Types of side-effects

There are two main reasons for side-effects: an allergic reaction to the drug which causes side-effects, or side-effects caused by the direct effects of a medicine.

An allergic reaction will cause side-effects such as a rash or fever. You should contact your doctor immediately if you suspect that you have developed an allergic reaction to any medicine you are taking.

An allergic (hypersensitivity) reaction to abacavir (Ziagen, also combined with 3TC in Kivexa and AZT and 3TC in Trizivir) can be potentially fatal. If you are taking abacavir you should read carefully the warning card that comes with boxes of the medicines and contact your doctor immediately if you experience any symptoms suggesting that you might be experiencing an allergic reaction to the drug.

A hypersensitivity reaction can also occur in people taking nevirapine (Viramune) consisting of severe rash and liver toxicities. Because of this, men with a CD4 cell count of 400 or above, and women with a CD4 cell count of 250 or more, should not start taking HIV treatment for the first time with nevirapine.

If a side-effect is being caused by the unwanted effects of a drug itself, the nature of the side-effect might depend on which part of the body the drug is intended to treat, or the way in which the body processes the drug. For example, some drugs can damage the cells in bone marrow which are responsible for producing new blood cells, so this could mean that your body doesn’t produce enough red or white blood cells. Some medicines can make you feel generally unwell, or cause vomiting, nausea, or diarrhoea. Reduced sex drive or sexual problems are another common side-effect.

Side-effects are often related to the amount of drug you are taking – for some drugs, but not all, it is possible to adjust the dose you receive to help minimise the risk of side-effects.