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) capsules
• Liquid

The full adult dose of Norvir is six 100 mg capsules twice a day.

Norvir is usually used at lower doses (one or two 100mg capsules twice a day) in combination with other PIs.

If Norvir is the only PI used, people usually start with a low dose that is gradually increased in order to reduce side effects.

Norvir should be taken with meals.

Check with your child’s doctor for children’s dosing.

Norvir must be used with other HIV medications to treat HIV.

Tell your doctor if you have liver problems, diabetes, or hemophilia.

You should keep Norvir capsules in your refrigerator, but they can also stay out at room temperature (below 77 degrees Fahrenheit, or 25 degrees Celsius) for up to 30 days. The liquid version should not be refrigerated.

As with all HIV drugs, it is important to take Norvir as prescribed. Missing or skipping doses can cause your blood levels of the drug to fall too low and resistance can develop. When your virus becomes resistant to an HIV medication, that drug may stop working.

Norvir improves or “boosts” the effectiveness of some 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 may be used for people being treated for the first time.

Norvir may be used for people who are switching from other drugs that no longer work, since Norvir is primarily used to increase blood levels of other PIs. If Norvir is being used as the primary PI, it may not work as well if HIV is resistant to certain other PIs.

Your doctor can run a resistance test to help determine whether Norvir is likely to work 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. Because of the way Norvir is metabolized, or processed in the body, it interacts with many drugs including drugs for conditions other than HIV. Make sure your doctor or pharmacist checks the list of drug interactions anytime you are prescribed new medicines.

Taking certain drugs (including methadone, some antifungals, antidepressants, painkillers, drugs for lung problems, TB drugs, other HIV drugs, drugs to treat erectile dysfunction such as Viagra, and cholesterol-lowering drugs) with Norvir can change the amount of each drug in your blood. Your doctor may need to adjust the doses of your drugs to avoid under- or overdosing.

Norvir decreases the effectiveness of birth control pills, so alternative birth control methods should be used.

Certain medications (including some antihistamines, acid reflux/heartburn drugs, antibiotics, sedatives, migraine medications, calcium channel blockers, antipsychotics, and other PIs and heart medications) should not be taken with Norvir. Do not take St. John’s wort with Norvir either.

People taking liquid Norvir should not take Antabuse (disulfiram) or Flagyl (metronidazole).

Be sure your doctor 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.

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 doctor for advice. Do not just stop taking your medication.

• Nausea
• Diarrhea
• Abdominal pain
• Intestinal gas (flatulence)
• Loss of appetite
• Heartburn
• Headaches
• Fatigue (unusual tiredness)
• Weakness
• Insomnia (inability to sleep)
• Tingling or numbness around the mouth (oral paresthesia)

More serious side effects:

• Liver toxicity: this may be indicated by elevated liver enzymes or yellowing of the skin and eyes (jaundice). Liver problems are more common with Norvir than with other protease inhibitors.
• 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 doctor right away.

As one of the earliest protease inhibitors, 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 is not a lot of information about the use of Norvir during pregnancy.

Check with your doctor 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 doctor know right away so you can be evaluated and, if necessary, treated.

1		Gatti, C, et. al. (1999). Gender as a risk factor for ritonavir intolerance. 39th Interscience Conference on Antimicrobial Agents and Chemotherapy. San Francisco, CA.Abstract I238.
2		Markowitz, M, et. al. (1995). A preliminary study of ritonavir, an inhibitor of HIV-1 protease, to treat HIV-1 infection. New EnglandJournal of Medicine, 333(23). 1534.
3		Melbourne, K, et. al. (1998). Tolerability and body composition of HIV-infected individuals on ritonavir-containing regimens. 38th Interscience Conference on Antimicrobial and Antiviral Chemotherapy. San Diego, CA. Abstract I-89.
4		Nielsen, H. (1999). Hypermenorrhoea associated with ritonavir. The Lancet, 353(9155). 811-812.