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Mental Health Nursing · Chapter 5

The Synapse and the Two Clocks

Almost every psychiatric drug acts at one of five points on a synapse — and every one of them runs on two clocks at once: chemistry that changes within hours, and a brain that changes over weeks. Click each site to see what it costs and what it buys, then trace ten bedside findings back to the transmitter that explains them.

Five places a drug can act

Presynaptic terminal Synaptic cleft Postsynaptic neuron nucleus transporter enzyme

Trace the finding to its transmitter

0 of 10 traced

What is happening here

Choose a site, or trace a findingEvery site below is explained on both clocks — what the person feels within hours, and what the brain does over weeks. The gap between those two answers is the whole teaching problem of psychopharmacology, and it is why people stop a medication in week two.

The two clocks, side by side

Pharmacokinetic time · hours to daysTransporters block, receptors occupy, enzymes stop. The person feels nausea, jitteriness, sedation, a dry mouth, a stiff neck. Side effects arrive first.
Neuroplastic time · two to six weeksReceptors down-regulate, intracellular signalling shifts, brain-derived neurotrophic factor rises, new synapses grow. Benefit arrives later.
SSRI — nausea and jitteriness on day 1; sleep and appetite in week 1 to 2, energy next, mood at 2 to 6 weeks.
Antipsychotic — sedation and acute dystonia within hours; hallucinations and delusions settle over 1 to 3 weeks; tardive dyskinesia at months to years.
Benzodiazepine — relief within minutes; tolerance, dependence and cognitive dulling over weeks — the reason it is a bridge, not a destination.
Buspirone — nothing at all on day 1; 2 to 4 weeks to work — tell the person, or they will discard it in week one as useless.
Lithium — fine tremor, thirst and increased urination early; mood stabilisation over weeks, and its anti-suicide effect over the long run.
Esketamine — dissociation and raised blood pressure within the monitored 2 hours; the exception: relief of suicidal thoughts within hours, through glutamate.
Sort every finding by its time of onset first. Something that appeared within hours of a dose is almost always pharmacology. Something that appeared at three or four weeks is almost always the therapeutic effect arriving. A new movement at six months is almost always tardive. That single habit will get you to the right answer faster than memorising any list.