indication

Indinavir is an antiretroviral drug for the treatment of HIV infection.

pharmacology

Indinavir is a protease inhibitor with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Protease inhibitors block the part of HIV called protease. HIV-1 protease is an enzyme required for the proteolytic cleavage of the viral polyprotein precursors into the individual functional proteins found in infectious HIV-1. Indinavir binds to the protease active site and inhibits the activity of the enzyme. This inhibition prevents cleavage of the viral polyproteins resulting in the formation of immature non-infectious viral particles. Protease inhibitors are almost always used in combination with at least two other anti-HIV drugs.

mechanism of action

Indinavir inhibits the HIV viral protease enzyme which prevents cleavage of the gag-pol polyprotein, resulting in noninfectious, immature viral particles.

toxicity

Symptoms of overdose include myocardial infarction and angina pectoris.

biotransformation

Hepatic. Seven metabolites have been identified, one glucuronide conjugate and six oxidative metabolites. In vitro studies indicate that cytochrome P-450 3A4 (CYP3A4) is the major enzyme responsible for formation of the oxidative metabolites.

absorption

Rapidly absorbed

half life

1.8 (± 0.4) hours

route of elimination

Less than 20% of indinavir is excreted unchanged in the urine.

drug interactions

Abacavir: The serum concentration of Abacavir may be decreased by protease inhibitors such as Indinavir. The antiviral response should be closely monitored.

Acenocoumarol: The protease inhibitor, indinavir, may increase the anticoagulant effect of acenocoumarol.

Alprazolam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, alprazolam.

Aluminium: The antacid decreases the absorption of indinavir

Amiodarone: Indinavir increases the effect and toxicity of amiodarone

Anisindione: The protease inhibitor, indinavir, may increase the anticoagulant effect of anisindione.

Astemizole: Increased risk of cardiotoxicity and arrhythmias

Atazanavir: Increased risk of hyperbilirubinemia with this association

Atorvastatin: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of atorvastatin by decreasing its metabolism. Concomitant therapy is contraindicated.

Bromazepam: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of bromazepam by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of bromazepam if indinavir is initiated, discontinued or dose changed. Dosage adjustments may be required.

Calcium: Calcium may decrease the absorption of indinavir.

Carbamazepine: Indinavir increases the effect and toxicity of carbamazepine

Chlordiazepoxide: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, chlordiazepoxide.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Clarithromycin: Indinavir may decrease the effectiveness of clarithromycin by decreasing the formatin of the active metabolite, 14-hydroxy-clarithromycin. Clarithromycin may increase the serum concentration of indinavir. Indinavir may increase the serum concentration of clarithromycin. Consider alternate therapy or monitor the efficacy and adverse effects of both agents more closely during concomitant therapy.

Clonazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, clonazepam.

Clorazepate: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, clorazepate.

Cyclosporine: The protease inhibitor, indinavir, may increase the effect of cyclosporine.

Dantrolene: Indinavir may increase the serum concentration of dantrolene by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of dantrolene if indinavir is initiated, discontinued or dose changed.

Delavirdine: Delavirdine may increase the effect of indinavir.

Diazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, diazepam.

Dicumarol: The protease inhibitor, indinavir, may increase the anticoagulant effect of dicumarol.

Dihydroergotamine: Indinavir may increase the serum concentration of dihydroergotamine. Concomitant therapy is contraindicated.

Efavirenz: Efavirenz decreases the effect of indinavir

Ergotamine: Indinavir may increase the serum concentration of ergotamine. Concomitant therapy is contraindicated.

Erlotinib: This CYP3A4 inhibitor increases levels/toxicity of erlotinib

Esomeprazole: Omeprazole decreases the absorption of indinavir

Estazolam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, estazolam.

Fentanyl: The protease inhibitor, indinavir, may increase the effect and toxicity of fentanyl.

Flurazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, flurazepam.

Fusidic Acid: Indinavir may increase the effect and toxicity of fusidic acid.

Halazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, halazepam.

Ketoconazole: Indinavir may increase the serum concentration of ketoconazole. Ketoconazole may increase the serum concentration of indinavir. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of both agents if either agent is initiated, discontinued or dose changed.

Lansoprazole: Omeprazole decreases the absorption of indinavir

Lovastatin: Indinavir may increase the effect and toxicity of lovastatin. Concomitant therapy is contraindicated.

Magnesium: Magnesium may decrease the absorption of indinavir.

Magnesium oxide: The antacid decreases the absorption of indinavir

Midazolam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, midazolam.

Omeprazole: Omeprazole decreases the absorption of indinavir

Pantoprazole: Omeprazole decreases the absorption of indinavir

Pimozide: The protease inhibitor, indinavir, may increase the effect and toxicity of pimozide.

Prazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, prazepam.

Quazepam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, quazepam.

Quinupristin: This combination presents an increased risk of toxicity

Rabeprazole: Omeprazole decreases the absorption of indinavir

Ranolazine: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of ranolazine by decreasing its metabolism. Concomitant therapy is contraindicated.

Rifabutin: Rifabutin decreases the effect of indinavir

Rifampin: Rifampin decreases the effect of indinavir

Risperidone: Increased risk of extrapyramidal symptoms

Saquinavir: Possible antagonism of action

Sildenafil: The protease inhibitor, indinavir, may increase the effect and toxicity of sildenafil.

St. John's Wort: St. John's Wort decreases the effect of indinavir

Sunitinib: Possible increase in sunitinib levels

Tacrolimus: The protease inhibitor, Indinavir, may increase the blood concentration of Tacrolimus. Monitor for changes in the therapeutic/toxic effects of Tacrolimus if Indinavir therapy is initiated, discontinued or altered.

Tadalafil: Indinavir may reduce the metabolism of Tadalafil. Concomitant therapy should be avoided if possible due to high risk of Tadalafil toxicity.

Tamoxifen: Indinavir may increase the serum concentration of Tamoxifen by decreasing its metabolism. Monitor for increased adverse/toxic effects of Tamoxifen.

Tamsulosin: Indinavir, a CYP3A4 inhibitor, may decrease the metabolism and clearance of Tamsulosin, a CYP3A4 substrate. Monitor for changes in therapeutic/adverse effects of Tamsulosin if Indinavir is initiated, discontinued, or dose changed.

Telithromycin: Indinavir may increase the plasma concentration of Telithromycin. Consider alternate therapy or monitor therapeutic/adverse effects.

Temsirolimus: Indinavir may inhibit the metabolism and clearance of Temsirolimus. Concomitant therapy should be avoided.

Teniposide: The strong CYP3A4 inhibitor, Indinavir, may decrease the metabolism and clearance of Teniposide, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Teniposide if Indinavir is initiated, discontinued or dose changed.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Tiagabine: The strong CYP3A4 inhibitor, Indinavir, may decrease the metabolism and clearance of Tiagabine, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Tiagabine if Indinavir is initiated, discontinued or dose changed.

Tolterodine: Indinavir may decrease the metabolism and clearance of Tolterodine. Adjust Tolterodine dose and monitor for efficacy and toxicity.

Tramadol: Indinavir may increase Tramadol toxicity by decreasing Tramadol metabolism and clearance.

Trazodone: The protease inhibitor, Indinavir, may increase the efficacy/toxicity of Trazodone by inhibiting Trazodone metabolism via CYP3A4. Monitor for changes in Trazodone efficacy/toxicity if Indinavir is initiated, discontinued or dose changed.

Triazolam: The protease inhibitor, indinavir, may increase the effect of the benzodiazepine, triazolam.

Trimipramine: The strong CYP3A4 inhibitor, Indinavir, may decrease the metabolism and clearance of Trimipramine, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in therapeutic and adverse effects of Trimipramine if Indinavir is initiated, discontinued or dose changed.

Vardenafil: Indinavir, a potent CYP3A4 inhibitor, may decrease the metabolism and clearance of Vardenafil. Concomitant therapy is contraindicated.

Venlafaxine: Indinavir, a CYP3A4 inhibitor, may decrease the metabolism and clearance of Venlafaxine, a CYP3A4 substrate. Monitor for changes in therapeutic/adverse effects of Venlafaxine if Indinavir is initiated, discontinued, or dose changed.

Verapamil: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of Veramapil, a CYP3A4 substrate, by decreasing its metabolism and clearance. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Verapamil if Indinavir is initiated, discontinued or dose changed.

Vinblastine: Indinavir, a strong CYP3A4 inhibitor, may decrease the metabolism of Vinblastine. Consider alternate therapy to avoid Vinblastine toxicity. Monitor for changes in the therapeutic/adverse effects of Vinblastine if Indinavir is initiated, discontinued or dose changed.

Vincristine: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of Vincristine by decreasing its metabolism. Consider alternate therapy to avoid Vincristine toxicity. Monitor for changes in the therapeutic and adverse effects of Vincristine if Indinavir is initiated, discontinued or dose changed.

Vinorelbine: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of Vinorelbine by decreasing its metabolism. Consider alternate therapy to avoid Vinorelbine toxicity. Monitor for changes in the therapeutic and adverse effects of Vinorelbine if Indinavir is initiated, discontinued or dose changed.

Vitamin C: Vitamin C decreases indinavir levels

Voriconazole: Voriconazole may increase the serum concentration of indinavir by decreasing its metabolism. Indinavir may increase the serum concentration of voriconazole. Monitor for changes in the therapeutic and adverse effects of both agents if concomitant therapy is initiated, discontinued or if doses are changed.

Warfarin: The protease inhibitor, indinavir, may increase the anticoagulant effect of warfarin.

Zolpidem: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of zolpidem by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zolpidem if indinavir is initiated, discontinued or dose changed.

Zonisamide: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of zonisamide by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zonisamide if indinavir is initiated, discontinued or dose changed.

Zopiclone: Indinavir, a strong CYP3A4 inhibitor, may increase the serum concentration of zopiclone by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zopiclone if indinavir is initiated, discontinued or dose changed.