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

Care should be taken when abacavir is taken with ribavirin, used to treat hepatitis C. Phenytoin, used to treat epilepsy, may also interact with abacavir. If you are taking methadone (used as a heroin substitute), it’s important your doctor is aware of this, as your dose may need to be changed.

Allergic (hypersensitivity) reaction, lactic acidosis (too much lactic acid in the blood). Some, but not all, cohort studies have linked abacavir with an increased risk of heart attack. For this reason, abacavir is not recommended if you have other risk factors for heart disease. Your doctor should discuss this with you.

Nausea, vomiting, diarrhoea, abdominal pain, loss of appetite, fever, headache, tiredness.

Abacavir can cause a serious allergic (hypersensitivity) reaction in people with one particular gene. Before starting treatment with abacavir or any abacavir-containing regimen you should have an HLA-B*5701 test to see if you have this gene. If the test is positive you must not take abacavir. If the test is negative, it is highly unlikely that an allergic reaction will occur, but contact your HIV clinic immediately (or A&E if out of hours) if you begin to feel unwell after starting the drug.

In the box with the drug there is an ‘alert card’, which you should carry with you for the first six weeks of taking abacavir.

The particular side-effects you should look out for during this time are:

• Any skin rash OR

If you get one or more symptoms from at least TWO of the following groups:

• fever
• shortness of breath, sore throat or cough
• nausea or vomiting, or diarrhoea or abdominal pain
• severe tiredness or achiness or generally feeling ill.

You should never retry abacavir, or take any combination containing abacavir, if you have had an allergic reaction to it previously.

Take with or without food.

The usual adult dose of abacavir is 600mg per day, taken as either two 300mg tablets once a day, or one 300mg tablet twice a day. It is available as a generic drug, so its appearance will vary. Abacavir is also available in a combination tablet with lamivudine, and in the single-tablet regimen Triumeq.