TOLVAPTAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TOLVAPTAN (TOLVAPTAN).
Selective vasopressin V2 receptor antagonist; inhibits arginine vasopressin (AVP) binding at V2 receptors of the renal collecting duct, increasing water excretion without affecting sodium or potassium excretion.
| Metabolism | Primarily hepatic via CYP3A4; minor contribution from CYP3A5 and CYP2C19; drug is a substrate of P-glycoprotein. |
| Excretion | Primarily hepatic metabolism (<1% excreted unchanged in urine); fecal excretion accounts for ~40% of the dose, with renal excretion of metabolites ~55%. |
| Half-life | Terminal half-life ~12 hours (range 8–16 hours) in healthy subjects; prolonged in hepatic impairment (Child-Pugh B/C) and in elderly (up to 20 hours). |
| Protein binding | ~99% bound to albumin (primarily), with minor binding to α1-acid glycoprotein. |
| Volume of Distribution | Vd ~2–3 L/kg (200–300 L for a 70-kg adult), indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability ~40–60% (absolute) in fasting state; food may reduce rate but not extent of absorption. |
| Onset of Action | Oral: 2–4 hours for aquaresis (urine output increase); maximal effect within 4–8 hours. |
| Duration of Action | Aquarctic effect persists 12–24 hours after a single oral dose; chronic dosing maintains effect, but tolerance may develop with prolonged use. |
15 mg orally once daily, titrated to 30 mg once daily after 24 hours, then to 60 mg once daily as tolerated. Maximum dose 60 mg daily.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR ≥10 mL/min. Contraindicated if GFR <10 mL/min or anuric patients. |
| Liver impairment | Contraindicated in Child-Pugh class B and C. No dose adjustment for Child-Pugh class A. |
| Pediatric use | Not FDA-approved for pediatric patients; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment; initiate at 15 mg once daily with caution due to age-related decreased renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TOLVAPTAN (TOLVAPTAN).
| Breastfeeding | It is unknown if tolvaptan is excreted in human breast milk. Due to the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. No M/P ratio is available. |
| Teratogenic Risk | Tolvaptan is pregnancy category C. There are no adequate and well-controlled studies in pregnant women. In animal studies, tolvaptan caused cleft palate, brachymelia, and microphthalmia in rats and rabbits at doses 1-4 times the human exposure. Given the potential for teratogenicity, tolvaptan should be avoided during the first trimester and used during pregnancy only if the potential benefit justifies the potential risk to the fetus. |
■ FDA Black Box Warning
WARNING: (A) INITIATE AND RE-INITIATE IN A HOSPITAL SETTING, TOO RAPID CORRECTION OF HYPONATREMIA CAN CAUSE OSMOTIC DEMYELINATION SYNDROME. (B) NOT FOR USE IN PATIENTS WITH AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD) OUTSIDE OF FDA-APPROVED INDICATIONS
| Serious Effects |
Hypovolemic hyponatremia; anuria; inability to sense or respond to thirst; hypernatremia; concomitant use of strong CYP3A4 inhibitors; ADPKD (outside approved indication); urgent need to raise serum sodium (e.g., seizures); uncorrected adrenal insufficiency; known hypersensitivity
| Precautions | Too rapid correction of hyponatremia (risk of osmotic demyelination); hepatic injury (elevated transaminases and potential liver failure); volume depletion; hyperkalemia; hypovolemia; acute renal failure; need to restrict fluid intake during therapy; contraindicated in patients with anuria, hypovolemia, or hypernatremia. |
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| Fetal Monitoring | Monitor serum sodium levels closely to avoid overly rapid correction of hyponatremia, which can cause osmotic demyelination syndrome. Regular monitoring of liver function tests due to risk of hepatotoxicity. In pregnancy, monitor fetal growth and amniotic fluid volume via ultrasound, as tolvaptan may cause dehydration and affect fetal fluid balance. |
| Fertility Effects | In animal studies, tolvaptan did not impair fertility in male or female rats at exposures up to 16 times human exposure. No human data available. |