Psychopharmacology and Somatic Treatments
What this domain tests
This domain tests receptor profiles, adverse effects and their management, monitoring requirements, interactions and the indications for somatic treatments. Doses and monitoring schedules are fair game.
Core rules and concepts
- Antipsychotics: extrapyramidal effects (acute dystonia, akathisia, parkinsonism, tardive dyskinesia), hyperprolactinaemia, metabolic syndrome, QT prolongation. High-potency agents cause more extrapyramidal effects; low-potency agents cause more sedation and anticholinergic load.
- Antidepressants: SSRIs cause gastrointestinal upset, sexual dysfunction and hyponatraemia; TCAs are dangerous in overdose and anticholinergic; MAOIs risk hypertensive crisis with tyramine. Never combine serotonergic drugs without warning about serotonin syndrome.
- Mood stabilisers: lithium needs level, renal and thyroid monitoring; valproate is teratogenic; lamotrigine requires slow titration because of Stevens–Johnson syndrome, with a lower starting dose when valproate is co-prescribed; carbamazepine induces cytochrome enzymes.
- Pharmacokinetics: CYP2D6, CYP3A4 and CYP1A2 explain most interactions; smoking induces CYP1A2, grapefruit inhibits CYP3A4.
- Somatic treatments: ECT for severe, psychotic, catatonic or treatment-resistant illness, with transient memory impairment; rTMS for depression; ketamine and esketamine for resistant depression.
Worked example
A patient on fluoxetine is started on tramadol and develops agitation, tremor, clonus and fever. This is serotonin syndrome. Stop the serotonergic agents, give supportive care and consider cyproheptadine in moderate to severe cases.
Traps that cost marks
- Omitting the lithium level sampling time.
- Titrating lamotrigine quickly or ignoring the valproate interaction.
- Prescribing two serotonergic drugs and not warning the patient.