HYDROCHLOROTHIAZIDE; VALSARTAN
Clinical safety rating: avoid
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing sodium and water reabsorption. Valsartan is an angiotensin II receptor blocker (ARB) that selectively blocks the binding of angiotensin II to AT1 receptors, causing vasodilation and reduced aldosterone secretion.
| Metabolism | Hydrochlorothiazide is not metabolized and is excreted unchanged in urine. Valsartan is primarily metabolized by CYP2C9 to an inactive metabolite, with minor metabolism by CYP3A4. |
| Excretion | Hydrochlorothiazide: ~70% renal (unchanged) via tubular secretion; ~30% biliary/fecal. Valsartan: 83% fecal (unchanged); 13% renal (unchanged and metabolites). |
| Half-life | Hydrochlorothiazide: 6-15 hours (terminal); clinical effect persists due to tubular secretion. Valsartan: 6 hours (terminal); no accumulation with once-daily dosing. |
| Protein binding | Hydrochlorothiazide: 68% bound to albumin. Valsartan: 94-97% bound to albumin (primarily). |
| Volume of Distribution | Hydrochlorothiazide: 3-4 L/kg; extensive distribution into extracellular fluid. Valsartan: 0.17 L/kg; limited tissue distribution. |
| Bioavailability | Hydrochlorothiazide: oral, 65-75% (estimated). Valsartan: oral, 25% (variable, 10-35%) due to extensive first-pass metabolism. |
| Onset of Action | Hydrochlorothiazide: oral, 2 hours (diuresis); peak antihypertensive effect 4-6 hours. Valsartan: oral, 2 hours (antihypertensive); peak effect 4-6 hours. |
| Duration of Action | Hydrochlorothiazide: 12-16 hours (diuresis); 24 hours (antihypertensive) with chronic use. Valsartan: 24 hours (antihypertensive) with once-daily dosing. |
| Molecular Weight | Hydrochlorothiazide: 297.74 Da; Valsartan: 435.5 Da |
Oral, 12.5-25 mg hydrochlorothiazide / 80-320 mg valsartan once daily. Maximum dose: 25 mg hydrochlorothiazide / 320 mg valsartan per day.
| Dosage form | TABLET |
| Renal impairment | GFR ≥30 mL/min/1.73 m²: no adjustment. GFR 15-29 mL/min/1.73 m²: not recommended due to limited data; avoid use. GFR <15 mL/min/1.73 m²: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: caution; maximum dose 80 mg valsartan component. Child-Pugh C: contraindicated. |
| Pediatric use | Not approved for use in pediatric patients under 18 years of age. |
| Geriatric use | Start at lower end of dosing range (e.g., 12.5 mg hydrochlorothiazide / 80 mg valsartan) due to increased risk of hypotension and electrolyte disturbances; monitor renal function and electrolytes closely. |
| 1st trimester | Avoid in first trimester due to potential teratogenic effects; use only if no alternative. Fetal exposure may increase risk of congenital anomalies. |
| 2nd trimester | Contraindicated due to fetal oligohydramnios, renal dysfunction, and skull ossification defects. |
| 3rd trimester | Contraindicated due to fetal and neonatal hypotension, hyperkalemia, and renal impairment. |
Clinical note
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
| FDA category | Contraindicated |
| Placental transfer | Both drugs cross the placenta. Hydrochlorothiazide readily crosses; valsartan crosses in animal studies, likely in humans. Exposure can cause fetal harm. |
■ FDA Black Box Warning
Fetal toxicity: Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue as soon as possible once pregnancy is detected.
| Common Effects | heart failure |
| Serious Effects |
AnuriaHypersensitivity to hydrochlorothiazide or valsartanHistory of angioedema with ACE inhibitors or ARBsPregnancy (especially second and third trimesters)Concomitant use with aliskiren in patients with diabetes
| Precautions | Hypotension in volume-depleted patients, Electrolyte imbalances (hypokalemia, hyponatremia, hypomagnesemia), Renal function impairment, Acute angle-closure glaucoma (hydrochlorothiazide), Sulfonamide allergy cross-reactivity, Exacerbation of systemic lupus erythematosus, Metabolic effects (hyperglycemia, hyperuricemia) |
| Food/Dietary |
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| Breastfeeding |
| Hydrochlorothiazide passes into breast milk in small amounts; may reduce milk production. Valsartan is present in very low concentrations. Caution is advised; consider alternatives, especially in preterm infants. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category D. First trimester: Potential fetotoxicity, but limited data. Second and third trimesters: Fetal hypotension, oligohydramnios, renal dysfunction, skull ossification defects, and neonatal anuria or hyperkalemia. ARBs cause fetotoxicity in second and third trimesters. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes, renal function, and urine output. Fetal ultrasound for oligohydramnios, fetal growth, and renal function. Neonates exposed in utero should be observed for hypotension, hyperkalemia, and oliguria. |
| Fertility Effects | No significant adverse effects on fertility reported in animal studies or human data. Hydrochlorothiazide does not impair fertility. Valsartan has no known effects on fertility. |
| Avoid high-potassium foods (bananas, oranges, spinach, potatoes) in large amounts; may increase risk of hyperkalemia. Reduce sodium intake for optimal blood pressure control. Alcohol may potentiate hypotensive effects. |
| Clinical Pearls | Monitor serum potassium and creatinine within 1-2 weeks of initiation or dose adjustment, especially in elderly, renal impairment, or on NSAIDs. Valsartan's antihypertensive effect is additive with HCTZ; onset at 2-4 weeks. Use cautiously in gout patients due to HCTZ-induced hyperuricemia. Avoid in pregnancy (category D). |
| Patient Advice | Take exactly as prescribed, usually once daily; do not skip doses. · Avoid pregnancy; use effective contraception; stop drug immediately if pregnant. · May cause dizziness or lightheadedness; rise slowly from sitting/lying position. · Avoid potassium supplements or salt substitutes containing potassium unless directed. · Report symptoms of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat. · Limit alcohol intake as it may lower blood pressure further. · May take with or without food; taking with food may reduce stomach upset. · Do not use NSAIDs (e.g., ibuprofen) without consulting doctor as they may reduce effectiveness and worsen kidney function. |