Antipsychotics and movement disorders
Antipsychotics split into first-generation agents, which strongly block dopamine and therefore cause more movement side effects, and second-generation agents, which cause fewer movement effects but carry substantial metabolic risk including weight gain, hyperglycaemia and dyslipidaemia. Metabolic monitoring — weight, glucose and lipids — is the recurring answer for second-generation agents.
Extrapyramidal symptoms come in four recognisable forms. Acute dystonia produces sudden muscle spasms, often of the neck, jaw or eyes, and can compromise the airway if the larynx is involved; it is treated urgently with an anticholinergic such as benztropine or diphenhydramine. Akathisia is intense motor restlessness and an inability to sit still, frequently misread as anxiety or worsening psychosis. Pseudoparkinsonism produces tremor, rigidity, shuffling gait and masked facies. Tardive dyskinesia produces involuntary repetitive movements of the face, tongue and limbs and may be irreversible, making early recognition and reporting essential.
Neuroleptic malignant syndrome is the emergency you must never miss. The picture is high fever, severe muscle rigidity described as lead-pipe, altered level of consciousness and autonomic instability with unstable blood pressure and tachycardia. The action is to stop the antipsychotic, notify the provider immediately, initiate cooling measures and support the airway and circulation. Mortality is significant when it is recognised late.
- •Acute dystonia: urgent, treat with benztropine or diphenhydramine
- •Akathisia: restlessness that is often mistaken for anxiety
- •Tardive dyskinesia: may be permanent — report early
- •NMS: fever, rigidity, altered consciousness — stop the drug, emergency care
Antidepressants and serotonin syndrome
Selective serotonin reuptake inhibitors are first-line and generally well tolerated, but three teaching points recur. First, therapeutic effect takes two to six weeks, so a client reporting no improvement after five days needs education rather than a medication change. Second, do not stop abruptly, because discontinuation symptoms occur. Third, and most importantly, suicide risk can increase in the early weeks as energy and initiative return before mood improves, so close monitoring during that window is essential.
Serotonin syndrome results from excessive serotonergic activity, most often when an SSRI is combined with another serotonergic agent such as an MAOI, triptan, tramadol or St John's wort. It presents with agitation and confusion, hyperreflexia and clonus, tremor, diaphoresis, diarrhoea and hyperthermia. Stop the serotonergic agents, notify the provider and provide supportive care. Distinguish it from NMS: serotonin syndrome features hyperreflexia and rapid onset, while NMS features lead-pipe rigidity and develops more slowly.
Older classes still appear. Tricyclic antidepressants carry anticholinergic effects, orthostatic hypotension and lethal cardiotoxicity in overdose, which matters in clients with suicidal ideation. MAOIs require strict avoidance of tyramine-rich foods such as aged cheese, cured meats, fermented products, draught beer and soy sauce, because a hypertensive crisis presenting with severe occipital headache can result.
| Syndrome | Trigger | Key findings | Immediate action |
|---|---|---|---|
| Neuroleptic malignant syndrome | Antipsychotics | Fever, lead-pipe rigidity, altered consciousness | Stop drug, cool, notify provider urgently |
| Serotonin syndrome | Combined serotonergic drugs | Hyperreflexia, clonus, agitation, diaphoresis, fever | Stop serotonergic agents, supportive care |
| Lithium toxicity | Dehydration, low sodium, NSAIDs, diuretics | Vomiting, diarrhoea, coarse tremor, ataxia, confusion | Hold dose, check level, notify provider |
| Hypertensive crisis | MAOI plus tyramine | Severe occipital headache, hypertension, palpitations | Emergency care, hold MAOI |
| Acute dystonia | Antipsychotics | Sudden neck, jaw or eye spasm | Benztropine or diphenhydramine, protect airway |
Mood stabilisers and anxiolytics
Lithium has one of the narrowest therapeutic ranges on the exam, at 0.6 to 1.2 mEq/L for maintenance. Early toxicity produces nausea, vomiting, diarrhoea, a coarse tremor replacing the usual fine tremor, and drowsiness. Progressive toxicity adds ataxia, confusion, slurred speech, and eventually seizures and cardiovascular collapse.
Because lithium is handled by the kidney alongside sodium, anything that reduces sodium or fluid raises the lithium level. Teach consistent daily salt and fluid intake of roughly two to three litres, caution around heavy exercise, hot weather, vomiting and diarrhoea, and avoidance of NSAIDs and certain diuretics without provider advice. Regular level monitoring plus thyroid and renal function testing is standard.
Benzodiazepines relieve acute anxiety quickly but cause sedation, fall risk in older adults, and dependence with prolonged use. Never combine with alcohol or other central nervous system depressants. Flumazenil is the reversal agent. Buspirone, by contrast, is non-sedating and non-addictive but takes weeks to work, so it is inappropriate for acute panic — a distinction the exam tests directly.
- •Lithium maintenance range 0.6–1.2 mEq/L; coarse tremor signals toxicity
- •Consistent sodium and 2–3 litres of fluid daily protect against toxicity
- •Benzodiazepines: fall risk, dependence, never with alcohol
- •Buspirone is not for acute anxiety — it takes weeks
How to revise psych pharmacology
Learn the emergencies first, because they generate the highest-stakes and most frequent items. If you can distinguish neuroleptic malignant syndrome, serotonin syndrome, lithium toxicity and hypertensive crisis on presentation alone, you have covered a large proportion of the psychiatric pharmacology content on the exam.
Then layer the teaching points, which cluster into onset timing, food and drug interactions, monitoring parameters and abrupt-discontinuation warnings. These are the raw material for the 'which client statement indicates understanding' item type that mental health sections use heavily.
Finally, practise them inside mental health question sets alongside therapeutic communication items, because the exam interleaves them and switching between response-selection logic and pharmacology logic is a skill in itself.