Write a short note on antipsychotic-induced extrapyramidal side effects, including acute dystonia.
Mechanism
Antipsychotics block dopamine D2 receptors. Therapeutic benefit comes from blockade in the mesolimbic pathway, but blockade in the nigrostriatal pathway produces extrapyramidal side effects (EPS), and blockade in the tuberoinfundibular pathway causes hyperprolactinaemia. Risk is highest with high-potency typical agents — haloperidol, fluphenazine, trifluoperazine — and lower with atypicals, of which clozapine and quetiapine carry the least risk.
Types of Extrapyramidal Side Effect
| Syndrome | Onset | Features | Treatment |
|---|---|---|---|
| Acute dystonia | Hours to days | Sustained muscle spasm — oculogyric crisis, torticollis, trismus, opisthotonus, laryngospasm | Anticholinergic — promethazine, benztropine or trihexyphenidyl, given parenterally; response within minutes |
| Akathisia | Days to weeks | Subjective inner restlessness with inability to sit still; often mistaken for worsening psychosis | Reduce dose; propranolol; benzodiazepine; switch agent |
| Parkinsonism | Weeks to months | Bradykinesia, rigidity, coarse rest tremor, mask-like facies, shuffling gait | Reduce dose, switch to atypical, add anticholinergic. Levodopa is avoided — it worsens psychosis |
| Tardive dyskinesia | Months to years | Involuntary choreoathetoid movements — orofacial: lip smacking, chewing, tongue protrusion; may be irreversible | Stop or reduce the offending drug; switch to clozapine; VMAT2 inhibitors (valbenazine, tetrabenazine) |
Acute Dystonia — the Examination Focus
Presentation: occurs in the first few days of treatment, or after a dose increase or a single dose of an antiemetic such as metoclopramide or prochlorperazine. Risk is highest in young males.
Manifestations: oculogyric crisis (forced sustained upward deviation of the eyes), torticollis or retrocollis, jaw spasm (trismus), tongue protrusion, dysphagia and dysarthria, opisthotonus, and — rarely but dangerously — laryngeal dystonia causing stridor and airway compromise.
The reaction is frightening and often misdiagnosed as a seizure, tetanus, hysteria or a conversion reaction. The key is the drug history, and the fact that the patient is fully conscious throughout.
Treatment:
- parenteral anticholinergic — promethazine, benztropine or trihexyphenidyl — with dramatic relief within minutes
- a benzodiazepine may be added. Secure the airway if there is laryngeal involvement. Continue the anticholinergic orally for a few days, then reduce the antipsychotic dose or switch to a lower-potency or atypical agent.
Neuroleptic Malignant Syndrome
A rare, life-threatening idiosyncratic reaction to dopamine antagonists (or to abrupt withdrawal of dopaminergic drugs in Parkinson's disease).
Tetrad: hyperthermia, "lead-pipe" muscular rigidity, altered consciousness, and autonomic instability (labile blood pressure, tachycardia, sweating).
Investigations: grossly raised creatine kinase, leucocytosis, raised transaminases, myoglobinuria, acute kidney injury.
Onset: over days to weeks, often after dose escalation.
Management:
- stop the antipsychotic immediately
- supportive care in ICU with cooling and vigorous hydration to prevent renal failure from rhabdomyolysis
- dantrolene for rigidity and bromocriptine or amantadine as dopamine agonists
- benzodiazepines for agitation. Mortality is around 10%.
NMS versus acute dystonia versus serotonin syndrome. Acute dystonia is a focal sustained spasm in an alert, afebrile patient and responds to anticholinergics within minutes. NMS is febrile, rigid, hyporeflexic with a very high CK, developing over days. Serotonin syndrome is febrile with clonus and hyperreflexia, developing over hours after a serotonergic drug. Confusing these is a common and costly error.
Other Antipsychotic Adverse Effects
- Metabolic syndrome — weight gain, dyslipidaemia and diabetes, most marked with olanzapine and clozapine, requiring baseline and periodic monitoring of weight, waist circumference, glucose and lipids.
- Hyperprolactinaemia with galactorrhoea, amenorrhoea, gynaecomastia and sexual dysfunction, most marked with risperidone and typical agents.
- QT prolongation, anticholinergic effects, postural hypotension, and lowered seizure threshold.
All questions in Psychiatry
- SN1Write a short note on antidepressants — classes, mechanism, adverse effects and serotonin syndrome.
- SN2Write a short note on nicotine dependence and smoking cessation (de-addiction).
- SN3Discuss the aetiology, clinical features, diagnosis and management of depression.
- SN4Write a short note on obsessive-compulsive disorder.
- SN5Write a short note on bipolar disorder, including lithium therapy and its monitoring.
- SN6Write a short note on anxiety disorders.
- SN7Discuss the aetiology, clinical features, diagnosis and management of schizophrenia.
- SN8Write a short note on delirium and its differentiation from dementia.
- SN9Write a short note on anorexia nervosa and bulimia nervosa.
- SN10Write a short note on withdrawal syndromes.
- SN11Write a short note on somatoform disorders.
- SN12Write a short note on antipsychotic-induced extrapyramidal side effects, including acute dystonia.
- SN13Write a short note on alcohol misuse and its neuropsychiatric manifestations.