Major
Hydrochlorothiazide × Lithium
Thiazide diuretics×Psycholeptics. Lithium
Mechanism
Thiazide diuretics enhance lithium reabsorption in the proximal tubules via subclinical volume depletion. Serum lithium rises by 25–40% over 1–2 weeks.
Symptoms
Tremor, muscle twitching, nausea, diarrhoea, confusion, ataxia. Severe cases include seizures, coma, and nephrogenic diabetes insipidus with dehydration. Symptoms emerge when serum lithium exceeds 1.2 mmol/L.
Management
Reduce lithium dose by 25–30% when starting hydrochlorothiazide; check serum lithium at 1 week, then monthly. Alternative antihypertensive in bipolar patients: a calcium channel blocker (amlodipine), which does not affect lithium.