Updated February 2010
Norvir – brand name
ritonavir – generic name
Norvir belongs to a class of HIV drugs called protease inhibitors (PIs).
The PIs block protease, a protein that HIV needs to make more copies of itself. This may slow down HIV disease.
The Food and Drug Administration (FDA) has approved Norvir for use in combination with other HIV drugs for the treatment of HIV infection in adults and children over one month old.
Norvir comes in:
- 100 milligram (mg) heat-stable tablets (FDA approved February 2010)
- 100 mg capsules
The full adult dose of Norvir is 600 mg twice a day. However, this dose is very rarely used because of side effects. Norvir is usually used at lower doses (100mg or 200 mg twice a day) in combination with other PIs.
Norvir is one of the two drugs in Kaletra. Kaletra contains the PI lopinavir and small amounts of Norvir.
It is important to take Norvir tablets with food. Norvir capsules can be taken with or without food, but it is better to take them with food.
Norvir should be taken with a meal or light snack.
Check with your child’s health care provider for children’s dosing.
Norvir must be used with other HIV medications to treat HIV.
Tell your health care provider if you have liver problems, diabetes, or hemophilia.
Norvir capsules need to be kept in the refrigerator, but they can also stay out at room temperature (below 77 degrees Fahrenheit, or 25 degrees Celsius) for up to 30 days. The heat-stable tablet formulation can be stored at room temperature and does not require refrigeration.
If you miss a dose of Norvir, take it as soon as possible and then take your next scheduled dose at its regular time. If it is almost time for your next dose, wait and take the next dose at the regular time. Do not double the next dose.
As with all HIV drugs, it is important to take Norvir as prescribed by your health care provider. Missing or skipping doses can cause your blood levels of Norvir to fall too low and the virus can become resistant to it. This may cause Norvir and other HIV drugs you are taking to stop working.
Small doses of Norvir are used to improve or “boost” the effectiveness of other PIs by increasing their levels in your blood. Taking Norvir makes it possible to take a lower dose of the other PIs, which lets you take fewer pills and may result in fewer and less severe side effects.
Norvir in combination with other PIs may be used for people being treated for the first time and for people who are switching from other drugs that no longer work. Norvir may not work as well if your HIV is resistant to certain other PIs.
You and your health care provider should use resistance testing and your treatment history to guide the use of Norvir and to determine which drugs will work best for you.
If your virus develops resistance to Norvir then it may stop working or not work as well for you. You also may not get as much benefit from the other PIs.
Sometimes taking more than one medication can cause drug interactions. This can lead to the drugs not working as well or an increased risk of side effects.
Norvir can interact with other medications. Taking Norvir with certain drugs can change the amount of each drug in your blood. Your health care provider may need to either adjust the doses of your drugs to avoid under- or overdosing or change the drugs you currently take.
Norvir should not be taken with:
- Acid reflux/heartburn medication: Propulsid (cisapride)
- Antibiotics: Priftin (rifapentine) and Rifadin (rifampin)
- Antifungal: Vfend (voriconazole)
- Antimigraine medications: Methergine, Methylergometrine (methylergonovine); Ergostat, Cafergot, Ercaf, Wigraine (ergotamine); Ergotrate, Methergine (ergonovine); or D.H.E. 45, Migranal (dihydroergotamine)
- Antihistamines: Hismanal (astemizole) or Seldane (terfenadine)
- Heart medications: Cordarone (amiodarone), Vascor (bepridil), Tambocor (flecainide), Rythmol (propafenone), or Quinaglute/Quinidex (quinidine)
- Cholesterol-lowering drugs (statins): Zocor (simvastatin) and Mevacor (lovastatin)
- Antipsychotic: Orap (pimozide)
- Sedatives: Versed (midazolam) and Halcion (triazolam)
- Enlarged prostate drug: Uroxatral (alfuzosin)
- Herbal product: St. John's wort
- Medication used for the treatment of pulmonary arterial hypertension: Revatio (sildenafil)
If you are taking any of the following medications with Norvir, speak to your health care provider as your doses may need to be adjusted:
- Anticonvulsants: Tegretol (carbamazepine), Luminal (phenobarbital), Dilantin (phenytoin)
- Painkiller: Demerol (meperidine)
- Anti-depressant: Norpramin (desipramine)
- Medications used to treat TB, MAC, and other bacterial infections: Mycobutin (rifabutin) and Biaxin (clarithromycin)
- Erectile dysfunction drugs: Viagra (sildenafil), Levitra (vardenafil), Cialis (tadalafil)
- Medication used to treat thrush (candidiasis) and other fungal infections: Nizoral (ketoconazole)
- Medications used to treat asthma, bronchitis, or emphysema: theophylline,
inhaled medicines such as salmeterol (Severent), salmeterol in combination with
fluticasone propionate (Advair), or fluticasone propionate (Flonase)
People taking liquid Norvir should not take Antabuse (disulfiram) or Flagyl (metronidazole).
Methadone levels in the bloodstream can decrease when combined with Norvir. Because of this, it might be necessary to increase the dose of methadone.
Norvir decreases the effectiveness of birth control pills, so alternative birth control methods should be used.
When using Norvir with other PIs, check drug interactions for the other PI
as well as interactions for Norvir.
Because there are so many possible drug interactions with Norvir, it is very important to go over all your medications with your health care provider. Be sure your health care provider knows about all the medications you are taking (including over-the-counter, prescription, street drugs, and herbs), even if you only use them occasionally.
For more information and additional resources to check interactions between
the particular drugs you are taking, see our info sheet on
drug interactions or go to:
It is not uncommon to experience Norvir side effects. However, they are likely to be temporary and go away as your body adjusts to the medication. If you experience any of the side effects listed below, call your health care provider for advice. Do not just stop taking your medication.
- Abdominal pain
- Intestinal gas (flatulence)
- Loss of appetite
- Changes in taste
- Fatigue (unusual tiredness)
- Insomnia (inability to sleep)
- Tingling or numbness around the mouth (oral paresthesia)
More serious side effects:
- According to a February 2010 FDA announcement, taking Invirase plus Norvir may increase your risk for developing abnormal heart rhythms. In some cases this could lead to serious heart problems, including a condition called torsades de pointes (dangerous and irregular heart beat) and heart block (slowing of the heart beat). These problems can be seen on a test called an electrocardiogram (EKG). Symptoms include lightheadedness, fainting, or abnormal heart beats. The FDA is investigating to see if there is definite link between the use of Invirase plus Norvir and these heart problems. In the meantime, Invirase plus Norvir should not be used by people taking heart medications including quinidine, amiodarone, or antiarrhythmic drugs; or in people with a history of these types of heart conditions. The FDA suggests that people using Invirase plus Norvir speak with their health care providers about their cardiovascular (heart) history and current medications to determine if they should continue using Invirase plus Norvir.
- Liver toxicity: this may be indicated by elevated liver enzymes or yellowing of the skin and eyes (jaundice). People with liver diseases such as hepatitis B and C may have worsening liver problems.
- Pancreatitis (problems with your pancreas): tell your health care provider if you have nausea, vomiting, or abdominal pain.
- High blood sugar (hyperglycemia), diabetes, or worsening of diabetes may occur.
- Increased bleeding problems in some HIV+ people with hemophilia.
- Lipodystrophy, which may include elevated blood sugar (glucose), elevated lipid levels ( cholesterol and triglycerides), and fat gain or loss in certain areas. Norvir can cause significant increases in lipid levels. The exact causes of lipodystrophy are not known, but may include HIV and/or HIV drugs. It is unclear if Norvir will cause or impact other symptoms of lipodystrophy. For more information on lipodystrophy, see our info sheet.
If you are experiencing persistent, unusual, or serious side effects, call your health care provider right away.
As one of the earliest PIs, Norvir has been studied in many women. Studies of Norvir pharmacokinetics (how the drug is processed by the body) show that the drug behaves similarly in the bodies of women and men.
In study 247, participants had Norvir or a placebo (sugar pill) added to their current nucleoside reverse transcriptase inhibitor drug regimen. This study included about 8 percent (or 91) women out of 1,090 total participants. People who took Norvir achieved lower viral loads, had increased CD4 cell counts, and were about half as likely to experience AIDS progression or death.
Study 245 found that Norvir plus Retrovir (zidovudine or AZT) worked better than Norvir alone (monotherapy), which in turn worked better than Retrovir alone. Another study of 62 people (including two women) also found that Norvir monotherapy reduced viral load and increased CD4 cell counts. (From later studies, we know now that Norvir should not be used alone.)
Some research suggests that women may be more likely than men to experience side effects when taking Norvir. One study found that 66 percent of women (23 out of 35) developed side effects, compared with 27 percent of men (14 out of 52). The researchers attributed this difference to higher drug levels in women.
Another study that included 90 women and 996 men also found more side effects in women.
Women were more likely to experience:
- Nausea – 65 percent of women versus 56 percent of men
- Vomiting – 49 percent of women versus 31 percent men
- Aches and fatigue – 47 percent of women versus 34 percent of men
- Numbness and tingling around the mouth - 37 percent of women versus 27 percent of men
Men were more likely to experience:
- Diarrhea – 64 percent versus 49 percent of women
A researcher also reported on four women who developed anemia (low red blood cells) after having very heavy menstrual periods after starting Norvir (none of the women had heavy periods before).
In addition, some studies suggest that the metabolic side effects (lipodystrophy) associated with PIs may be somewhat different in women and men. However, it is still unclear if women are more likely to gain or lose body fat in certain areas than men.
Studies have shown that pregnant women who use HIV drugs can greatly reduce the risk of passing HIV on to their babies. There have been no formal studies on the use of Norvir during pregnancy.
An Antiretroviral Pregnancy Registry has been established to collect information on pregnant women who take HIV drugs, including Norvir. If you are pregnant and taking Norvir or other HIV drugs, your health care provider can register you by calling 1-800-258-4263 or going to www.apregistry.com.
It is not known whether Norvir passes into breast milk. HIV+ women should not breast-feed because their babies could be infected with HIV through the breast milk.
Check with your health care provider about the best treatment options for you and your baby if you are thinking of getting pregnant.
Click this link for more information about pregnancy.
People who are starting HIV treatment for the first time may develop Immune Reconstitution Syndrome or IRS (also called Immune Reconstitution Inflammatory Syndrome or IRIS). IRS can happen as a result of the immune system getting stronger and responding to an HIV-related infection such as Mycobacterium avium infection (MAC), cytomegalovirus (CMV), Pneumocystis jirovecii pneumonia (PCP), or tuberculosis (TB). People may have been treated for these infections in the past or not even know they have them. If you notice any unusual symptoms soon after starting HIV drugs for the first time, let your health care provider know right away so you can be evaluated and, if necessary, treated.