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ritonavir (Norvir)
Ritonavir (trade name Norvir) is one of a class of anti-HIV drugs called protease inhibitors. These drugs work by blocking a part of HIV called protease. When protease is blocked, HIV makes copies of itself that can't infect new cells. Anti-HIV drug combinations, sometimes called cocktails, can reduce the amount of HIV in your body.
Taking the drug: The standard dose of ritonavir is 600 mg taken twice a day. When combined with the protease inhibitor saquinavir (Fortovase) the dose is 400 mg twice a day (see below). To try and reduce side effects, the drug's manufacturer recommends building up the dose of ritonavir slowly over a few days. It is very important that you take no more than 14 days to build up the dose, as this could help HIV get resistant to the effects of the drug.
Ritonavir should also be taken with a full high-protein, high-fat meal if possible. Some doctors suggest that taking ritonavir right after a meal with yogurt may help reduce side effects. The liquid form of ritonavir has very bad taste, but there are some tips for getting around this problem. Suggestions include: Drinking the liquid through a straw so it goes straight down your throat without being tasted, mixing the liquid with chocolate milk or nutritional supplement, coating the tongue with peanut butter or sucking popsicles beforehand to numb the taste buds.
Side effects: The major side effects seen in ritonavir studies were nausea, vomiting, weakness and diarrhea. Other side effects that have been associated with the drug are numbing sensations around the mouth and elevated liver enzymes. Anyone taking a protease inhibitor should have their liver function closely monitored. People that have hepatitis are at greater risk for getting elevated liver function tests when taking protease inhibitors. Your doctor should test for hepatitis infections before starting a protease inhibitor.
Some people taking combination anti-HIV drugs are also experiencing swollen bellies, and losing fat from their face, arms and legs. The general name given to this syndrome is lipodystrophy. Doctors aren't sure what's causing this problem, and studies are underway to try and find out. Tell your doctor if you experience these symptoms while taking ritonavir.
Protease inhibitor combinations: When taken together, ritonavir increases the amount of the protease inhibitor saquinavir (Fortovase) in the body. Because the level is higher than usual, the dose of both drugs is lowered. When taken together, the doses are 400 mg of Fortovase and 400 mg of ritonavir twice a day. This combination, along with one or two nucleoside analog drugs (AZT, ddI, ddC, d4T, 3TC) is listed as a possible first HIV treatment in the new Public Health Service guidelines on how to use HIV drugs. Other studies are now investigating lower doses of ritonavir taken with saquinavir, and a once-daily combination of these two drugs. Several other studies are investigating low doses of ritonavir in combination with the protease inhibitors indinavir (Crixivan) and amprenavir (Agenerase).
Drug interactions: Ritonavir can effect the way other drugs are absorbed by the body. It is very important that anyone about to start taking ritonavir goes over all the medications they are taking with their healthcare provider. Many of the drug interactions are potentially life-threatening. If you need help working out which drugs are on the interaction list (some drugs have several different names) call The Network. Not all protease inhibitors interact with as many other drugs. You may also be able to switch a problem drug so that you can take ritonavir. A recent study has shown that ritonavir lowers methadone levels, so people taking this combination should be monitored for signs of withdrawal. A dose increase of methadone may be necessary in some cases.
These are the drugs that should NOT be co-administered with ritonavir: amiodarone, astemizole, bepridil, cisapride, flecainide, midazolam, propafenone, pimozide, quinidine, terfenadine, triazolam and a class of migraine drugs called ergot derivatives. Abbott has set up a special information line for people needing more information on prescribing ritonavir - the number to call is (800) 441-4987.
Warnings: There has been a government warning about protease inhibitors causing high blood sugar and diabetes. Symptoms to watch out for include increased thirst and hunger, unexplained weight loss, increased urination, fatigue, and dry, itchy skin. In the cases of this problem reported so far, symptoms usually began 10-11 weeks after starting the protease inhibitor, although in one case symptoms started just four days afterwards. There are also reports of protease inhibitors causing high levels of fats (called cholesterol and triglycerides) in the blood. Because this can lead to heart problems, fat levels should be closely monitored in people taking protease inhibitors.
Storage: Refrigeration of liquid ritonavir is no longer recommended, but avoid exposing liquid ritonavir liquid to severe heat or cold. The new soft gelatin ritonavir capsules should be stored in a refrigerator if possible. However, refrigeration is not required if the capsules are used within 30 days and kept below 77 degrees Fahrenheit.
Abbott Laboratories, the makers of ritonavir, have set up a patient assistance program for people having difficulty paying for the drug. Call (800) 659-9050 for more information.