Medication side effects - what are they?

The body is a complex structure in which chemicals work together to regulate everything from our bone growth to our body temperature.

Hormones, enzymes and the brain's messenger chemicals continually regulate endless bodily processes to keep the body in its "steady state". This allows the body to function well or to respond to situations such as cold or exertion. Each enzyme, hormone or chemical messenger involved in regulating the body may have more than one function.

When this balance is lost we might develop symptoms. Sometimes these will signal an underlying disease. Medical treatments are often aimed at helping to restore the balance or to compensate for the imbalance.

Most prescription and non-prescription medicines, complementary and alternative medicines, and dietary supplements have both good and bad effects. The good effects will usually be the desired effects, related to the reason you are taking the product, while the bad effects are the side effects (or adverse effects). That is, while the medicine restores function to the area that has gone out of balance, it might also interrupt an area that has not.

Example 1: aspirin

When you take an aspirin, the desired effect might be to reduce your headache or fever. Aspirin will also reduce the ability of your blood to clot, which is the reason many older people take aspirin long term (in a low dose form) to reduce the risk of blood clots causing heart attack and stroke. However, regular aspirin use can upset your stomach - a side effect.

Example 2: iron supplements

Iron supplements can help rectify iron deficiency, but they may upset your stomach or cause constipation - the side effects.

How do I find out about the side effects of my medicines?

When you are talking to your doctor or pharmacist, it is useful to ask about any unwanted side effects of treatments. Then you know what to expect; and if you experience anything other than what has been described, or the side effect is causing you too much trouble, you should go back to your doctor or pharmacist to discuss the problem.

Questions to ask your doctor when starting a new medication

• What side effects might I experience?
• How likely am I to experience the side effects?
• If I experience side effects should I continue or stop the medication?
• If I continue with it, what can I do to ease the side effects?
• When should I call the doctor or visit the pharmacist about the side effects?

Doctors are able to assess the chances of you running into problems with particular treatments, as the known side effects are carefully detailed when a drug is registered for use in New Zealand. A very rare treatment side effect might occur in less than 1 in 10,000 users. A rare treatment side effect might occur in between 1 in 1000 and 1 in 10,000 users. An uncommon treatment side effect might occur in between 1 in 100 and 1 in 1000 users. A common treatment side effect might occur in between 1 in 10 and 1 in 100 users. A very common treatment side effect might occur in more than 1 in 10 users. No medical drug or procedure is 100% free of unwanted side effects. Treatments are prescribed by your doctor when the benefits for you outweigh the (usually very small) risk of side effects.

Getting to grips with risks Is the risk important? It may be that your doctor has recommended using a medication, in the hope it will relieve a medical problem. You read somewhere this treatment increases the risk of having a heart attack by 50%. This may seem worrying - however, a closer look at the risks may help put it into context. It may be that for someone of your age and in your state of health you already have an estimated 2% (2 in 100) risk of heart attack in the next five years. So, in effect, by taking the medication, your risk of heart attack would move up from 2% (2 in 100, or 1 in 50) to 3% (3 in 100, or about 1 in 33). Looking at the actual numbers can help you get the information you need to make a decision and decide whether a risk is relevant in the context of both your existing overall risk and the likely benefits of a new treatment.

How to minimise side effects

Most prescription medicine side effects are well known and are generally mild or temporary, such as upset stomach, nausea or a rash. Many side effects can be avoided if you tell your doctor or pharmacist about them - they may switch you to a similar medication or alter the dose or timing of use of the original one to stop the side effects. Most side effects start soon after beginning a new medication, but they can occur later on.

Some medications should be taken with food to help protect the stomach lining or to make sure they are absorbed properly. Others should be taken on an empty stomach. (Also see our topic Pharmacy labels - what do they mean?)

With all medications, it is a case of "Do the benefits outweigh the possible side effects of the treatment"? A doctor weighs up these pros and cons before deciding on a particular treatment for a particular patient. Many factors can influence this decision, such as:

• your age and general health
• pregnancy or breastfeeding
• other medications being used (including prescription and over-the-counter medicines, alternative medicines and supplements)
• other medical conditions
• and other considerations.

Important side effects, including allergic reactions with swelling of the lips or tongue, wheezing or difficulty breathing, require immediate medical attention. Call 111 if necessary.

For a pdf version of this health topic click here.

Original material provided by everybody and reviewed in March 2006.