What is Norvir?
Norvir is a medicine that contains the active substance ritonavir. It is available as an oral solution (80 mg / ml) and in white capsules (100 mg).
What is Norvir used for?
Norvir is indicated in combination with antiviral medicines to treat patients over two years of age infected with human immunodeficiency virus type 1 (HIV-1), a virus that causes acquired immunodeficiency syndrome (AIDS).
The medicine can only be obtained with a prescription.
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How is Norvir used?
Norvir should be given by a doctor who has experience in the treatment of HIV infection. It should be taken on a full stomach.
Norvir is used in two ways:
- it is used as a 'pharmacokinetic booster' to increase the liver levels of antiviral drugs belonging to the same class as Norvir (protease inhibitors), ie amprenavir, atazanavir, fosamprenavir, lopinavir, saquinavir, tipranavir and darunavir. The standard dose for adults is 100 mg or 200 mg, once or twice a day. The dose depends on the type of associated protease inhibitor. For more information, please refer to the package leaflet attached to the associated drug;
- Norvir can also be used as an antiviral drug. The recommended dose for adults is 600 mg twice a day. For children, the recommended dose depends on the body surface area (calculated using the child's height and weight). Treatment should begin with a reduced dose of the drug, which is gradually increased over 14 days of treatment. For more information, see the package leaflet.
How does Norvir work?
The active substance in Norvir, ritonavir, acts as a pharmacokinetic enhancer by inhibiting the activity of a liver enzyme called CYP3A, which plays a very important role in the metabolism of medicines, including some antivirals. medicines, increases their concentration in the blood and increases their antiviral activity.
At higher doses Norvir acts as a protease inhibitor, meaning it blocks a viral enzyme called protease, which is involved in the reproduction of HIV. If the enzyme is blocked, the virus is unable to reproduce normally, which slows down. the spread of the infection.
Norvir, taken in combination with other antiviral medicines, decreases the amount of HIV in the blood and keeps it at a low level. Norvir does not cure HIV infection or AIDS, but it can delay damage to the immune system and the onset of AIDS-associated infections and diseases.
How has Norvir been studied?
Norvir, as a pharmacokinetic enhancer, has been investigated in clinical trials to evaluate the effect of the antiviral drugs it is intended to potentiate. Information on these studies can be found in the EPARs of these other medicines.
Norvir, as an antiviral drug, has been studied in two main studies involving 1,446 patients. In the first study, Norvir was compared with placebo (a dummy treatment) in 1,090 adults as an add-on to the antiviral drugs already in use by the patient. The main measure of effectiveness was based on the number of patients whose disease got worse or who died. The second study compared Norvir taken alone, zidovudine (another antiviral drug) taken alone, and the combination of Norvir and zidovudine. 356 adults who had not previously received any therapy for HIV infection. The main measure of effectiveness was the change in the level of HIV in the blood (viral load) and in the number of CD4 T cells in the blood (CD4 cell count). CD4 T cells are white blood cells that play an important role in fighting infections and which are killed by HIV. The effects of Norvir as an antiviral drug in combination with other antiviral drugs were also investigated in four studies in children.
What benefit has Norvir shown during the studies?
In the first study of Norvir as an antiviral drug, 16% of cases treated with Norvir (86 out of 543 patients) reported disease worsening or death, compared with 33% of patients treated with placebo (181 out of 547). In the second study, greater reductions in viral load and an increase in CD4 cell counts were seen in patients taking Norvir than in subjects treated with zidovudine alone. The combination of Norvir and zidovudine was less effective than Norvir alone, although the reasons for this are unclear. Norvir in combination with other antiviral drugs also reduced viral loads in children.
What is the risk associated with Norvir?
When Norvir is used as a pharmacokinetic enhancer the side effects depend on the other antiviral drug being taken. Some drugs cannot be taken with Norvir, when used in this way. For further details, see the package leaflet provided with the associated drug.
When Norvir is used as an antiviral drug the most common side effects (seen in more than 1 in 10 patients) are taste alteration (unusual taste in the mouth), perioral and peripheral paraesthesia (disturbed sensation around the mouth or in the hands or feet ), headache, abdominal pain (stomach pain), nausea, diarrhea, vomiting and asthenia (weakness). For the full list of side effects reported with Norvir, see the Package Leaflet.
Norvir must not be used in people who may be hypersensitive (allergic) to ritonavir or any of the other ingredients. It must not be used by patients with severe hepatic impairment or by patients taking the following medicines:
- alfuzosin (used to treat benign prostatic hyperplasia or BPH, enlargement of the prostate gland);
- pethidine, piroxicam, propoxyphene (used for pain relief);
- amiodarone, bepridil, encainide, flecainide, propafenone, quinidine (used to correct cardiac arrhythmia);
- fusidic acid, voriconazole in doses of Norvir of 400 mg two or more times a day, rifabutin when Norvir is used as an antiviral drug (drugs used to treat infections);
- astemizole, terfenadine (commonly used to treat allergy symptoms; these drugs can be purchased without a prescription);
- clozapine, pimozide (used to treat mental illness);
- dihydroergotamine, ergonovine, ergotamine and methylergonovine (used in the treatment of headache);
- cisapride (used to relieve certain stomach problems);
- lovastatin, simvastatin (used to lower blood cholesterol levels);
- sildenafil, when used to treat pulmonary arterial hypertension (high blood pressure in the arteries of the lungs);
- chlorazepate, diazepam, estazolam, flurazepam, midazolam taken orally, triazolam (used to relieve anxiety or sleep disturbances);
- St. John's wort (a herbal preparation used to treat depression).
As with other HIV medicines, patients taking Norvir may be at risk for lipodystrophy (changes in the distribution of body fat), osteonecrosis (death of bone tissue), or immune reactivation syndrome (inflammatory signs and symptoms caused by reactivation of the system immune). Patients with liver problems (including hepatitis B or C) may be at an increased risk of developing liver damage when treated with Norvir.
Why has Norvir been approved?
The Committee for Medicinal Products for Human Use (CHMP) decided that Norvir's benefits in combination with other antiretroviral medicines are greater than its risks in the treatment of HIV-1 infected patients. The committee recommended the granting of a marketing authorization for Norvir. Norvir was initially authorized under "exceptional circumstances" because only limited information was available at the time the authorization was granted, for scientific reasons. As the pharmaceutical company provided the additional information requested, the "in exceptional circumstances" condition lapsed on March 13, 2001.
Other information about Norvir:
On August 26, 1996, the European Commission granted Abbott Laboratories Limited a "Marketing Authorization" for Norvir, valid throughout the European Union. The "Marketing Authorization" is valid indefinitely.
For the full version of Norvir's EPAR click here.
Last update of this summary: 10-2009
Information on Norvir - ritonavir published on this page may be out of date or incomplete. For a correct use of this information, see the Disclaimer and useful information page.
