Indinavir

Indinavir Overview

Indinavir (chemical formula C36H47N5O4) is a potent, synthetic peptidomimetic HIV-1 protease inhibitor. Chemically, it belongs to the class of organic compounds known as alpha amino acid amides within the organic acids superclass. Structurally, it features a hydroxyethylene core transition-state isostere incorporating an indane group, a tert-butylamide group, a piperazine ring, and a pyridinylmethyl side chain.

What Is Indinavir and How Does It Work?

Indinavir acts primarily through competitive active-site inhibition of the HIV-1 aspartyl protease enzyme.

Its primary chemical, physiological, and viral mechanisms include:

• Targeting the HIV-1 Protease Active Site: Late in the HIV replication cycle, the virus buds from the host cell membrane as an immature, non-infectious virion containing intact viral Gag and Gag-Pol polyproteins. HIV-1 protease, a homodimeric aspartyl protease is responsible for cleaving these precursor polyproteins into functional structural proteins (p17, p24, p7) and essential enzymes (reverse transcriptase, integrase, protease).
• Peptidomimetic Transition-State Mimicry: Indinavir mimics the transition state of the natural polyprotein cleavage site. It fits tightly into the substrate-binding pocket of the HIV-1 protease homodimer, forming hydrogen bonds with catalytic aspartic acid residues (Asp25 and Asp25′).
• Prevention of Polyprotein Cleavage: Occupying the active site prevents the catalytic cleavage of viral Gag and Gag-Pol polyproteins.

Is Indinavir FDA Approved?

Yes, Indinavir sulfate (Crixivan) was approved by the US FDA in March 1996 as a prescription antiretroviral for the treatment of HIV-1 infection in combination with other antiretroviral medications.

What Is Indinavir Used For?

• Treatment of HIV-1 infection in combination with other antiretroviral agents (e.g., nucleoside reverse transcriptase inhibitors / NRTIs) in adults and pediatric patients.

Before Taking Indinavir: Warnings & Precautions

Screen for severe hypersensitivity to indinavir or capsule excipients. Indinavir is poorly soluble in neutral urine and crystallizes in the renal system, causing nephrolithiasis, renal colic, and acute renal failure in 10% to 20% of patients; maintaining a daily fluid intake of at least 1.5 to 2 liters is mandatory. Strictly contraindicated with potent CYP3A4 inducers (rifampin, St. John’s wort) or sensitive CYP3A4 substrates associated with severe toxicity (simvastatin, lovastatin, amiodarone, triazolam). Use during pregnancy is generally avoided due to low third-trimester drug exposure, and mothers with HIV-1 should refrain from breastfeeding to prevent viral transmission.

Clinical Safety Warnings

Indinavir carries critical clinical safety warnings regarding Nephrolithiasis & Renal Insufficiency, Hyperbilirubinemia, Metabolic Derangements, and Severe Drug Interactions:

• Nephrolithiasis & Urolithiasis: Indinavir is poorly soluble at neutral urinary pH. It crystallizes in the renal collecting system, causing nephrolithiasis (kidney stones), flank pain, hematuria, renal colic, and acute renal failure in 10% to 20% of patients. High daily fluid intake is mandatory.
• Indirect Hyperbilirubinemia: Indinavir inhibits human UDP-glucuronosyltransferase 1A1 (UGT1A1), preventing bilirubin conjugation and producing asymptomatic indirect (unconjugated) hyperbilirubinemia and jaundice in up to 10% to 15% of patients.
• Lipodystrophy & Metabolic Derangements: Long-term therapy causes metabolic syndrome, including central obesity (“crix belly”), buffalo hump, peripheral fat wasting, hypertriglyceridemia, insulin resistance, and new-onset diabetes mellitus.
• Hemophilia Bleeding: Spontaneous bleeding episodes (hemarthroses and soft tissue hematomas) can occur in patients with hemophilia Type A or B.

Who Should Not Take Indinavir?

• Individuals with a documented severe hypersensitivity to Indinavir or capsule formulation excipients.
• Co-administration with drugs that depend heavily on CYP3A4 for clearance and for which elevated plasma concentrations cause life-threatening toxicity (e.g., alfuzosin, amiodarone, pimozide, triazolam, midazolam, ergot alkaloids, lovastatin, simvastatin).
• Co-administration with potent CYP3A4 inducers that markedly lower Indinavir blood levels (e.g., rifampin, St. John’s wort).

Indinavir, Pregnancy & Lactation

Indinavir crosses the placental barrier, but fetal drug exposure is significantly lower than maternal plasma levels due to active placental P-glycoprotein efflux pumps. Because unboosted Indinavir pharmacokinetic levels drop significantly during the third trimester, it is not recommended as a preferred protease inhibitor in pregnant women. Mothers with HIV-1 infection should avoid breastfeeding to prevent vertical transmission of HIV-1 to the infant.

Tell Your Doctor Before Taking Indinavir

Inform your infectious disease specialist or physician if you have a history of kidney stones, liver disease, hepatitis B or C, diabetes, hemophilia, high cholesterol, or severe drug allergies.

Indinavir Dosage & Administration

Standard unboosted adult dosing is 800 mg (two 400-mg capsules) taken orally every 8 hours around the clock. Standard ritonavir-boosted adult dosing is 800 mg taken orally twice daily alongside low-dose ritonavir (100 mg twice daily). Pediatric dosing is 500 mg/m2 body surface area orally every 8 hours (maximum 800 mg per dose). Reduce dose to 600 mg every 8 hours in patients with mild-to-moderate hepatic cirrhosis.

Standard Dosing Guidelines

• Adult Dosing (Unboosted Regimen): Standard dosage is 800 mg (two 400-mg capsules) taken orally every 8 hours (three times daily) around the clock.
• Adult Dosing (Ritonavir-Boosted Regimen): 800 mg taken orally twice daily combined with low-dose ritonavir (100 mg orally twice daily) as a pharmacokinetic booster.
• Pediatric Dosing: 500 mg/m2 of body surface area taken orally every 8 hours (maximum 800 mg every 8 hours).
• Hepatic Impairment Dosing: In patients with mild-to-moderate hepatic insufficiency secondary to cirrhosis, reduce dosage to 600 mg taken orally every 8 hours.

How Indinavir Is Administered

• Strict Hydration Rule: Patients MUST drink at least 1.5 to 2 liters (approx. 48 to 64 fluid ounces) of water daily to ensure adequate urine output and prevent drug crystallization in the kidneys.
• Unboosted Administration: Take unboosted Indinavir on an empty stomach with water 1 hour before or 2 hours after meals, OR take with a light, non-fat meal (e.g., dry toast with jelly, skim milk, or juice). High-fat, high-protein, or high-calorie meals reduce drug absorption by over 70%.
• Ritonavir-Boosted Administration: When taken with low-dose ritonavir, Indinavir may be taken without regard to food timing or fat content.

Indinavir Clinical Efficacy & Research

Pivotal Phase 3 clinical trials in the mid-1990s established that adding Indinavir to zidovudine and lamivudine (triple-drug HAART) produced profound, unprecedented reductions in HIV-1 RNA viral load to undetectable levels (< 50 copies/mL) and substantial CD4 T-cell count increases (> 100 to 150 cells/mm3). This triple-combination regimen yielded dramatic reductions in AIDS-defining opportunistic infections and mortality.

Indinavir Side Effects & Safety Profile

Competitively inhibits the active site of HIV-1 aspartyl protease, preventing the cleavage of viral Gag and Gag-Pol polyproteins and generating immature, non-infectious virions. Common side effects include nephrolithiasis, dysuria, nausea, metallic taste, dry skin, paronychia, and indirect hyperbilirubinemia from UGT1A1 enzyme inhibition. Serious risks include acute tubulointerstitial nephritis, severe lipodystrophy (“crix belly”), new-onset diabetes, hemolytic anemia, and spontaneous bleeding in hemophiliacs.

Common Side Effects

• Renal / Genitourinary: Nephrolithiasis, flank pain, dysuria, hematuria, and crystalluria.
• Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, regurgitation, and metallic taste.
• Dermatological: Dry skin, pruritus, paronychia (painful nail bed inflammation), alopecia, and ingrown toenails.
• Hepatic / Metabolic: Indirect hyperbilirubinemia, asymptomatic transaminase elevations, and fatigue.

Serious Adverse Events

• Nephrolithiasis & Tubulointerstitial Nephritis: Renal colic, ureteral obstruction, and acute or chronic interstitial nephritis leading to renal failure.
• Severe Metabolic Derangements: New-onset diabetes mellitus, diabetic ketoacidosis, severe hypertriglyceridemia, and accelerated cardiovascular disease.
• Hemolytic Anemia: Acute hemolytic anemia associated with severe hyperbilirubinemia.
• Severe SCARs & Hypersensitivity: Rare Stevens-Johnson syndrome (SJS) and erythema multiforme.

Managing Side Effects

If renal colic or flank pain occurs, withhold Indinavir temporarily, administer aggressive IV or oral hydration, manage pain, and resume once stones pass. If unconjugated hyperbilirubinemia occurs without transaminase elevation, it is benign and does not require treatment cessation unless severe jaundice causes cosmetic distress.

Indinavir Drug Interactions & What to Avoid

Indinavir is both a substrate and a potent competitive inhibitor of CYP3A4, P-glycoprotein, and UGT1A1. Co-administration with simvastatin or lovastatin is strictly contraindicated due to severe rhabdomyolysis risks. Potent CYP3A4 inducers significantly lower indinavir concentrations and cause viral treatment failure, while PDE-5 inhibitors (sildenafil) require reduced initial doses to prevent severe hypotension. Avoid alcohol, which worsens dehydration, gastrointestinal irritation, and hepatic strain.

Drug-Drug Interactions

Indinavir is both a substrate and a potent competitive inhibitor of Cytochrome P450 CYP3A4, as well as a substrate and inhibitor of P-glycoprotein (P-gp) and UGT1A1:

• Contraindicated CYP3A4 Substrates (Severe Toxicity): Alfuzosin, amiodarone, pimozide, ergotamine, triazolam, oral midazolam, lovastatin, and simvastatin (causes severe rhabdomyolysis and myopathy).
• Potent CYP3A4 Inducers (Decreased Indinavir Efficacy): Rifampin, St. John’s wort, carbamazepine, and phenobarbital markedly lower Indinavir blood concentrations, leading to treatment failure and viral resistance.

Food & Alcohol

High-fat, high-calorie meals reduce unboosted Indinavir absorption. Always take unboosted doses on an empty stomach or with a light non-fat snack. Avoid alcohol, which worsens gastrointestinal irritation, dehydration, and liver strain.

Indinavir Overdose, Emergency & Clearance

Absorbed rapidly under fasting conditions with peak levels achieved in 0.8 to 1 hour and an elimination half-life of 1.8 to 2 hours, undergoing extensive hepatic CYP3A4 metabolism with primary fecal excretion. Overdose causes severe flank pain, gross hematuria, acute renal failure, and severe vomiting. Treatment is supportive, relying on aggressive IV hydration to force urinary output and prevent massive intra-renal crystallization; hemodialysis is ineffective.

Elimination Kinetics & Overdose

Following oral administration, Indinavir is rapidly absorbed under fasting conditions, reaching peak plasma concentrations (Cmax) within 0.8 to 1 hour. It is bound moderately to human plasma proteins (approx. 60%). It undergoes extensive hepatic metabolism via Cytochrome P450 CYP3A4 into seven minor oxidative metabolites. It is excreted primarily in feces (approx. 83%, containing unchanged drug and metabolites) and renally (approx. 19% recovered in urine, with 11% as unchanged parent drug).

Storage & Handling

Store capsules in their original glass container at controlled room temperature between 15°C and 30°C (59°F to 86°F). Indinavir capsules are extremely sensitive to moisture; keep the original desiccant pouch inside the bottle at all times and keep the container tightly closed. Do not store in humid bathroom cabinets. Keep strictly out of reach of children.

Indinavir Patient Management & Safety Protocols

Enforce a daily intake of at least 1.5 to 2 liters of water to prevent crystalluria and kidney stone formation. Monitor plasma HIV-1 RNA viral load, CD4 T-cell counts, liver function panels, fasting lipids, and blood glucose every 3 to 4 months. Perform baseline and periodic urinalysis and renal function tests (serum creatinine, BUN) to detect early nephrotoxicity.

Clinical Monitoring Checklist

• Enforce daily fluid intake of at least 1.5 to 2 liters of water daily.
• Monitor plasma HIV-1 RNA viral load and CD4 T-cell counts every 3 to 4 months.
• Perform baseline and periodic urinalysis (check for crystals, red blood cells), serum creatinine, and BUN.
• Monitor baseline and periodic liver function tests (total/direct bilirubin, ALT, AST) and fasting lipid panel/glucose.
• Screen all concurrent medications for CYP3A4 interactions before starting therapy.

Key Do’s and Don’ts

• Do drink at least 1.5 to 2 liters (48 to 64 oz) of water every day.
• Do take unboosted doses on an empty stomach or with a light non-fat meal.
• Do keep capsules in their original bottle with the desiccant packet tightly closed.
• Do report flank pain, blood in urine, or yellowing of eyes/skin immediately.
• Do not take with high-fat or high-calorie meals.
• Do not take statins like lovastatin or simvastatin while on Indinavir.
• Do not miss or delay doses, as strict 8-hour timing prevents viral drug resistance.

Frequently Asked Questions

References

• DrugBank Database – Indinavir Profile (DB00224)
• Official FDA Prescribing Information – Crixivan (Indinavir Sulfate Capsules)

Legal Disclaimer

The detailed medical and chemical information provided on this specific web page is intended strictly for educational and informational purposes regarding complex pharmacological mechanisms. It absolutely does not constitute professional medical advice, medical diagnosis, or specific treatment recommendations. Always consult a licensed healthcare provider before making any personal decisions regarding complex medical conditions, medication adjustments, or dietary changes.