Nevirapine may be marketed under the name Viramune, but generic versions are also available. It is taken in combination with other antiretroviral drugs.

You should not take nevirapine with St John's wort.

Some drugs interact with nevirapine and change blood levels of the drugs, which may stop them working or cause side-effects. These include the antiretroviral drugs atazanavir, lopinavir/ritonavir (Kaletra) and efavirenz.

It’s also particularly important your doctor knows if you are taking any of the following drugs with nevirapine, so that the effects can be monitored: antibiotics used to treat certain infections, such as TB (including rifampicin, rifabutin and clarithromycin), anti-fungal treatments, methadone and warfarin.

Nevirapine may reduce the effectiveness of hormonal contraceptives (such as the pill, patches or an implant). If you are using this type of contraceptive to prevent pregnancy you should use an additional or different type of contraception.

Resistance to nevirapine is likely to cause resistance to efavirenz and possibly to rilpivirine.

Severe rash (Stevens-Johnson syndrome).

Allergic (hypersensitivity) reaction, headache, rash (usually in the first six weeks of treatment), fatigue, abdominal pain, diarrhoea, nausea, vomiting, fever, raised liver enzymes and high blood pressure.

Nevirapine can cause a serious hypersensitivity (allergic) reaction in some people. This is more likely in the first 18 weeks of treatment, and especially in the first 6 weeks of treatment, so your doctor will monitor you more closely than usual during this time. The reaction is more likely in people who have higher CD4 counts when they start taking nevirapine.

The symptoms of the reaction are a rash, along with other symptoms which may include: fever, blisters, sores in the mouth, eye inflammation, facial or other swelling, difficulty breathing, muscle or joint pain, generally feeling ill.

Another possible serious reaction affects the liver. Symptoms of liver problems include yellowing of the skin or whites of the eyes (jaundice), dark or tea-coloured urine, pale-coloured stools, nausea, vomiting, loss of appetite and pain, aching or sensitivity on the right side of your body.

If you experience symptoms of an allergic reaction or liver problems you should contact a doctor immediately (either your HIV clinic or A&E if your clinic is closed).

You should never retry nevirapine, if you have had an allergic reaction to it previously.

Take with or without food. Prolonged-release nevirapine must be swallowed whole and not crushed, chewed or divided.

The usual adult dose is one 200mg tablet taken once a day for the first two weeks and then one 200mg tablet twice a day thereafter. Alternatively, you may be prescribed one 400mg tablet of prolonged-release nevirapine after the first two weeks of taking the 200mg dose.

Men should not start treatment with nevirapine if their CD4 cell count is above 400 and women should not start treatment with nevirapine if their CD4 cell count is above 250, as this increases the risk of potentially dangerous side-effects relating to the liver.

Nevirapine is available as a generic drug so appearances will vary.