spinal cord and striatum, an alteration of dopaminergic-serotonergic transmission in the body, an enhanced synthesis and action of prostaglandin E1 and E2, and a modification of calcium-mediated signal transduction in the body have been suggested. 7. The treatment of malignant syndrome includes immediate withdrawal of neuroleptic drugs, i.v. infusion of dantrolene, and oral administration of bromocriptine; or alternatively i.v. infusion of dantrolene and the combination of levodopa-carbidopa. 8. Other measures to enhance the therapeutic effectiveness of the aforementioned regimens are to include the use of anticholinergic drugs such as benztropine to enhance the effectiveness of bromocriptine, of lorazepam if catatonic symptoms persist, or of electroconvulsive therapy (ECT) if psychotic symptoms persist. 9. These treatments, however, must be "active" rather than "passive", in order to avert fatalities and/or unfortunate sequelae from this iatrogenic and incompletely understood disease.