ZELVYSIA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZELVYSIA (ZELVYSIA).
ZELVYSIA (molnupiravir) is a prodrug that is metabolized to the ribonucleoside analog NHC-triphosphate, which inhibits SARS-CoV-2 replication by inducing viral RNA mutagenesis via incorporation into viral RNA by the viral RNA-dependent RNA polymerase, leading to error catastrophe.
| Metabolism | Molnupiravir is metabolized to NHC by esterases in plasma and tissues. NHC is further phosphorylated intracellularly to NHC-triphosphate. NHC is metabolized primarily by uridine diphosphate glucuronosyltransferases (UGTs), with UGT1A9 as the major enzyme involved. |
| Excretion | Primarily renal excretion (70% as unchanged drug); additional 20% fecal/biliary; 10% metabolized. |
| Half-life | Terminal elimination half-life is 3.5 hours (range 2.5–5 hours); clinically relevant for dosing interval adjustments in renal impairment. |
| Protein binding | 80% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 1.2 L/kg (indicating extensive extravascular distribution; penetrates tissues including CNS). |
| Bioavailability | Oral: 65% (first-pass metabolism reduces absorption; food decreases bioavailability by 20%). |
| Onset of Action | Oral: 1–2 hours; Intravenous: 15–30 minutes. |
| Duration of Action | 8–12 hours (clinical effect correlates with plasma levels >0.5 µg/mL); extended in hepatic impairment. |
For uncomplicated Gram-negative infection: 30 mg/kg intravenous loading dose over 1 hour, followed by 10 mg/kg intravenous maintenance dose over 1 hour every 24 hours. For complicated infections: 30 mg/kg loading, then 20 mg/kg every 24 hours. Infuse over 2 hours for maintenance doses.
| Dosage form | POWDER |
| Renal impairment | For CrCl 30-59 mL/min: 20 mg/kg loading, then 10 mg/kg every 24 hours. For CrCl 15-29 mL/min: 20 mg/kg loading, then 10 mg/kg every 48 hours. For CrCl <15 mL/min or hemodialysis: 10 mg/kg loading, then 4 mg/kg every 48 hours. Administer after dialysis on dialysis days. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use with caution. |
| Pediatric use | Dosing not established for patients <18 years. Safety and efficacy in pediatric patients have not been studied. |
| Geriatric use | No specific dose adjustment based on age alone. Adjust dose based on renal function as CrCl declines with age. Monitor renal function closely and follow renal adjustment guidelines. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZELVYSIA (ZELVYSIA).
| Breastfeeding | Lapatinib is excreted into human milk. A study in lactating women reported a milk-to-plasma (M/P) ratio of approximately 0.2. However, the amount ingested by a nursing infant is estimated to be subtherapeutic. Due to the potential for serious adverse reactions in the breastfed infant from lapatinib exposure, advise lactating women not to breastfeed during therapy and for at least 1 week after the last dose. |
| Teratogenic Risk | ZELVYSIA (lapatinib) is categorized as Pregnancy Category D. There is evidence of fetal risk based on human data. In animal studies, lapatinib caused fetal toxicity and teratogenic effects at maternal doses lower than the recommended human dose. First trimester exposure carries a risk of major congenital malformations including cardiovascular and skeletal defects. Second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and potential placental dysfunction. Use is contraindicated in pregnant women unless no alternative therapy exists. |
■ FDA Black Box Warning
No boxed warning exists for ZELVYSIA.
| Serious Effects |
["ZELVYSIA is contraindicated in patients with known hypersensitivity to molnupiravir or any of its components."]
| Precautions | ["ZELVYSIA is not authorized for use in patients less than 18 years of age.","ZELVYSIA is not recommended for use during pregnancy. Women of childbearing potential should use effective contraception during treatment and for 4 days after the final dose.","ZELVYSIA may cause fetal harm. Embryo-fetal toxicity has been observed in animal reproduction studies.","No clinically significant drug-drug interactions have been identified.","ZELVYSIA should not be used for longer than 5 days."] |
Loading safety data…
| Fetal Monitoring | Monitor maternal liver function tests (ALT, AST, bilirubin) monthly due to hepatotoxicity. Assess left ventricular ejection fraction (LVEF) by echocardiogram or MUGA scan baseline and every 3 months during therapy due to cardiotoxicity. Perform ultrasound fetal growth assessment every 4-6 weeks to detect intrauterine growth restriction or oligohydramnios. Monitor for signs of maternal hypertension and proteinuria. Evaluate for fetal cardiac anomalies via fetal echocardiogram if exposed during first trimester. |
| Fertility Effects | Lapatinib may impair fertility in females based on animal studies showing prolonged estrus cycles and reduced fertility indices. In male rats, testicular degeneration and decreased sperm motility were observed. Human data are limited; however, reversible menstrual irregularities have been reported. Advise patients of potential impact on fertility and discuss fertility preservation options prior to treatment. |