Hyperpyrexia, with antipsychotics

Neuroleptic malignant syndrome (NMS) A potentially fatal symptom complex sometimes referred to as NMS has been reported in association with promethazine alone or in combination with antipsychotic drugs. Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status, and evidence of autonomic instability (eg, irregular pulse or blood pressure, tachycardia, diaphoresis, cardiac dysrhythmias). 

In temperature extremes, patients taking antipsychotics may experience their body temperature adjusting to ambient temperature (poikilother-mia). Hyperpyrexia can lead to heat stroke. Hypothermia is also a risk, particularly in elderly patients. These problems are more common with the use of low-potency FGAs. 

Neuroleptic malignant syndrome is a rare condition which can occur even after the single administration of antipsychotics. It manifests itself with hyperpyrexia, muscle rigidity, autonomic symptoms, clouding of consciousness and it has a mortality rate of over 10%. The aetiology is unknown but dopamine blockade may play a role. 

Tricyclic antidepressants are notorious for their risk to be involved in drug-drug interactions. Additive anticholinergic effects can be expected in combination with antihistamines, antipsychotics and anticholinergic-type anti-Parkinson agents. Hepatic enzyme-inducing agents increase their hepatic metabolism while enzyme inhibitors may potentiate the effects of tricyclics. Concomitant use with monoamine oxidase inhibitors will produce hypertension, hyperpyrexia and convulsions. 

---