VALSARTAN AND 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 inhibits the binding of angiotensin II to the AT1 receptor, thereby antagonizing angiotensin II-induced vasoconstriction, aldosterone secretion, and renal sodium reabsorption. Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing sodium and water reabsorption.
| Metabolism | Valsartan is minimally metabolized (approximately 20%) via CYP2C9 to an inactive metabolite; the majority is excreted unchanged in bile and urine. Hydrochlorothiazide is not metabolized significantly and is excreted unchanged by the kidneys. |
| Excretion | Valsartan: 83% eliminated via feces (biliary), 13% via urine; Hydrochlorothiazide: ≥95% eliminated unchanged via urine. |
| Half-life | Valsartan: Terminal half-life ~6 hours; Hydrochlorothiazide: Terminal half-life ~6-15 hours (prolonged in renal impairment). |
| Protein binding | Valsartan: 94-97% bound to serum albumin; Hydrochlorothiazide: 40-68% bound to serum albumin. |
| Volume of Distribution | Valsartan: Vd ~17 L (0.24 L/kg); Hydrochlorothiazide: Vd ~3-4 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Valsartan: Oral bioavailability ~25% (range 10-35%); Hydrochlorothiazide: Oral bioavailability ~65-70%. |
| Onset of Action | Oral: Valsartan and Hydrochlorothiazide combination: Antihypertensive effect begins within 2 hours, peak effect at 4-6 hours. |
| Duration of Action | Oral: Antihypertensive effect persists for 24 hours; duration of diuretic effect of hydrochlorothiazide is 6-12 hours. |
| Molecular Weight | 435.52 Da (valsartan), 297.74 Da (hydrochlorothiazide) |
Oral, one tablet once daily. Starting dose: 160/12.5 mg or 80/12.5 mg. Titrate to 160/25 mg or 320/12.5 mg-320/25 mg based on response. Max: 320/25 mg/day.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR <30 mL/min/1.73m2. For GFR 30-60 mL/min/1.73m2: no dose adjustment needed; monitor renal function and electrolytes. Total daily dose of hydrochlorothiazide should not exceed 25 mg. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Maximum valsartan 80 mg/day; monitor. Child-Pugh C: Contraindicated due to hydrochlorothiazide. Valsartan: caution, no specific dose recommendations; avoid if severe hepatic impairment. |
| Pediatric use | Safety and efficacy not established in pediatric patients (<18 years). Not recommended. |
| Geriatric use | Initiate at lower dose (e.g., 80/12.5 mg) due to risk of renal impairment and electrolyte disturbances. Monitor blood pressure, renal function, and serum electrolytes closely. Avoid use if GFR <30 mL/min/1.73m2. |
| 1st trimester | Avoid, risk of teratogenicity associated with ARBs and thiazide diuretics. |
| 2nd trimester | Contraindicated, fetal renal impairment and oligohydramnios risk. |
| 3rd trimester | Contraindicated, fetal renal dysfunction and neonatal toxicity. |
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 detected in fetal plasma, hydrochlorothiazide crosses readily. |
| Breastfeeding | Avoid due to secretion in breast milk and potential adverse effects on the nursing infant. |
■ FDA Black Box Warning
Fetal toxicity: Use during pregnancy can cause injury and death to the developing fetus. Discontinue as soon as pregnancy is detected.
| Common Effects | heart failure |
| Serious Effects |
Pregnancy (especially 2nd and 3rd trimesters)AnuriaHypersensitivity to valsartan, hydrochlorothiazide, or sulfonamide-derived drugs
| Precautions | Avoid use in pregnancy and breastfeeding, Monitor renal function and electrolytes (especially potassium, sodium, and magnesium), Hypotension and syncope may occur, especially in volume-depleted patients, May worsen renal function in patients with renal artery stenosis or severe heart failure, Hydrochlorothiazide may cause acute angle-closure glaucoma or myopia (sulfonamide effect), Hyperuricemia and gout may occur with thiazide use, May increase serum lithium levels and toxicity |
| Food/Dietary |
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| Lactation Rating | L4 |
| Teratogenic Risk | First trimester: Potential for teratogenic effects from angiotensin receptor blocker (ARB) component; risk of fetal renal dysfunction, oligohydramnios, and skull ossification defects. Second and third trimesters: ARB exposure causes fetal renal hypoperfusion, oligohydramnios, anuria, renal failure, pulmonary hypoplasia, and death. Hydrochlorothiazide (HCTZ) is associated with fetal/neonatal jaundice, electrolyte disturbances, and thrombocytopenia. Both ARBs and HCTZ are contraindicated in the second and third trimesters. Risk Summary: ARBs are teratogenic and fetotoxic in all trimesters; HCTZ poses risks later in pregnancy. |
| Fetal Monitoring | Maternal: Blood pressure, serum creatinine, BUN, electrolytes (especially potassium, sodium, chloride, bicarbonate), uric acid, and urine output. Fetal: Ultrasound monitoring of amniotic fluid volume and fetal kidney function if ARB exposure after first trimester. Monitor for oligohydramnios and fetal growth restriction. Neonatal: Observe for hypotension, hyperkalemia, and renal dysfunction if exposure occurred in utero. |
| Fertility Effects | No definitive studies on fertility effects in humans. ARBs may theoretically affect reproductive function via renin-angiotensin system modulation, but clinical significance unknown. HCTZ has no known significant impact on fertility. Overall, no evidence of major fertility impairment. |
| Avoid high-potassium foods (e.g., bananas, oranges, spinach). Limit alcohol intake. Avoid excessive salt substitutes. Grapefruit juice may alter valsartan metabolism. |
| Clinical Pearls | Monitor serum potassium and creatinine within 2 weeks of initiation. Avoid in pregnancy (category D). Can cause acute angle-closure glaucoma due to sulfonamide component. Use with caution in renal artery stenosis. |
| Patient Advice | Take exactly as prescribed, usually once daily. · Avoid salt substitutes containing potassium. · Report symptoms of low blood pressure (dizziness, fainting). · May cause dizziness or lightheadedness; change positions slowly. · Do not take if pregnant or planning pregnancy. · May increase sensitivity to sunlight; use sunscreen. · Do not stop abruptly without consulting your doctor. |