Drug interactions

A number of drugs should be avoided by patients taking indinavir (Crixivan), due to dangerous interactions, including:

  • Alfuzosin
  • Alprazolam (Xanax)
  • Amiodarone hydrochloride (Cordarone X), due to an increased risk of irregular heartbeat
  • Astemizole, due to an increased risk of irregular heartbeat
  • Atazanavir (Reyataz)
  • Cisapride, due to an increased risk of irregular heartbeat
  • Colchicine in patients with renal or hepatic impairment
  • Ergotamine tartrate (Cafergot / Migril)
  • Flecainide acetate (Tambocor)
  • Halofantrine
  • Hypericin (St John’s wort), due to reduced indinavir levels1
  • Lovastatin
  • Lumefantrine
  • Midazolam (Hypnovel)
  • Pimozide (Orap), due to an increased risk of irregular heartbeat
  • Quinidine sulphate (Kinidin Dureles), due to an increased risk of irregular heartbeat
  • Rifampicin (Rifadin / Rimactane)2
  • Simvastatin (Zocor)
  • Terfenadine, due to an increased risk of irregular heartbeat
  • Triazolam
  • Vardenafil (Levitra).

Indinavir interacts with some other anti-HIV drugs and dose adjustments are required:

  • People taking ddI (didanosine, Videx) tablets should take them on an empty stomach one hour before or one hour after taking indinavir.3 However, people taking enteric-coated ddI capsules (VidexEC) can take them at the same time as indinavir.
  • When combined with efavirenz (Sustiva), levels of indinavir fall. A dose increase to 1000mg indinavir every eight hours is advised, although this may increase side-effects. Concentrations of ritonavir (Norvir) are also lowered by efavirenz, so when ritonavir-boosted indinavir is taken with efavirenz, a dose adjustment to 800mg indinavir and 200mg ritonavir twice daily may be required. Monitoring the level of indinavir in the blood may be useful.4
  • When combined with nevirapine (Viramune), levels of indinavir fall, requiring an increase in dosing to 1000mg every eight hours.
  • Saquinavir (Invirase) and indinavir should be taken together cautiously.

Many other drugs and complementary therapies interact with indinavir, and may require dose adjustments, or use with caution. These include:

  • Amlodipine (Istin) levels may be increased by indinavir. It should be started at a low dose.5
  • Atorvastatin (Lipitor) levels may be increased by indinavir. It should be used with caution.
  • Diltiazem hydrochloride (Tildiem / Adizem-SR / Adizem-XL / Angitil SR / Angitil XL / Calcicard CR / Dilcardia SR / Dilzem SR / Dilzem XL / Slozem / Tildiem LA / Tildiem Retard / Viazem XL / Zemtard) levels may be increased by indinavir. It should be started at a low dose.5
  • Itraconazole (Sporanox) increases indinavir concentrations: a dose of 600mg indinavie three times daily is recommended.
  • Ketoconzaole (Nizoral) increases indinavir concentrations: a dose of 600mg indinavie three times daily is recommended.
  • Rifabutin (Mycobutin) concentrations are increased by indinavir, and indinavir concentrations are reduced by rifabutin. It is recommended that the dose of rifabutin is reduced by half and the dose of unboosted indinavir is increased to 1000 or 1200mg three times a day.
  • Sildenafil (Viagra) levels are increased by indinavir, increasing the risk of side-effects. Patients taking indinavir should start with a reduced dose of 12.5mg sildenafil.6 Sildenafil is contraindicated if used for treatment of pulmonary arterial hypertension, due to dose required.
  • Tadalafil (Cialis) levels are increased by indinavir, increasing the risk of side-effects. Patients taking indinavir should half the recommended dose of tadalafil.

  • Venlafaxine (Efexor / Efexor XL), an antidepressant that reduces indinavir levels.7

Chemotherapy for non-Hodgkin’s lymphoma consisting of adriamycin, cyclophosphamide (Endoxana), vincristine sulphate (Oncovin) and prednisolone (CHOP) can cause a reduction in indinavir levels. Testing of drug levels in the blood is recommended.8

In contrast to most protease inhibitors, indinavir increases the levels of the oral contraceptives norethindrone by 26% and ethinylestradiol by 24%. This can enhance their contraceptive activity.9

Garlic supplements have been shown to reduce blood levels of saquinavir by half, but it is not known if they have the same effect on indinavir levels. Caution should be exercised, especially if indinavir is not being boosted with ritonavir. Taking 1g or more of vitamin C a day has also been shown to reduce indinavir concentrations by 20% in healthy volunteers.10

References

  1. Piscitelli SC et al. Indinavir concentrations and St John's wort. Lancet 355: 547-548, 2000
  2. Justesen US et al. Pharmacokinetic interaction between rifampin and the combination of indinavir and low-dose ritonavir in HIV-infected patients. Clin Infect Dis 38: 426-429, 2004
  3. Shelton MJ et al. If taken 1 hour before indinavir (IDV), didanosine does not affect IDV exposure, despite persistent buffering effects. Antimicrob Agents Chemother 45: 298-300, 2001
  4. Aarnoutse R et al. The influence of efavirenz on the pharmacokinetics of a twice-daily combination of indinavir and low-dose ritonavir in healthy volunteers. Clin Pharmacol Ther 71: 57-67, 2002
  5. Glesby MJ et al. Pharmacokinetic interactions between indinavir polus ritonavir and calcium channel blockers. Clin Pharmacol Ther 78: 143-153, 2005
  6. Merry C et al. Interaction of sildenafil and indinavir when co-administered to HIV-positive patients. AIDS 13: 101-107, 1999
  7. Levin GM et al. A pharmacokinetic drug-drug interaction study of venlafaxine and indinavir. Psychopharmacol Bull 35: 62-71, 2001
  8. Cruciani M et al. Pharmacokinetic interaction between chemotherapy for non-Hodgkin's lymphoma and protease inhibitors in HIV-1-infected patients. J Antimicrob Chemother 55: 546-549, 2005
  9. Clark RA et al. Population-based study evaluating association between selected antiretroviral therapies and potential oral contraceptive failure. J Acquir Immune Defic Syndr 37: 1219-1220, 2004
  10. Slain D et al. Effect of high-dose vitamin C on the steady-state pharmacokinetics of the protease inhibitor indinavir in healthy volunteers. Pharmacotherapy 25: 165-170, 2005
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.