AVALIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for AVALIDE (AVALIDE).
Avalide is a combination of an angiotensin II receptor blocker (irbesartan) and a thiazide diuretic (hydrochlorothiazide). Irbesartan blocks the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively antagonizing the AT1 receptor. Hydrochlorothiazide increases sodium and water excretion by inhibiting the Na+/Cl- symporter in the distal convoluted tubule.
| Metabolism | Irbesartan is metabolized primarily via glucuronidation (UGT1A1, UGT1A3, UGT2B7) and to a lesser extent via CYP2C9 oxidation. Hydrochlorothiazide is not extensively metabolized, with majority excreted unchanged in urine. |
| Excretion | Renal: HCTZ ~70% unchanged; Irbesartan ~20% unchanged, remainder as metabolites via biliary (60%) and renal (20%). Combined: Renal ~50%, biliary/fecal ~50%. |
| Half-life | Irbesartan: 11-15 h (terminal), HCTZ: 6-15 h (terminal). Clinical context: Steady state reached in 3-5 days; allows once-daily dosing. |
| Protein binding | Irbesartan: >90% bound (albumin and α1-acid glycoprotein); HCTZ: ~68% bound (albumin). |
| Volume of Distribution | Irbesartan: 53-93 L (0.7-1.2 L/kg); HCTZ: 3-15 L (0.04-0.2 L/kg). Clinical meaning: Irbesartan distributes extensively; HCTZ remains mostly in extracellular fluid. |
| Bioavailability | Irbesartan: ~60-80% oral; HCTZ: ~65-75% oral. Not affected by food. |
| Onset of Action | Irbesartan: 2-4 h after oral dose; HCTZ: 2 h after oral dose. Antihypertensive effect seen within 2 weeks. |
| Duration of Action | Irbesartan: >24 h for blood pressure lowering; HCTZ: 12-24 h for diuretic effect. Clinical note: Once-daily dosing effective for 24-h BP control. |
| Molecular Weight | 428.53 |
AVALIDE (irbesartan/hydrochlorothiazide) is available as tablets containing 150/12.5 mg, 300/12.5 mg, or 300/25 mg. The typical starting dose is 150/12.5 mg once daily, titrated to 300/12.5 mg once daily as needed. Maximum dose is 300/25 mg once daily.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in anuria and severe renal impairment (CrCl <30 mL/min). For CrCl 30-60 mL/min, initiate with 150/12.5 mg once daily, monitor closely. No adjustment for CrCl >60 mL/min. |
| Liver impairment | No specific guidelines for Child-Pugh classification. Use caution in severe hepatic impairment due to potential electrolyte disturbances. Consider lower doses if indicated. |
| Pediatric use | Not recommended for pediatric patients below 18 years of age. |
| Geriatric use | Start at lowest dose (150/12.5 mg) and titrate cautiously. Monitor renal function and electrolytes frequently. |
| 1st trimester | Use during first trimester is associated with a potential risk of fetal renal dysfunction and oligohydramnios. Avoid if possible. |
| 2nd trimester | Use during second trimester is contraindicated due to risk of fetal hypotension, anuria, and renal failure. Discontinue immediately if pregnancy detected. |
| 3rd trimester | Use during third trimester is contraindicated due to risk of severe fetal/neonatal adverse effects including oligohydramnios, skull hypoplasia, and neonatal renal failure. |
Clinical note
Comprehensive clinical and safety monograph for AVALIDE (AVALIDE).
| Placental transfer | Irbesartan crosses the placenta in animals and humans; hydrochlorothiazide also crosses the placenta. Both can affect fetal renal function and amniotic fluid volume. |
| Breastfeeding | Hydrochlorothiazide and irbesartan are excreted into human milk. Hydrochlorothiazide may suppress lactation. Irbesartan is present in low levels but effects on the nursing infant are unknown. Use with caution, especially in premature infants or those with renal impairment. |
■ FDA Black Box Warning
WARNING: FETAL TOXICITY - When pregnancy is detected, discontinue Avalide as soon as possible. Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus.
| Serious Effects |
PregnancyHypersensitivity to irbesartan, hydrochlorothiazide, or sulfonamide-derived drugsAnuriaConcomitant use with aliskiren in patients with diabetes
| Precautions | Fetal toxicity, Hypotension in volume-depleted patients, Impaired renal function, Electrolyte imbalances (hyperkalemia, hyponatremia, hypokalemia, hypomagnesemia), Acute angle-closure glaucoma (due to hydrochlorothiazide sulfonamide component), Exacerbation of systemic lupus erythematosus, Metabolic acidosis |
| Food/Dietary | Avoid excessive salt intake. Limit alcohol. Foods high in potassium (e.g., bananas, oranges, avocados) may increase risk of hyperkalemia; monitor intake. No significant interaction with grapefruit. |
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| Lactation Rating | L3 (Moderately Safe) - Limited data; potential for adverse effects in infant. |
| Teratogenic Risk | First trimester: Increased risk of congenital malformations (cardiovascular, CNS) associated with ARBs; second and third trimesters: Oligohydramnios, fetal renal dysfunction, skull ossification defects, hypotension, and anuria. Risk is highest in second and third trimesters. |
| Fetal Monitoring | Monitor maternal blood pressure, renal function, and serum potassium; fetal ultrasound for oligohydramnios, renal anomalies, and growth restriction. |
| Fertility Effects | No specific fertility studies, but ARBs may theoretically affect renin-angiotensin system in reproductive tissues; consider alternative antihypertensives in women planning pregnancy. |
| Clinical Pearls | Avalide is a fixed-dose combination of irbesartan (ARB) and hydrochlorothiazide (thiazide diuretic). Initiate only after failure of monotherapy. Monitor renal function and electrolytes, especially potassium, as ARB can cause hyperkalemia and HCTZ can cause hypokalemia. Avoid in pregnancy (Category D). Use with caution in renal artery stenosis. |
| Patient Advice | Take exactly as prescribed, usually once daily. · May cause dizziness; avoid driving until you know how you react. · Stay hydrated and avoid salt substitutes containing potassium. · Report symptoms of electrolyte imbalance: muscle cramps, weakness, irregular heartbeat. · Do not use if pregnant or planning pregnancy; use effective contraception. |