What are side effects?

Side effects, otherwise known as adverse effects, describe the unwanted effects of medicines.

All medicines may cause a number of side effects, especially if they are not used as prescribed. The severity of side effects varies from mild drowsiness or nausea to life-threatening conditions.

Side effects may be predictable (expected) and are an extension of the way the medicines work, for example, anticholinergic medicines. These medicines are intended to decrease spasms of the gastrointestinal tract but can also cause blurred vision, retention of urine and dry mouth, which are also anticholinergic effects.

Sometimes side effects are unpredictable (not expected) and are not related to the way the medicines work. These can include allergies, and a large range of other effects on various body organs, such as your heart.

The side effects of medicines are listed in the patient information leaflet (PIL) that is included with the medicine. This will tell you which side effects are common and which side effects are rare.

Will I get side effects?

The risk of experiencing side effects varies.

Most people experience some side effects, and these are generally the less severe side effects such as mild drowsiness or mild nausea.

Classifying side effects

These real life examples from Bandolier may help us understand the risk of getting side effects from medicines:

• Common - between 1 in 100 and 1 in 10 is similar to the risk of dying from cancer after smoking 20 cigarettes a day for 30 years.
• Uncommon - between 1 in 1,000 and 1 in 100 is similar to being injured on stairs in the next 12 months.
• Rare - between 1 in 10,000 and 1 in 1,000 is similar to dying at home in an accident in the next 12 months.
• Very rare - between 1 in 100,000 and 1 in 10,000 is similar to being killed by lightning.

What to do if you experience side effects

If you experience a mild side effect, which you feel you can manage on your own, there is no need to see a doctor. However if you think you have a side effect which is listed as serious in the PIL, or which you think is serious, contact your doctor or pharmacist immediately.

Also, if you think you may be having a serious allergic reaction, contact your doctor or call 911 immediately.