| Potential side effects and toxicity: The most common side effects include: nausea, rash, diarrhea, headache, vomiting, fatigue, mood disorders, abdominal pain, and mouth numbness. Rash occurred in about 19% of patients, but severe rashes were uncommon. If you experience a rash, notify your doctor. For mild or moderate rashes, your doctor may choose to continue Lexiva, with close follow-up and monitoring. Because Lexiva is a sulfonamide, it should be used with caution in patients with allergies to sulfa drugs. Side effects and laboratory abnormalities were similar when Lexiva was taken once or twice daily, with or without Norvir.
As seen with all other protease inhibitors are increased levels of cholesterol and triglycerides, except possibly unboosted Reyataz (atazanavir) and these increased levels may be associated with heart disease. Side effects and laboratory abnormalities were similar when Lexiva was taken once of twice daily, with or without Norvir. Other possible side effects are lipodystrophy (body fat changes, including thinning of the face, arms and legs, with or without fat accumulation in the stomach, breasts and sometimes the upper back), onset of new cases or worsening of diabetes (see your doctor promptly) and increased bleeding in hemophiliacs.
Potential drug interactions: Not recommended to be taken with Kaletra. When taken with Sustiva, boost a once-daily dose of Lexiva with 300 mg of Norvir. There is insufficent data on combining Lexiva, Kaletra and Sustiva—consider using Therapeutic Drug Monitoring (TDM). Like all PIs, do not take with Tambocor (flecainide), Rythmol (propafenone), Versed, Halcion, Hismanol, Seldane, rifampin, ergot derivatives (such as Cafergot, Wigraine and Methergine, D.H.E. 45, in any form—serious interactions seen with dilation during gynecological exams), and the herbal supplement St. John’s wort. Do not use Zocor (simvastatin) or Mevacor (lovastatin); lipid-lowering alternatives are Lipitor (atorvastatin), Lescol, and Pravachol (pravastatin), but they should be used with caution due to potential for liver toxicity. Oral solution contains alcohol, so do not use with Antabuse or Flagyl. Also avoid dihydropuridine calcium channel blockers.
Protease inhibitors increase blood levels of Viagra (sidenafil citrate), Cialis (tadalafil) and Levitra (vardenafil). Use with caution. Initially the Viagra dose should be 12.5 mg (1/2 of 25 mg tablet) and increased as needed and tolerated. It’s recommended that people on PIs do not exceed 25 mg of Viagra in a 48-hour period because of potential for serious reaction. Use Cialis at reduced doses of 10 mg every 72 hours and Levitra at reduced doses of no more than 2.5 mg every 72 hours, with increased monitoring for adverse events.
Tips: Studies have demonstrated that protease inhibitor-experienced patients should take Lexiva 700 mg with Norvir 100 mg, both twice daily. The once daily dosing is not recommended for treatment-experienced patients for whom a PI therapy has previously failed. It is important to take Lexiva exactly as your doctor instructs, and not to change dosing without discussing with your doctor. The FDA points out that the study comparing Lexiva/Norvir against Kaletra in protease inhibitor experienced patients was not large enough to show that the combination was clinically equivalent to Kaletra.
Lexiva is a “pro-drug” formulation of Agenerase. This means that when you take this pill, your body converts it to Agenerase. 700 mg of Lexiva is roughly equivalent to 600 mg of Agenerase. This new formulation is an improvement because it helps to make the pills smaller and easier to swallow. The new formulation also allows the drug to be given with fewer number of pills per day (4 per day). |
Doctor
Lexiva, or fos-amprenavir, is one of the newer PI s, though it is actually a form of amprenavir, or Agenerase. The advantage of Lexiva over its relative is that it can be taken in much smaller quantities: when given unboosted, Agenerase is a mouthful, like unboosted Fortovase. Lexiva can be given unboosted, two pills twice daily; however, most practitioners prefer to boost it with Norvir—one Lexiva plus one Norvir twice daily. Lexiva has a slightly different resistance pattern than some of the other PI s; but like most HIV meds, it’s most effective as a first-line agent, rather than as part of a salvage regimen. It’s hard to see Lexiva’s advantage over Kaletra and boosted Reyataz, though it’s certainly as effective as its competitors. As usual with PI s, diarrhea is the most common side effect.—Ross Slotten, MD |
