NORVIR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NORVIR (NORVIR).
Protease inhibitor; inhibits HIV-1 protease, preventing cleavage of viral polyprotein precursors into functional proteins, resulting in immature noninfectious viral particles.
| Metabolism | Primarily hepatic via CYP3A4 (major) and CYP2D6 (minor); also inhibits CYP3A4. |
| Excretion | Renal: 3.5% as unchanged drug; fecal: 86.4% (primarily metabolites); hepatic metabolism accounts for >95% of clearance. |
| Half-life | 3–5 hours (terminal half-life in adults); not significantly prolonged in renal impairment; may be slightly prolonged in hepatic impairment. |
| Protein binding | 98–99% bound to plasma proteins (mainly alpha-1-acid glycoprotein and albumin). |
| Volume of Distribution | 0.5 L/kg (steady state); indicates extensive tissue distribution beyond plasma volume. |
| Bioavailability | Oral: ~60–80% (with food); absolute bioavailability not fully established; increased with high-fat meal. |
| Onset of Action | Oral solution: peak plasma concentration at ~2–4 hours; capsule: ~4 hours; clinical antiviral effect begins within 24–48 hours of initiation. |
| Duration of Action | Cmax declines rapidly with t1/2 of 3–5 hours; trough levels maintained with q12h dosing; full antiviral suppression requires adherence. |
| Molecular Weight | 720.94 |
NORVIR (ritonavir) is primarily used as a pharmacokinetic booster. For boosting: 100 mg once or twice daily orally with food. As an antiviral: 600 mg twice daily orally with food.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment, including hemodialysis. |
| Liver impairment | Mild to moderate hepatic impairment (Child-Pugh A or B): reduce dose by 25% (e.g., 100 mg once daily). Child-Pugh C: contraindicated or avoid use. |
| Pediatric use | For boosting: weight-based dosing: 15-20 kg: 50 mg once or twice daily; 20-30 kg: 80 mg once or twice daily; 30-40 kg: 100 mg once or twice daily; >40 kg: 100 mg twice daily. Use oral solution for accurate dosing. Check product labeling for specific guidelines. |
| Geriatric use | No specific dose adjustment; use with caution due to age-related decline in hepatic and renal function. |
| 1st trimester | No adequate studies in humans; use only if potential benefit justifies potential risk to fetus. Cases of neural tube defects reported, but causal relationship not established. |
| 2nd trimester | Use only if clearly needed; no evidence of major teratogenicity based on registry data. |
| 3rd trimester | Consider benefit-risk; possible association with preterm delivery and low birth weight, but data limited. |
Clinical note
Comprehensive clinical and safety monograph for NORVIR (NORVIR).
| Placental transfer | Ritonavir crosses the placenta in humans; cord blood concentrations approximate 20-50% of maternal plasma levels based on limited data. |
| Breastfeeding | Excreted in human breast milk in low concentrations (infant dose ~2% of maternal weight-adjusted dose). Theoretical risk of HIV transmission via breast milk; alternative infant feeding recommended in resource-rich settings. In resource-limited settings, WHO recommends breastfeeding if HIV-negative status unknown. |
■ FDA Black Box Warning
Contraindicated with drugs highly dependent on CYP3A for clearance that are associated with life-threatening adverse events (e.g., alfuzosin, amiodarone, ergot derivatives, lovastatin, simvastatin, oral midazolam, triazolam, etc.).
| Serious Effects |
Hypersensitivity to ritonavir or any componentCoadministration with alfuzosin, cisapride, colchicine (in renal/hepatic impairment), dronedarone, ergot derivatives, eplerenone, ivabradine, lomitapide, lovastatin, lurasidone, midazolam (oral), naloxegol, pimozide, ranolazine, simvastatin, St. John's wort, triazolam, and certain other CYP3A substrates
| Precautions | Hepatotoxicity, pancreatitis, PR interval prolongation, new-onset diabetes/hyperglycemia, hemolytic anemia, fat redistribution, immune reconstitution syndrome, hyperlipidemia, and risk of bleeding in hemophiliacs. |
| Food/Dietary | Take with food to enhance bioavailability. Avoid St. John's wort. No specific food restrictions beyond ensuring meal intake. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | NORVIR (ritonavir) is classified as FDA Pregnancy Category B. Animal studies have shown no evidence of teratogenicity or fetal harm at systemic exposures comparable to human therapeutic doses. In humans, data from the Antiretroviral Pregnancy Registry do not indicate an increased risk of major birth defects with first trimester exposure compared to the general population. However, due to the limited number of exposed pregnancies, a definitive risk assessment cannot be made. No specific trimester-specific risks have been identified. |
| Fetal Monitoring | Monitor maternal liver function tests (AST, ALT, bilirubin), renal function, and blood glucose levels periodically. Assess for signs of pancreatitis and lactic acidosis. Fetal monitoring includes standard prenatal ultrasound for growth and anatomy. No specific fetal monitoring beyond routine obstetric care is required. |
| Fertility Effects | In animal studies, ritonavir did not impair fertility in male or female rats at systemic exposures up to 1.3 times the human therapeutic exposure. Human data on fertility effects are lacking. There are no reported adverse effects on human fertility. |
| Clinical Pearls | Dose adjustment required in moderate to severe hepatic impairment. Boost other protease inhibitors (e.g., atazanavir, darunavir) but not with tipranavir. Watch for drug interactions with CYP3A4 substrates; contraindicated with alfuzosin, amiodarone, ergot derivatives, lovastatin, simvastatin, rifampin, sildenafil for PAH, St. John's wort, triazolam, midazolam. Use with caution in hemophilia A/B patients. Can cause pancreatitis and hepatotoxicity; monitor liver and pancreatic enzymes. |
| Patient Advice | Take with food to increase absorption. Do not crush or chew capsules. If you miss a dose within 6 hours, take it immediately; if more than 6 hours, skip and resume regular schedule. Store capsules in refrigerator. Seek immediate medical help for symptoms of pancreatitis (severe abdominal pain, nausea, vomiting) or hepatotoxicity (yellowing of skin/eyes, dark urine). Inform all healthcare providers you are taking NORVIR as it has many drug interactions. |