Hillcrest Animal Hospital, Chorley

Can I use human medicines in my pets?

January 23, 2017

Simple answer - no. Although human medications are often cheaper than the veterinary equivalents, it’s often really unwise to use them - not only is it illegal, but it is also dangerous to your animals.

How can it be dangerous if it’s a proper medicine?

Just because it’s a proper medicine that’s safe for humans, doesn’t mean it’s safe for animals! There are two reasons for this:

  • Body size. The safe dose for any drug in any species (including humans) depends on how big the animal is. The larger they are, the higher a dose they will need, but also the more efficiently they'll break it down. Giving a small animal the same dose of a medication as a large one will result in overdose, which can be harmful, or even fatal. The average human weighs about 70kg; the average dog weighs about 25kg, while most cats come in at roughly 4kg. So, giving a dog or a cat a human-size dose is always going to be potentially dangerous!
  • Species differences. Different animals handle toxic substances (like most medications) differently. In general, humans break down toxic chemicals more effectively than any other mammal, which is why you can never assume that a human-safe drug is pet-safe! Typical examples are paracetamol (lethal to cats even in tiny doses, because their livers cannot convert it into harmlessness) and ibuprofen (really dangerous for dogs, who suffer from kidney toxicity and stomach ulcers even at low doses).

Surely it’s legal to do whatever I like with over the counter medicines?

The way that medicines are licensed, these drugs are only over the counter for human use. As soon as you intend to give them to an animal they become prescription-only, meaning that it is a criminal offence to give them to an animal without a prescription from your vet.

What about left-over veterinary medicines - surely I can save money by buying them from someone who hasn’t used up their prescription?

Definitely not! Reselling of prescription medicines is also illegal. Once dispensed, they cannot be resold, and must be either used by the animal for which they have been prescribed, or destroyed.

Why do vets always prescribe expensive veterinary medicines not the cheaper human form - after all, doctors prescribe the cheapest version, why can’t vets?

Unfortunately, in UK law it is a criminal offence for a vet to use or prescribe any medication other than one licensed for that species, for that disease or condition.

The only exceptions to this are if there is no suitable medication, or if the licensed medicines are unsafe or ineffective in that particular animal. In these situations, vets are obliged to use a system called the Prescribing Cascade, which describes which drugs can be used:

  1. A licensed drug for that condition in that species. If there isn’t a suitable or available drug, go to…
  2. A licensed veterinary drug for a different condition in that species, or…
  3. A licensed veterinary drug for that condition in a different species. Only if there is still nothing available can we prescribe:
  4. A human medication.

The law also specifically bans us from using the Cascade for reasons of cost as well. You can learn more about the Cascade here: https://www.gov.uk/guidance/the-cascade-prescribing-unauthorised-medicines

Vets who breach these rules may face criminal prosecution; even if this doesn’t occur, we are likely to be disciplined by the RCVS, which will usually result in us being banned from practicing. So, if we will only prescribe a veterinary medicine, there are good reasons!

If you have any queries about your pet’s medicines, please give us a call to talk to one of our vets!