VALSARTAN; HYDROCHLOROTHIAZIDE
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.
Valsartan is an angiotensin II receptor blocker (ARB) that selectively blocks the binding of angiotensin II to the AT1 receptor, leading to vasodilation and reduced aldosterone secretion. Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, increasing excretion of sodium and water.
| Metabolism | Valsartan is primarily metabolized by CYP2C9; minimal hepatic metabolism. Hydrochlorothiazide is not metabolized and is excreted unchanged in urine. |
| Excretion | Valsartan: primarily excreted unchanged in feces (70%) via biliary elimination, with renal excretion accounting for about 30% (mostly unchanged). Hydrochlorothiazide: eliminated by renal excretion, with approximately 95% of the absorbed dose excreted unchanged in urine via tubular secretion. |
| Half-life | Valsartan: terminal half-life is approximately 6 hours. Hydrochlorothiazide: terminal half-life ranges from 5.6 to 14.8 hours, with an average of about 8 hours; prolonged in renal impairment. |
| Protein binding | Valsartan: highly bound to serum proteins (94-97%), primarily albumin. Hydrochlorothiazide: approximately 40-68% bound to plasma proteins, mainly albumin. |
| Volume of Distribution | Valsartan: apparent volume of distribution is about 17 L (0.24 L/kg), indicating distribution into extracellular fluid. Hydrochlorothiazide: volume of distribution is approximately 0.8-1.2 L/kg, suggesting distribution into total body water. |
| Bioavailability | Valsartan: oral bioavailability is about 25% due to extensive first-pass metabolism. Hydrochlorothiazide: oral bioavailability is 60-80%, varying with formulation. |
| Onset of Action | Valsartan: peak plasma concentrations occur 2-4 hours after oral administration; antihypertensive effect begins within 2 hours. Hydrochlorothiazide: diuretic effect begins within 2 hours, peak effect at 4-6 hours; antihypertensive effect may take 3-4 days. |
| Duration of Action | Valsartan: antihypertensive effect lasts for about 24 hours, allowing once-daily dosing. Hydrochlorothiazide: diuretic effect persists for 6-12 hours; antihypertensive effect with chronic dosing lasts 24 hours. |
| Molecular Weight | Valsartan: 435.5 Da; Hydrochlorothiazide: 297.74 Da |
80-320 mg valsartan / 12.5-25 mg hydrochlorothiazide once daily orally, titrated based on blood pressure response.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR <30 mL/min/1.73m². For GFR 30-60 mL/min/1.73m², maximum dose 160/25 mg once daily. Monitor electrolytes and renal function. |
| Liver impairment | For mild-to-moderate hepatic impairment (Child-Pugh A or B): maximum valsartan dose 80 mg once daily; no adjustment for hydrochlorothiazide. Contraindicated in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Safety and efficacy not established in children <18 years. Not recommended. |
| Geriatric use | Start at lowest dose (80/12.5 mg once daily) with careful monitoring of blood pressure, electrolytes, and renal function due to age-related changes. |
| 1st trimester | Contraindicated due to risk of oligohydramnios, fetal renal dysfunction, and skeletal malformations. |
| 2nd trimester | Contraindicated; exposure in second and third trimesters is associated with fetal hypotension, anuria, and irreversible renal injury. |
| 3rd trimester | Contraindicated; use during third trimester increases risk of neonatal hypotension, renal failure, skull hypoplasia, and oligohydramnios. |
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 components cross the placenta. Valsartan is actively transferred to fetal circulation; hydrochlorothiazide crosses readily and may cause fetal electrolyte disturbances. |
■ 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 pregnancy is detected.
| Common Effects | heart failure |
| Serious Effects |
AnuriaHypersensitivity to sulfonamide-derived drugs (hydrochlorothiazide)History of angioedema with ACE inhibitors or ARBsSevere renal impairment (CrCl <30 mL/min)Pregnancy (especially second and third trimesters)
| Precautions | Hypotension, renal impairment, hyperkalemia, electrolyte imbalances (hypokalemia, hyponatremia, hypomagnesemia), acute angle-closure glaucoma, exacerbation of systemic lupus erythematosus, fetal/neonatal morbidity, anaphylactic reactions, angioedema |
| Food/Dietary | Avoid high-potassium foods (e.g., bananas, oranges, spinach, avocados) in excess unless monitored. Avoid salt substitutes containing potassium. Limit alcohol intake. Maintain adequate fluid intake to prevent dehydration; avoid excessive fluid restriction. |
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| Breastfeeding |
| Both valsartan and hydrochlorothiazide are excreted into human milk. Valsartan levels are low but hydrochlorothiazide may suppress lactation and cause neonatal electrolyte disturbances. Use only if clearly needed and monitor infant for dehydration, electrolyte imbalance, and hypotension. |
| Lactation Rating | L3 (Moderately Safe) - Limited data; avoid in nursing mothers with infants who have electrolyte abnormalities or renal impairment. |
| Teratogenic Risk | First trimester: Risk of teratogenicity limited but potential for fetotoxicity increases with exposure. Second and third trimesters: Exposure associated with fetal renal hypoperfusion, oligohydramnios, skull ossification defects, anuria, renal failure, hypotension, and death. Hydrochlorothiazide may cause fetal jaundice, electrolyte disturbances. |
| Fetal Monitoring | Monitor maternal blood pressure, renal function (serum creatinine, BUN), electrolytes, and urine output. Fetal ultrasonography to assess amniotic fluid index, fetal growth, and renal anatomy. Monitor for oligohydramnios and fetal distress. |
| Fertility Effects | Data insufficient. Animal studies with valsartan showed no adverse effects on fertility. Hydrochlorothiazide has no known direct effect on fertility. However, the combination may theoretically affect reproductive function through hemodynamic changes. |
| Clinical Pearls | Monitor serum potassium closely due to valsartan's potassium-retaining effect and hydrochlorothiazide's potassium-wasting effect; net effect may be neutral but requires regular monitoring. Assess renal function and electrolytes before initiation and periodically thereafter. Avoid in pregnancy (angiotensin receptor blocker risk) and breastfeeding (hydrochlorothiazide may suppress lactation). Avoid concomitant use with aliskiren in patients with diabetes or renal impairment (eGFR <60 mL/min). Use with caution in patients with gout or hyperuricemia due to hydrochlorothiazide. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. · Do not stop taking this medication without consulting your doctor. · Avoid becoming pregnant; use effective contraception while on this medication. · Report any signs of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat, excessive thirst. · Limit alcohol intake as it may lower blood pressure further. · Avoid potassium supplements and salt substitutes containing potassium without doctor approval. · Get up slowly from sitting or lying to prevent dizziness from low blood pressure. · Take the last dose of the day at least 4 hours before bedtime to avoid nighttime urination. · Store at room temperature away from moisture and heat. |