Indinavir: Potent Protease Inhibition for HIV Management
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Synonyms | |||
Indinavir is an antiretroviral medication classified as a protease inhibitor, specifically developed for the treatment of Human Immunodeficiency Virus (HIV) infection. It functions by selectively inhibiting the HIV-1 protease enzyme, a critical component in the viral replication process. This inhibition prevents the cleavage of viral polyprotein precursors into functional proteins, resulting in the production of immature, non-infectious viral particles. As a cornerstone of Highly Active Antiretroviral Therapy (HAART), indinavir is used in combination with other antiretroviral agents to suppress viral load, increase CD4 cell counts, and slow disease progression. Its role is particularly significant in treatment-naïve patients and as part of salvage regimens, contributing to improved long-term clinical outcomes.
Features
- Active pharmaceutical ingredient: Indinavir sulfate
- Standard formulation: 200 mg, 400 mg capsules
- Mechanism: Selective inhibition of HIV-1 protease
- Bioavailability: Approximately 65% under fasting conditions
- Plasma protein binding: Approximately 60%
- Metabolism: Hepatic, primarily via CYP3A4 isoenzyme
- Elimination half-life: 1.5–2 hours
- Excretion: Primarily fecal (<20% renal)
Benefits
- Significantly reduces HIV viral load in plasma
- Increases CD4+ T-cell counts, improving immune function
- Delays progression to AIDS-defining illnesses
- Enhances overall survival rates in HIV-positive individuals
- Can be used as part of combination therapy to prevent resistance
- Contributes to long-term virological suppression when adherence is maintained
Common use
Indinavir is indicated for the treatment of HIV-1 infection in adults and pediatric patients older than 4 years, in combination with other antiretroviral agents. It is typically prescribed as part of a triple-drug regimen, most commonly with two nucleoside reverse transcriptase inhibitors (NRTIs). Its use is guided by genotypic or phenotypic resistance testing when available, particularly in treatment-experienced patients. The medication is also employed in post-exposure prophylaxis (PEP) regimens following occupational or non-occupational exposure to HIV, though this is off-label use requiring careful risk-benefit assessment.
Dosage and direction
The recommended adult dosage is 800 mg (two 400 mg capsules) orally every 8 hours. Administration must occur on an empty stomach, either 1 hour before or 2 hours after a meal, or with a light, low-fat snack to optimize absorption. Pediatric dosing is based on body surface area: 500 mg/m² every 8 hours. Dosage adjustment is required in patients with hepatic impairment: moderate impairment (Child-Pugh score 5–6) requires reduction to 600 mg every 8 hours. Adequate hydration (at least 1.5 liters daily) is essential to reduce risk of nephrolithiasis. The medication should be taken at consistent intervals to maintain therapeutic plasma concentrations.
Precautions
Hydration status must be carefully monitored, as indinavir is associated with nephrolithiasis in approximately 10% of patients. Liver function tests should be performed at baseline and periodically during treatment due to potential hepatotoxicity. Patients with hemophilia may experience increased bleeding frequency. Hyperglycemia and new-onset diabetes mellitus have been reported; glucose monitoring is advised. Fat redistribution (lipodystrophy) and lipid abnormalities (hypertriglyceridemia, hypercholesterolemia) may occur. Concomitant use with medications that affect CYP3A4 requires careful management. Pregnancy category C: use only if potential benefit justifies potential risk to fetus.
Contraindications
Hypersensitivity to indinavir or any component of the formulation. Coadministration with drugs highly dependent on CYP3A4 for clearance and with narrow therapeutic indices (e.g., alfuzosin, amiodarone, ergot derivatives, cisapride, pimozide, quinidine, triazolam). Concurrent use with strong CYP3A4 inducers such as rifampin, St. John’s wort, or lovastatin/simvastatin. Severe hepatic impairment. History of nephrolithiasis during previous indinavir therapy unless benefits outweigh risks and adequate hydration can be maintained.
Possible side effect
- Nephrolithiasis (9–12% of patients)
- Asymptomatic hyperbilirubinemia (10–15%)
- Nausea (12%), abdominal pain (9%), diarrhea (5%)
- Headache (5–9%), dizziness (6%)
- Rash (3–5%), dry skin, pruritus
- Asthenia (5–7%)
- Elevated liver transaminases (2–4%)
- Hyperglycemia (3–5%)
- Lipodystrophy (2–4%)
- Hemolytic anemia (<1%)
- Thrombocytopenia (<1%)
Drug interaction
Strong CYP3A4 inhibitors (ketoconazole, itraconazole): increase indinavir AUC by 60–70%; reduce indinavir dose to 600 mg every 8 hours. CYP3A4 inducers (rifampin, carbamazepine): decrease indinavir AUC by 80–90%; contraindicated. Didanosine: administer at least 1 hour apart due to formulation interactions. Atorvastatin: possible increased statin levels; use lowest possible dose. Sildenafil: AUC increased 3–4 fold; maximum sildenafil dose 25 mg in 48 hours. Midazolam, triazolam: contraindicated due to prolonged sedation risk. Ethinyl estradiol: AUC decreased by 40%; alternative contraception recommended.
Missed dose
If a dose is missed by less than 2 hours, take it immediately. If more than 2 hours have passed, skip the missed dose and resume the regular dosing schedule. Do not double the next dose to make up for the missed one. Maintaining consistent 8-hour intervals is critical for virological suppression and resistance prevention. Patients should be counseled on the importance of adherence and provided with strategies (e.g., pill organizers, alarms) to minimize missed doses.
Overdose
Limited experience with overdose. Single doses up to 2.4 g have been administered without severe effects. Potential manifestations may include nephrolithiasis, nausea, vomiting, diarrhea, and abdominal pain. Management is supportive: gastric lavage if presented early, activated charcoal, and adequate hydration to promote renal excretion. Hemodialysis is unlikely to be effective due to high protein binding. Monitor renal function, electrolyte balance, and hepatic parameters. Contact poison control center for specific management guidance.
Storage
Store at controlled room temperature (20–25°C or 68–77°F). Excursions permitted between 15–30°C (59–86°F). Keep container tightly closed and protect from moisture. Dispense in original container with desiccant. Do not remove desiccant from bottle. Keep out of reach of children and pets. Do not use after expiration date printed on packaging. Do not transfer capsules to other containers as stability may be compromised.
Disclaimer
This information is for educational purposes only and does not constitute medical advice. Treatment decisions must be made by qualified healthcare professionals based on individual patient characteristics. The prescribing physician should be consulted for specific dosage recommendations and management of adverse effects. This monograph does not cover all possible uses, directions, precautions, or interactions. Healthcare providers should reference complete prescribing information and current treatment guidelines before initiating therapy.
Reviews
Clinical trials demonstrate indinavir’s efficacy in combination therapy, with 70–80% of treatment-naïve patients achieving viral loads <500 copies/mL at 24 weeks. Long-term studies show durable suppression in adherent patients. Real-world evidence confirms effectiveness but notes higher discontinuation rates due to side effects compared to newer protease inhibitors. Specialist consensus recognizes its historical importance while noting modern regimens often prefer better-tolerated alternatives. Patient-reported outcomes indicate satisfaction with virological control but frequent concerns about dosing frequency and nephrolithiasis risk.