Pharmacology
Central nervous system and psychiatry
Neurological and psychiatric medicines are grouped here by the transmitter system they act on, because that is what predicts their adverse effects, their interactions and their withdrawal behaviour. Two drugs used for the same diagnosis often behave nothing alike, while a single drug frequently spans epilepsy, mood and pain because one mechanism serves all three.
13 classes across 6 mechanism families.
1. Anticonvulsant and membrane-stabilising agents
These medicines reduce pathological neuronal firing by acting on voltage-gated sodium or calcium channels, by enhancing GABAergic inhibition, or by binding synaptic vesicle protein 2A. The same mechanisms underlie their use in epilepsy, in mood stabilisation and in neuropathic pain.
- Antiepileptics — Reduce pathological neuronal firing by several distinct mechanisms; enzyme induction and teratogenicity dominate the safety picture.
- Mood stabilisers — Lithium and the anticonvulsant mood stabilisers; narrow therapeutic index and monitoring are the examinable points.
2. Monoamine-modulating antidepressants
These medicines raise synaptic serotonin, noradrenaline or both, most often by blocking reuptake. Their classes are separated far more by receptor selectivity and adverse-effect burden than by antidepressant efficacy.
- SSRI antidepressants — Selective serotonin reuptake inhibitors; hyponatraemia, bleeding risk and discontinuation symptoms are the class concerns.
- SNRIs and other antidepressants — Serotonin–noradrenaline reuptake inhibitors and the atypical agents that fit no other class.
- Tricyclic antidepressants — Older non-selective agents; antimuscarinic burden and cardiotoxicity in overdose are why they are second-line.
3. GABAergic and sedative agents
These medicines enhance inhibitory transmission at the GABA-A receptor, producing anxiolysis, sedation, hypnosis and anticonvulsant activity. Tolerance, dependence and withdrawal are class properties rather than agent-specific surprises.
- Benzodiazepines — GABA-A positive allosteric modulators; duration of action, dependence and flumazenil are the high-yield points.
- Z-drugs and other hypnotics — Non-benzodiazepine hypnotics and newer agents used for insomnia, with a similar dependence caution.
4. Dopamine receptor agents
These medicines block or stimulate dopamine receptors, chiefly D2. Blockade underlies antipsychotic effect and extrapyramidal adverse effects; stimulation underlies antiparkinsonian effect and its own impulse-control and psychiatric risks.
- Atypical antipsychotics — Second-generation agents with lower extrapyramidal risk but substantial metabolic effects; clozapine is monitored separately.
- Typical antipsychotics — First-generation D2 antagonists; extrapyramidal effects and tardive dyskinesia define their profile.
- Antiparkinsonian agents — Levodopa and the dopaminergic agents around it; wearing-off and impulse-control effects are examinable.
5. Headache and neurovascular agents
These medicines act on cranial vascular tone and trigeminal nociception, principally through serotonin 5-HT1B/1D receptors or the calcitonin gene-related peptide pathway, and are separated into acute and preventive roles.
- Triptans and migraine agents — 5-HT1B/1D agonists for acute attacks alongside the preventive agents; cardiovascular contraindications matter.
6. CNS stimulant and cognitive agents
These medicines increase catecholaminergic or cholinergic transmission to improve attention, wakefulness or cognitive symptoms. They span controlled stimulants and the symptomatic agents used in dementia.
- CNS stimulants and ADHD agents — Controlled stimulants and the non-stimulant alternatives; cardiovascular and growth monitoring are required.
- Dementia agents — Cholinesterase inhibitors and memantine; symptomatic benefit only, with a modest effect size.
Studying this the efficient way
Learn the mechanism family first, then the classes inside it. Almost every exam question about spectrum, adverse effects or resistance is really a question about which mechanism a drug belongs to. Each class page ends with a 60-second revision block and the traps students most often fall for.