This list might not be inclusive of all serious or fatal syndromes or side effects but it includes the essential ones being associated with some antipsychotics and some anesthesia medications that residents and board exam takers should be aware of:
Neuroleptic Malignant Syndrome (NMS)
A rare but dangerous reaction to dopamine blockade, usually from antipsychotics (haloperidol, risperidone, fluphenazine). It develops gradually over 1–3 days. Classic signs: lead‑pipe rigidity, hyperthermia, autonomic instability, and markedly elevated CK from muscle breakdown. Mental status changes (agitation → stupor) are common. Treatment centers on stopping the drug, aggressive cooling, IV fluids, and sometimes dantrolene or bromocriptine.
Serotonin Syndrome
A fast‑onset toxicity from excess serotonin, often triggered by combining SSRIs/SNRIs with MAOIs, tramadol, linezolid, MDMA, or triptans. Symptoms appear within hours, not days. Key features: hyperreflexia, clonus (especially inducible or ocular), agitation, tremor, diaphoresis, and fever. The hallmark difference from NMS is neuromuscular hyperactivity, not rigidity. Management includes stopping serotonergic agents, supportive care, benzodiazepines, and sometimes cyproheptadine.
Malignant Hyperthermia (MH)
A genetic, anesthesia‑triggered crisis caused by volatile anesthetics (e.g., sevoflurane) or succinylcholine. Onset is minutes, often during surgery. Hallmarks: rapidly rising CO₂, severe muscle rigidity, hyperthermia, tachycardia, and metabolic acidosis. It is a RYR1 mutation–linked disorder of calcium release in skeletal muscle. Immediate treatment is IV dantrolene, cooling, and stopping the triggering agent.
Malignant Catatonia
A severe form of catatonia that becomes life‑threatening. It presents with fever, autonomic instability, rigidity, mutism, and agitation, often resembling NMS. The key clue is a psychiatric catatonic state preceding the autonomic collapse. Treatment relies on benzodiazepines (lorazepam) and ECT, not antipsychotics.
Anticholinergic Toxicity (Severe Form)
Not always labeled “malignant,” but can be fatal. Caused by overdose of anticholinergic agents (TCAs, antihistamines, antipsychotics like clozapine). Presents with hyperthermia, dry skin, dilated pupils, urinary retention, ileus, delirium, and tachycardia. The skin is dry, unlike serotonin syndrome or NMS. Severe cases may require physostigmine under strict monitoring.
Malignant Hypertension (Drug‑Induced)
Can occur with MAOIs when combined with tyramine‑rich foods or sympathomimetics. Sudden, severe BP elevation leads to headache, chest pain, vision changes, and risk of stroke. Management includes rapid BP control with IV antihypertensives and stopping the offending agent.
Quick Differentiation Snapshot:
NMS: slow onset, lead‑pipe rigidity, high CK, dopamine blockade.
Serotonin Syndrome: fast onset, clonus + hyperreflexia, serotonergic excess.
Malignant Hyperthermia: anesthesia‑triggered, rapid CO₂ rise, rigidity, genetic.
Malignant Catatonia: psychiatric catatonia + fever/autonomic collapse.
Anticholinergic Toxicity: dry skin, delirium, hyperthermia, urinary retention.
Malignant Hypertension: MAOI‑related, severe BP spike.