Citalopram × Lithium

Lithium enhances serotonergic transmission, and its SmPC names SSRIs among the drugs that can bring on serotonin syndrome. The second layer is cardiac: the same label advises avoiding lithium in patients already taking QT-prolonging drugs, while the citalopram label files such combinations under contraindications.

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia, sweating, diarrhoea, tachycardia, and in severe cases hyperthermia and rigidity. Symptoms usually appear within a day of adding the second drug or raising the dose. In patients with cardiac risk factors QTc is tracked separately.

Lithium is added to an antidepressant on purpose in treatment-resistant depression, and the NICE guideline includes this strategy. So the combination is not forbidden, but it needs monitoring. Before lithium is started, renal, cardiac and thyroid function are assessed (lithium label), and potassium and magnesium are corrected before citalopram is started (citalopram label). Lithium levels are checked 1–2 times a week at the start of treatment until they are stable, then every 1–2 months (lithium label). An extra level is taken after vomiting, diarrhoea, dehydration or an infection, and after starting a diuretic, an ACE inhibitor, an angiotensin receptor blocker or an NSAID. In people with cardiovascular disease or high cardiovascular risk, NICE advises considering ECG monitoring. If signs of arrhythmia appear, such as palpitations, skipped beats or fainting, citalopram is stopped and an ECG is done (citalopram label).