Hydrochlorothiazide

Hydrochlorothiazide (HCTZ or HCT) is a thiazide diuretic — a type of water tablet — used primarily to lower blood pressure and reduce excess fluid in the body. It works by causing the kidneys to excrete more sodium and water, which lowers blood volume and therefore blood pressure. Hydrochlorothiazide is one of the most widely prescribed antihypertensives in Nigeria and is often used in combination with other blood pressure medications. It is inexpensive, effective, and available at most government and private health facilities. Thiazide diuretics are particularly effective in patients of African descent with hypertension.

• Hypertension (high blood pressure) — often as part of combination therapy • Oedema (fluid retention) — from heart failure, liver cirrhosis, or kidney disease • Prevention of kidney stones in people who form calcium oxalate stones • Nephrogenic diabetes insipidus (a rare kidney condition)

Hypertension: • Typical dose: 12.5–25 mg once daily in the morning • Maximum dose: 50 mg daily Oedema: • 25–100 mg daily, adjusted based on response Take in the morning — this prevents the need to urinate frequently at night. Take with or without food. Do not skip doses or stop without consulting your doctor. Expect increased urination, especially in the first few weeks — this is the intended effect of the drug. The diuretic (water-loss) effect is greatest initially and tends to decrease with continued use while the blood-pressure-lowering effect persists.

Common: • Increased urination (diuresis) — particularly in the first few weeks • Dizziness or lightheadedness, especially when standing quickly (postural hypotension) • Thirst • Muscle cramps (from electrolyte loss) • Fatigue • Headache Electrolyte imbalances (important — check with blood tests): • Hypokalaemia (low potassium) — muscle weakness, cramps, palpitations, irregular heartbeat; eat potassium-rich foods (banana, plantain, beans, orange) or take potassium supplement as advised • Hyponatraemia (low sodium) — nausea, headache, confusion • Hypomagnesaemia (low magnesium) Other effects: • Raised uric acid (can trigger gout attacks) • Raised blood glucose (thiazides modestly worsen glycaemic control) • Increased cholesterol and triglycerides • Sun sensitivity (photosensitivity) — use sunscreen • Impotence (erectile dysfunction) in some men

• ACE inhibitors and ARBs (e.g., lisinopril, losartan): combination is common in hypertension treatment; monitor potassium and kidney function; first-dose hypotension risk • Lithium: thiazides increase lithium levels significantly — risk of lithium toxicity • NSAIDs (ibuprofen, diclofenac): reduce diuretic and antihypertensive effect; increase risk of kidney problems • Digoxin: hypokalaemia from HCTZ increases digoxin toxicity risk — maintain potassium in normal range • Antidiabetic drugs: HCTZ raises blood glucose, potentially requiring dose adjustments • Corticosteroids: increase potassium loss • Amiodarone, some antiarrhythmics: hypokalaemia increases arrhythmia risk • Alcohol: enhanced blood pressure lowering

• Store at room temperature (below 25°C) away from moisture, heat, and sunlight • Keep in original container; keep out of reach of children