Antidepressants and serotonin syndrome flashcards
22 high-yield MRCP Part 1 cards from the Intellect Medicos Psychiatry course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
Study these 22 cards Save progress — free account
-
Which SSRI is preferred in a patient with depression after a recent myocardial infarction?
Show answer
Sertraline.
Why? Sertraline has the best evidence of cardiac safety after MI and is the usual first-line SSRI.
-
Which two SSRIs carry a dose-related risk of QT prolongation?
Show answer
Citalopram and escitalopram.
Why? Both prolong the QT interval in a dose-dependent way, so avoid them with other QT-prolonging drugs or known long QT.
-
An 82-year-old woman started sertraline 3 weeks ago. She is now confused. She is clinically euvolaemic, serum sodium 119 mmol/L, with inappropriately concentrated urine. What is the most likely cause of her hyponatraemia?
Show answer
SIADH caused by the SSRI.
Why? SSRIs can cause SIADH, especially in older people, women, low body weight and those on diuretics. Check sodium in at-risk patients after starting.
-
A patient on an SSRI also needs a regular NSAID. What should be co-prescribed?
Show answer
A proton pump inhibitor (gastroprotection).
Why? SSRIs impair platelet aggregation (platelets rely on serotonin uptake), and with an NSAID the risk of GI bleeding is much higher.
-
Which antidepressant is preferred for a patient taking warfarin or a DOAC?
Show answer
Mirtazapine.
Why? SSRIs add to bleeding risk with anticoagulants. Mirtazapine works by blocking presynaptic alpha-2 receptors and has much less effect on platelets.
-
When should a 21-year-old starting an antidepressant for depression first be reviewed?
Show answer
After 1 week.
Why? People aged 18–25 have a higher risk of suicidal thoughts and agitation early in treatment, as does anyone with particular suicide concern. Most other adults are reviewed within about 2 weeks.
-
Which examination findings point to serotonin syndrome rather than neuroleptic malignant syndrome?
Show answer
Hyperreflexia and clonus (often inducible or ocular, worse in the legs), with dilated pupils and rapid onset over hours.
Why? NMS instead gives 'lead-pipe' rigidity with slowed reflexes, developing over days.
-
What is the first-line management of serotonin syndrome?
Show answer
Stop all serotonergic drugs, give supportive care (IV fluids, cooling) and benzodiazepines for agitation; consider cyproheptadine if severe.
Why? Most cases settle within 24–72 hours once the drugs are stopped. Cyproheptadine is a 5-HT2A antagonist.
-
A 30-year-old has taken an overdose of amitriptyline. She is drowsy with dilated pupils, a dry mouth and HR 130. ECG shows QRS duration 140 ms. What is the first-line specific treatment?
Show answer
IV sodium bicarbonate.
Why? The sodium load and alkalinisation overcome the sodium-channel blockade that widens the QRS and causes arrhythmias.
-
A man taking phenelzine for depression eats a large amount of mature cheese and cured meat. An hour later he has a severe occipital headache and BP 230/130. What is the mechanism of this reaction?
Show answer
MAO inhibition stops tyramine being broken down in the gut and liver; tyramine then releases noradrenaline, causing a hypertensive crisis.
Why? This is the 'cheese reaction'. Patients on MAOIs must avoid tyramine-rich foods (aged cheese, cured meats, yeast extracts, some wines) and sympathomimetic drugs.
-
What is the mechanism of action of SSRIs?
Show answer
They block the serotonin transporter (SERT), reducing reuptake of 5-HT into the presynaptic neuron and raising synaptic serotonin.
Why? The rise in serotonin is immediate, but mood benefit takes 2–4 weeks as receptors adapt.
-
The SSRI with the worst discontinuation symptoms is ______; the one with the fewest, because of its long half-life, is fluoxetine.
Show answer
paroxetine
Why? Paroxetine has a short half-life and more anticholinergic effects. Discontinuation symptoms include GI upset, mood swings, restlessness, paraesthesia, poor sleep and sweating.
-
The SSRI with the worst discontinuation symptoms is paroxetine; the one with the fewest, because of its long half-life, is ______.
Show answer
fluoxetine
Why? Paroxetine has a short half-life and more anticholinergic effects. Discontinuation symptoms include GI upset, mood swings, restlessness, paraesthesia, poor sleep and sweating.
-
If an antidepressant is needed for a child or young person with moderate–severe depression, which is first line?
Show answer
Fluoxetine (alongside psychological therapy).
Why? Fluoxetine has the best evidence of benefit in under-18s. Monitor closely for suicidal thoughts and agitation early in treatment.
-
Which antibiotic can cause serotonin syndrome when given with an SSRI?
Show answer
Linezolid.
Why? Linezolid is a weak, reversible monoamine oxidase inhibitor, so it adds to serotonergic effects.
-
Which dose-related cardiovascular side effect of venlafaxine needs regular monitoring?
Show answer
Hypertension.
Why? SNRIs inhibit noradrenaline as well as serotonin reuptake, raising blood pressure and heart rate. The most common side effects are still GI.
-
What is the mechanism of action of tricyclic antidepressants?
Show answer
They inhibit reuptake of noradrenaline and serotonin.
Why? They also block muscarinic, histamine H1 and alpha-1 receptors (dry mouth, sedation, postural hypotension) and cardiac sodium channels (QRS widening and arrhythmias in overdose).
-
Which ECG changes are typical of tricyclic antidepressant overdose?
Show answer
Sinus tachycardia with a widened QRS and a prolonged QT interval.
Why? QRS widening reflects sodium-channel blockade and predicts seizures and ventricular arrhythmias. A QRS over 100 ms is an indication for IV sodium bicarbonate.
-
What is the mechanism of action of mirtazapine?
Show answer
It blocks presynaptic alpha-2 adrenoceptors, increasing release of noradrenaline and serotonin (a NaSSA). It also blocks 5-HT2 and 5-HT3 receptors.
Why? This gives sedation and increased appetite with little sexual dysfunction, which suits patients with poor sleep and weight loss.
-
Why does NICE advise against prescribing or recommending St John's wort for depression?
Show answer
Preparations vary in strength, the right dose is uncertain, and it has serious drug interactions because it induces liver enzymes (CYP3A4).
Why? It reduces levels of drugs such as the combined pill, warfarin and anticonvulsants, and adds to serotonin syndrome risk with SSRIs.
-
Among tricyclic antidepressants, ______ is the least toxic in overdose.
Show answer
lofepramine
Why? Dosulepin and amitriptyline are the most dangerous in overdose, so avoid TCAs in patients at risk of suicide.
-
Which persistent adverse effect, which can continue after the drug is stopped, did the MHRA in October 2026 require antidepressant leaflets to name?
Show answer
Sexual dysfunction (post-SSRI sexual dysfunction, PSSD).
Why? Prescribers should discuss it, and the risk of suicidal thoughts, when starting or changing the dose. It applies to SSRIs, SNRIs and some tricyclics (e.g. amitriptyline).