Deciding whether to take or continue taking a particular prescription medicine involves weighing up the anticipated benefits and potential side effects, in consultation with your doctor and pharmacist.

Your decision will be influenced by many factors, including your beliefs about health and medicines in general, the nature and severity of your condition, your feelings about the benefits or anticipated benefits of the medicine, the likelihood of experiencing side effects, and your tolerance of the side effects.

For example, someone taking a medicine for a life-limiting condition may be more likely to tolerate severe side effects than someone taking a medicine for a minor condition. Because of the seriousness of their condition, they are more likely to feel that the potential benefits of the medicine outweigh the impact of the side effects.

Ask your doctor

Start the process of weighing up the benefits and side effects of a medicine when your doctor first suggests a new medicine.

No doctor can tell you with certainty what side effects you will or will not suffer, because everyone reacts differently to medicines. However, they can give you some guidance about your likelihood of having side effects based on their experience of treating other people with the medicine, and statistics about the medicine’s side effects.

With new medicines, the statistics are derived from clinical trials conducted on relatively small numbers of people, so usually only the more common side effects will have been seen. Rarer side effects that affect, say, less than 1 in 10,000 people may not have been seen.

In contrast, more statistics will have been collected for medicines that have been used by thousands of people over many years. As a result, more will be known about the side effects, and the rarer side effects are likely to have been seen.

Similarly, no doctor can tell you about all the potential side effects of a medicine. However, they should tell you about the ‘very common’ and ‘common’ side effects (see box below) and about any side effects that may be particularly relevant to you.

If you are unsure whether to start a medicine, ask your doctor to go through the pros and cons of the medicine and any alternatives until you have the information you need to make a decision.

If you are considering stopping a medicine because of the side effects, tell your doctor. They may be able to prescribe another medicine instead, or adjust the dose of your existing medicine so the side effects disappear or become more tolerable.

Ask your pharmacist

Don’t forget that pharmacists know a lot about medicines. They can usually answer any questions you may have, and give you further information about the medicine and its side effects.

If you are unsure whether a new symptom could be a side effect, consider talking to your pharmacist in the first instance. They will be able to tell you whether it could be a side effect and whether you should do something about it, such as going back to your doctor.

Read the CMI

Consumer Medicine Information (CMI) leaflets are specially prepared leaflets that give you comprehensive information about medicines: how they work, their side effects, how and when to take them, and so on. A CMI leaflet has been written for every prescription medicine.

Doctors have the CMI leaflets for most prescription medicines on their computers. When your doctor suggests a new medicine, ask them to print off the CMI leaflet. Both of you can then refer to it when discussing the potential benefits and side effects of the medicine. You can also highlight any important details on the leaflet, so you don’t forget them when you get home.

Your pharmacist should give you a CMI leaflet when you have a prescription for a new medicine filled for the first time, and on request thereafter.

Many CMI leaflets are also available on the internet at the National Prescribing Service website.

At first glance, the list of possible side effects in a CMI leaflet may be quite daunting. However, if you understand what the terms ‘very common’, ‘common’, ‘uncommon’, ‘rare’ and ‘very rare’ mean (see box above), you can put the likelihood of side effects into perspective.

Ring Medicines Line

You can ring Medicines Line, Australia’s national medicines information service for information and advice. The pharmacist on duty will answer your questions about medicines and their side effects. They can also post you the CMI leaflet for your medicine. Ring the service on 1300 888 763 Mondays to Fridays 9 am – 6 pm EST.