Medicines

Any medicine (including vaccines and herbal/homeopathic medicines) can cause an unwanted side effect. These are commonly referred to as an adverse drug reaction (ADR) by healthcare professionals. Side effects can result from taking either prescription medicines or those purchased at a pharmacy or retail outlet (for example a supermarket).

What is a medicine?

A medicine helps to treat or prevent disease, and can be made up of synthetic (pharmaceutically prepared), herbal or homeopathic active ingredients.

Most medicines come in a variety of types or formats, some are only available on prescription from your GP or other healthcare professional (such as a hospital doctor) some are available from a pharmacy where a pharmacist is present (such as a mild-steroid cream) and others can be purchased from supermarkets or other retail premises (such as some aspirin etc).

Medicines come in different forms, including:

tablets and powders
cough syrups
drops for the eyes or ears
asthma inhaler holding medication
hay fever and allergy tablets
skin creams or gels

In the UK, unless all the information relating to the medicine is on the packaging, a patient information leaflet (PIL) will be included inside the pack. This lists important information including common side effects that can occur when taking the medicine. However, everyone is different and our bodies may have different experiences with different medications.

Side effects and adverse reactions to medicines

A side effect is an unexpected effect that happens in addition to the main intended effect (of the medicine). An adverse reaction is when the resulting effect causes harm (this can be both physical and mental).

Side effects can happen at any time, but particularly when you:

take or use a medicine for the first time
stop taking a product after long-term usage
change a dosage of a product you already take
take a product that interacts with another medicine or device.

A medicine interaction happens when another substance affects the way a medicine works. For example, this could be another medicine, food, drink or herbal supplement.

Types of interaction include:

drug–drug interactions, when two or more healthcare products interact
drug–food interactions, when a certain food changes the action of a medicine.

Side effects could also be the result of defective, fake/unauthorised medicines (one that is not authentic).

Defective medicines

A defective medicine is a product that is not working properly or not to the manufacturer’s specifications.

If you do not think your medicine is good enough to take or use, report this to the MHRA’s Yellow Card scheme. You can also consult your doctor or pharmacist who can provide advice and report to us.

Defects in medicines can occur due to:

Quality issues with the product itself
Quality issues with the packaging (carton, blister pack)
Problems with other packaging components, such as the patient information leaflet (PIL)
Lack of efficacy which can be decided by speaking to a pharmacist or healthcare professional.

Fake/unauthorised medicines

A fake medicine is a product that tries to pass off as a genuine authorised medicine. An unauthorised medicine does not hold the relevant authorisations for sale and supply to patients in the UK and the MHRA has no evidence of its safety, quality or effectiveness.

Look out for signs such as:

being different to how it is described and how it looks
any misrepresentation concerning what it is, where it has come from or details provided on the packaging (e.g. expiry date).

You can find tips on how to safely obtain medicines online through our #FakeMeds campaign.

Why report side effects to the Yellow Card scheme?

Everyone has a different genetic makeup and therefore it is very difficult to predict whether an individual will experience a side effect. Whether you are a healthcare professional or a member of the public, you can help others by reporting side effects which you or your patients experience to the MHRA Yellow Card scheme. Reports help us gain a better understanding of medicine interactions and safeguard patients through vigilant monitoring.