Norvir is a medicine that contains the active substance ritonavir. It is available as an oral solution (80 mg/ml), white capsules (100 mg) and white, oval tablets (100 mg).
|Table of Contents|
|What is it used for?|
|How is it used?|
|How does it work?|
|How has it been studied?|
|What benefits has it shown during the studies?|
|What is the risk associated?|
|Why has it been approved?|
Norvir is used in combination with antiviral medicines to treat patients over two years of age who are infected with human immunodeficiency virus type 1 (HIV-1), a virus that causes acquired immune deficiency syndrome (AIDS).
The medicine can only be obtained with a prescription.
Treatment with Norvir should be given by a doctor who has experience in the treatment of HIV infection. It must be taken with food.
Norvir is used as a ?pharmacokinetic enhancer? (booster) to increase the blood levels of antiviral medicines that belong to the same group as Norvir (protease inhibitors), i.e. amprenavir, atazanavir, fosamprenavir, lopinavir, saquinavir, tipranavir and darunavir. The standard dose for adults is 100 or 200 mg, once or twice a day. The dose depends on which other protease inhibitor is being taken. For more information, see the Package Leaflet provided with the other medicine.
Norvir can also be used as an antiviral medicine. The recommended dose for adults (aged 18 years or over) is 600 mg twice a day. For younger patients, the recommended dose depends on the body surface area (calculated using the patient?s height and weight). Treatment should start with a low dose that is gradually increased over the first 14 days of treatment.
The active substance in Norvir, ritonavir, works as a pharmacokinetic enhancer by blocking the activity of a liver enzyme called CYP3A. This enzyme is very important in the breakdown of medicines, including some antiviral medicines. By slowing down the rate at which these medicines are broken down, it can increase their levels in the blood and increase their antiviral activity. At higher doses, Norvir works as a ?protease inhibitor?. This means that it blocks a viral enzyme called protease, which is involved in the reproduction of HIV. When the enzyme is blocked, the virus does not reproduce normally, slowing down the spread of infection. Norvir, taken in combination with other antiviral medicines, reduces the amount of HIV in the blood and keeps it at a low level. Norvir does not cure HIV infection or AIDS, but it may delay the damage to the immune system and the development of infections and diseases associated with AIDS.
Norvir has been studied as a pharmacokinetic enhancer in clinical studies that were designed to assess the effects of the antiviral medicines that it is used to boost. Information on these studies can be found in the EPARs for the other medicines.
The capsules and oral solution have been studied as an antiviral medicine in two main studies involving 1,446 patients. The first compared Norvir with placebo (a dummy treatment) in 1,090 adults, as an add-on to the antiviral medicines the patients were already taking. 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 medicine) taken alone and the combination of Norvir and zidovudine in 356 adults who had not taken treatment for HIV infection before. The main measure of effectiveness was the change in the levels of HIV in the blood (viral load) and CD4 T-cell levels in the blood (CD4 cell count). CD4 T-cells are white blood cells that are important in helping to fight infections, but which are killed by HIV. The effects of Norvir as an antiviral medicine in combination with other antiviral medicines were also studied in four studies of children.
The company also carried out additional studies showing that the tablets are treated by the body in a comparable way to the capsules.
In the first study of Norvir as an antiviral medicine, 16% of the Norvir-treated patients (86 out of 543) experienced a worsening of disease or died, compared with 33% of the patients taking placebo (181 out of 547). In the second study, patients taking Norvir had greater reductions in viral load and increases in CD4 cell counts than those taking zidovudine alone. The combination of Norvir and zidovudine was less effective than Norvir alone, although the reasons for this were unclear. Norvir, in combination with other antiviral medicines, also reduced viral loads in children.
What is the risk associated with Norvir When it is used as a pharmacokinetic enhancer, the side effects of Norvir depend on the other antiviral medicine being taken. Some medicines cannot be taken with Norvir when it is used in this way. See the Package Leaflet provided with the other medicine for full details. When it is used as an antiviral medicine, the most common side effects with Norvir seen in more than 1 patient in 10 are taste perversion an altered sense of taste, circumoral and peripheral paraesthesia abnormal sensations around the mouth, or in the hands or feet, headache, abdominal pain stomach ache, nausea feeling sick, diarrhoea, vomiting and asthenia weakness. For the full list of all side effects reported with Norvir, see the Package Leaflet. Norvir should not be used in people who may be hypersensitive allergic to ritonavir or any of the other ingredients. It must not be used in patients who have severe problems with their liver or who are taking any of the following medicines alfuzosin used to treat benign prostatic hyperplasia or BPH, an enlarged prostate gland pethidine, piroxicam, propoxyphene used to relieve pain amiodarone, bepridil, encainide, flecainide, propafenone, quinidine used to correct irregular heartbeat fusidic acid, voriconazole at Norvir doses of 400 mg twice a day or more, rifabutin when Norvir is used as an antiviral medicine medicines used to treat infections astemizole, terfenadine commonly used to treat allergy symptoms - these medicines may be available without a prescription clozapine, pimozide used to treat mental illness dihydroergotamine, ergonovine, ergotamine, methylergonovine used to treat migraine headache cisapride used to relieve certain stomach problems lovastatin, simvastatin used to lower cholesterol in the blood sildenafil when used to treat pulmonary arterial hypertension high blood pressure in the arteries of the lungs
- clorazepate, diazepam, estazolam, flurazepam, midazolam taken by mouth, triazolam (used to relieve anxiety or difficulty sleeping);
- St John?s wort (a herbal preparation used to treat depression).
As with other anti-HIV medicines, patients taking Norvir may be at risk of lipodystrophy (changes in the distribution of body fat), osteonecrosis (death of bone tissue) or immune reactivation syndrome (symptoms of infection caused by the recovering immune system). Patients who have problems with their liver (including hepatitis B or C infection) may be at an elevated risk of liver damage when taking Norvir.