What are side effects?
Side effects are usually the unwanted things that a medicine does, which can be annoying, difficult and in rare cases, extremely serious.
Side effects are also called adverse events or referred to as drug toxicity.
Drugs are licensed to treat a specific illness. Anything else it does is called a side effect. Sometimes side effects can be helpful, but more often they are a problem.
In this guide we mainly focus on unwanted effects of HIV antiretroviral drugs (ARVs).
Do all drugs have side effects?
Every drug has side effects. In most cases these will be mild and easy to manage.
Sometimes they are so mild that they are not noticed. They usually only affect a small proportion of people.
When more serious side effects are possible, they usually occur more rarely.
How common are side effects with HIV drugs?
Most HIV drugs are very safe, even when the information about side effects sounds worrying.
Many common over-the-counter medicines like aspirin or paracetamol have similar potential side effects (see Table 1).
Not everyone taking drugs will have the same effects. What is important is how they affect you and what you can do about them.
Most people starting HIV treatment report one or more side effects.
Sometimes this is because when you start a treatment you are more sensitive to anything that happens, even though it may not be a side effect.
Some placebo studies (where there is no active drug) also report 90% side effects.
Table 1: Side effects listed for aspirin
| Dyspepsia (digestive problems), nausea, vomiting. Less commonly, irritation of the gastrointestinal mucosa may lead to erosion, ulceration, gastrointestinal bleeding. Hepatotoxicity (liver toxicity), which occurs rarely. |
| Hypersensitivity reactions including urticaria (rash), rhinitis (nasal problems), angioedema and severe bronchospasm (blocked airways). |
| May cause salt and water retention as well as a deterioration in kidney function. |
Symptoms vs side effects
The word symptom is usually used for any change in how you feel that you could report to your doctor. For example, feeling tired, or having diarrhoea are both symptoms that could be side effects.
Other side effects can only be picked up by a lab test, for example, high cholesterol or raised liver enzymes.
The symptoms of many common side effects are similar to symptoms of illnesses.
Your doctor needs to know about every symptom in order to be able to decide whether it is caused by treatment (a side effect) or a different illness.
Different treatments are needed when a symptom relates to an illness.