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 certain 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 amprenavir (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
Fos-amprenavir is a new formulation of an older protease inhibitor, amprenavir (Agenerase). This newer formulation allows for much better absorption and therefore fewer pills per day. It may be given with or without a boosting dose of ritonavir. It may be given without regard to food, and can be dosed once or twice daily in treatment naïve patients. In PI-experienced patients, it should only be used twice-daily. Clinical trials suggest that when given with a booster dose of ritonavir, it is nearly as potent as Kaletra. As with Reyataz, durability and resistance data are lacking only because the drug has not been available in clinical trials as long as Kaletra. As with other PIs, its main side effect is diarrhea. It may also lead to elevated total cholesterol and triglyceride levels. Due to its predicted resistance profile, Lexiva is usually considered a first-line agent rather than used in salvage. Simultaneous use with Kaletra is tricky due to a complex interaction between the drugs; this combination is not used commonly.—Chad J. Zawitz, MD
Activist
It was hard to say anything about Lexiva. It is a second generation Agenerase with fewer side effects and lower pill count. It has not gained the acceptance that Reyataz and Kaletra have gained in the market. It has interactions with Kaletra and Sustiva. I took it with Norvir for a few months, but had to stop it due to severe fatigue, a side effect not usually reported with this PI (we are all very different in how we respond to meds). But many people are taking it successfully and like its lower incidence of GI side effects and lipids. It can be used with or without Norvir. It can cause rash in some patients, especially if you are allergic to sulfa drugs, such as Bactrim.—Nelson Vergel
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