Medication side effects - protecting yourself and others

How do you know the medicine you're taking is safe? Well, you can trust your doctor (I would say that, wouldn't I!) to use all the information they have to weigh up the risks and benefits for you. But what if your doctor doesn't know either?

For a medicine to be licensed (approved for prescribing by doctors) in the UK, it has to jump through hundreds of hoops. In the UK, the Medicines and Healthcare Products Regulatory Agency (MHRA) is responsible for weighing up all the evidence for all medicines and medical devices in the UK and deciding whether they work and are acceptably safe. Before the MHRA licenses a medicine, it looks at all the scientific studies a new medicine has been put through, the dose which offers the best ratio of effectiveness and safety, the condition it's trying to treat, the length of treatment and a host of other factors.

High-quality scientific trials compare the medicine being studied either with another medicine which is already licensed or with a placebo. A placebo is a 'pretend' medicine with no active ingredient. But importantly in placebo-controlled trials, neither the doctor nor the patient knows if they're taking 'the real thing'. If one in three patients gets a nasty rash or chest pain while taking the medicine being studied, it would probably never get licensed - unless exactly the same proportion of patients gets the same symptoms when they're taking the placebo but don't know which of the two they've been given.

This system is good, but it isn't totally foolproof. Some side effects are rare, and may not be picked up by trials even on thousands of people. Others are really common, but happen often in people who aren't on the medicine either. For instance, just in the last few weeks a major review has linked high doses of the common anti-inflammatory tablets ibuprofen and diclofenac with an increased risk of heart disease. They've both been around for years, but it's only when many millions of doses of some medicines have been given that the true size of the problem comes to light.

That's where the MHRA's Yellow Card system comes in. While pharmaceutical companies are obliged to inform the MHRA about potential side effects as soon as it becomes aware of them, it's voluntary for doctors and patients. If you get a side effect from a medicine, you can check in the medicines section of, or with your pharmacist or GP, about whether it's recognised and considered potentially serious. You can then decide yourself whether to report the side effect simply by visiting

Some side effects are well known - for instance, the blood pressure lowering medicine amlodipine commonly causes ankle swelling. This side effect doesn't seem to be linked to any more serious problems, and reporting it to the MHRA might not change the view of the benefit-risk profile. But even if side effects are known about, a rise in the number of people reporting them could change the warnings on the labels or even cause the MHRA to restrict its use or change the dose. Perhaps even more important is getting a side effect that could be serious, but isn't widely known. Patient reports have been proven to provide different information to those from their doctors or pharmacists, including the impact of side effects on patients' lives.

The more patients who report these side effects through the Yellow Card scheme, the easier it is for the MHRA to build up a picture of possible problems - and to protect us, as patients, from them.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.