Thankfully, harmful, unexpected side-effects to animal medicines are extremely uncommon. Before any animal medicine is allowed onto the UK market it has, by law, to satisfy very strict criteria on its quality, its effectiveness and its safety. However, once an animal medicine is in use, it is vital to know if any animals or people suffer unexpected problems following use or exposure to the product under field conditions.

Very occasionally animals may show some small mild reaction to a medicine - just as humans may feel drowsy after certain common medications. If you are an animal owner and your animal is unwell after treatment with an animal medicine or if you are at all worried, contact your vet. This is just common-sense, whether or not your animal has received medication, and it is more than likely that the illness is totally unrelated to the medicine.

The Veterinary Medicines Directorate (VMD), which administers the licensing system, runs a scheme to monitor reports of any reactions in animals and people following the use of animal medicines, called the Suspected Adverse Reaction Surveillance Scheme.

The purpose of the scheme is to monitor trends in reported suspected reactions. Reports received by the VMD are prioritised in terms of severity and likely causality (i.e. to see whether the problem is likely to be linked to the medicine). The scheme also analyses whether there have been any other reports about the same product or others like it, whether any further information is required and whether any follow-up is required.