Drug interactions

Patients taking nelfinavir (Viracept) should not take the following drugs:

  • Alfuzosin
  • Amiodarone (Cordarone X), due to heart problems
  • Astemizole, due to heart problems
  • Cisapride, due to heart problems
  • Colchicine in patients with renal or hepatic impairment
  • Ergotamine tartrate (Cafergot / Migril), due to heart problems
  • Halofantrine
  • Hypericin (St John’s wort), due to decreased nelfinavir levels
  • Lovastatin, due to the risk of lovastatin-associated side-effects
  • Lumefantrine
  • Midazolam (Hypnovel), due to the risk of sedation or breathing problems
  • Quinidine sulphate (Kinidin Dureles), due to heart problems
  • Pimozide (Orap), due to heart problems
  • Rifampicin (Rifadin / Rimactane), due to increased levels of nelfinavir
  • Simvastatin (Zocor), due to simvastatin-associated side-effects1
  • Terfenadine, due to heart problems
  • Triazolam, due to the risk of sedation or breathing problems.

Indinavir (Crixivan), saquinavir (Invirase) and amprenavir (Agenerase) also increase the concentrations of nelfinavir, and vice versa. No dose adjustment is required for amprenavir or saquinavir, but indinavir (Crixivan) should be taken at 1200mg with 1250mg nelfinavir twice a day. Lopinavir levels may also be reduced in people taking ritonavir-boosted lopinavir (Kaletra) with nelfinavir. Measuring drug levels in the blood may be useful.

Efavirenz (Sustiva) can cause elevations in blood nelfinavir levels when it is given with low-dose ritonavir (Norvir).2 Without ritonavir, efavirenz does not affect nelfinavir levels, but there is some evidence that nelfinavir concentrations may begin to fall over time in people who are taking nelfinavir and efavirenz.3 Monitoring drug concentrations to ensure adequate drug exposure may be useful.

A number of other drugs interact with nelfinavir and may require dose adjustements:

  • Atorvastatin (Lipitor) should be used with caution in patients taking nelfinavir.1
  • Carbamazepine (Tegretol) may reduce nelfinavir concentrations and nelfinavir can cause increases in carbamazepine levels, leading to drowsiness and unsteadiness. A dose reduction of 25 to 50% of carbamazepine should be considered, and drug level monitoring used, if possible.4
  • Methadone hydrochloride (Methadose) levels are reduced by nelfinavir, but this does not necessarily cause withdrawal symptoms to develop.5
  • Phenobarbital may reduce nelfinavir concentrations and should be co-administered with caution.
  • Phenytoin (Epanutin) levels may be reduced by nelfinavir. Dose increases may be necessary.
  • Pravastatin sodium (Lipostat) levels are reduced by nelfinavir. A dose increase may be necessary.6
  • Rifabutin (Mycobutin) increases nelfinavir levels, and nelfinavir can decrease rifabutin levels. A reduction of the dose of rifabutin from 300 to 150mg once daily is recommended.
  • Sildenafil (Viagra) levels are increased in patients taking nelfinavir. Sildenafil should be started at a reduced dose of 25mg. Sildenafil is contraindicated if used for treatment of pulmonary arterial hypertension (due to dose required).
  • Tadalafil (Cialis) should be taken at a lower dose in patients taking nelfinavir.
  • Vardenafil (Levitra) should be taken at a lower dose in patients taking nelfinavir.

Levels of the oral contraceptives norethindrone and ethinylestradiol are reduced by nelfinavir, leading to an increased likelihood of pregnancy.7 Alternative methods of contraception are advised.

There is also evidence that levels of the chemotherapy drug combination of adriamycin, cyclophosphamide (Endoxana), vincristine sulphate (Oncovin) and prednisolone (CHOP), used to treat non-Hodgkin’s lymphoma, may be lower than expected in patients taking nelfinavir.8

References

  1. Hsyu PH et al. Pharmacokinetic interactions between nelfinavir and two HMG-CoA reductase inhibitors simvastatin and atorvastatin. 40th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, abstract 425, 2000
  2. la Porte CJL et al. Effect of efavirenz treatment on the pharmacokinetics of nelfinavir boosted by ritonavir in healthy volunteers. Br J Clin Pharmacol 58: 632-640, 2004
  3. Smith PF et al. Pharmacokinetics of nelfinavir and efavirenz in antiretroviral-naive, human immunodeficiency virus-infected subjects when administered alone or in combination with nucleoside analog reverse transcriptase inhibitors. Antimicrob Agents Chemother 49: 3558-3561, 2005
  4. Bates DE et al. Carbamazepine toxicity induced by lopinavir / ritonavir and nelfinavir. Ann Pharmacother 40: 1190-1195, 2006
  5. Hsyu PH et al. Pharmacokinetic interaction of nelfinavir and methadone in intravenous drug users. Biopharm Drug Dispos 27: 61-68, 2006
  6. Aberg JA et al. Pharmacokinetic interaction between nelfinavir and pravastatin in HIV-seronegative volunteers: ACTG Study A5108. AIDS 20: 725-729, 2006
  7. 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
  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
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.