This is a question that seems to be popping up an awful lot on the internet at the moment… People wondering if they can use paracetamol, or ibuprofen or aspirin as painkillers for their dogs, or giving any kind of painkiller to their cat. At the moment, of course, this is a really big deal – with so many vets on “emergencies only”, it can be very tempting to try to medicate your pet at home. The short advice, though, is don’t try this at home. While there are some human painkilling drugs that can be used in dogs and cats, they all have potentially serious and even life-threatening side effects, and poisoning is sadly really common.

How would I know if my pet was in pain?

Different animals show pain in different ways. Although it does vary a lot between individuals, we can say that common signs include:


  • Altered behaviour (e.g. growling, whining, or withdrawing)
  • Being more “clingy”
  • Limping, or guarding the injured body part
  • Crying out (although this is less common than most people think!)
  • Reluctance to move
  • Increased breathing rate
  • Hunched posture
  • General depression and lethargy (especially in chronic or long-term pain)


  • Hiding away or withdrawal
  • Reduced appetite
  • Aggression or grumpiness
  • Increased breathing rate
  • Hunchedor rigid posture
  • Lameness or guarding is often only seen in the advanced stages

Rabbits and other small pets:

  • Withdrawal
  • Freezing
  • Increased breathing rate

Note that cats, rabbits and small pets are often very good at hiding their pain – whereas most dogs are much more open about it! There’s a good blog article about pain from my colleague Martin here.

What are painkillers?

“Painkillers”, or analgesics, are a very large group of drugs, containing many different families. They include the non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, aspirin, meloxicam and carprofen; as well as the more distantly related paracetamol (acetaminofen if you’re in the States). These are the most common class and most widely used; however, opioids (derived from morphine, and including codeine, fentanyl, and buprenorphine) are also quite commonly used in UK vet practices, as are tramadol (acts as an opioid in humans and cats, but more like an antidepressant in dogs) and gabapentin (which is really good for nerve pain). There are others too (e.g. ketamine or amantadine), but they’re much more rarely used as painkillers in general practice.

All of these medications have different uses and possible side effects, so it’s very difficult to group them all together! You can read more detail about the different classes here.

What are the side effects?

It depends on the class, but common effects include…

  • NSAIDs – vomiting, diarrhoea, stomach ulcers, even kidney failure in some cases. Ibuprofen and naproxen are very dangerous to dogs as they do not tolerate the side effects as well as most humans do.
  • Paracetamol – damage to the blood (methaemoglobinaemia), swelling of face and paws, liver failure. Frequently fatal in cats, and sometimes in dogs.
  • Opioids – abnormal behaviour, sedation, constipation, coma, difficulty breathing, even death from respiratory failure. The safe doses are much lower than for humans.
  • Tramadol and gabapentin – sedation and/or abnormal behaviour.

So why does my vet prescribe them if they’re so dangerous?

It is never acceptable to leave an animal in pain if there’s anything that we can reasonably do to control it. With the range of drugs available, there are very, very few conditions where we cannot safely control the pain. 

Why aren’t dog-safe versions available over the counter, like paracetamol for humans?

If paracetamol was a new drug, it’s very unlikely that it would get a license nowadays! However, there’s a bigger issue – dosage. While most adult humans are much the same size (perhaps 60-120kg), healthy adult weights for dogs vary from 1kg Chihuahuas to 100kh Newfoundlands. Given the risk of toxicity at overdose, the VMD hasn’t licensed any “over the counter” medications. To add to the complications, if your pet is in pain, you have a legal duty under the Animal Welfare Act 2006 to seek veterinary advice – so there’s very little scope to legally use over the counter painkillers anyway. 

Why is the dose different?

Clearly, a dose of painkiller for a 75kg human is likely to be a massive overdose for a 5kg cat, or even a 20kg dog. However, we also need to remember that dogs and cats are different species to us. They have different metabolic pathways to humans – humans can break down many drugs (including most painkillers) faster than our pets can, meaning that even the dose per kg bodyweight may be very different. For example, paracetamol is rapidly fatal to most cats, even in tiny amounts.

But what if I need urgent pain relief for my dog?

Do not give them anything from your bathroom cupboard without talking to your vet! Instead, call your vet – if it’s an emergency, they can give you instructions on what to use. This is because they know the safe doses, given your patient’s medical history. 

Remember, it is illegal in the UK and EU to make that decision yourself, though, or to buy human medication specifically for your pet without a veterinary prescription.

If your pet is in pain – contact your vet immediately for advice. Don’t try to manage without and leave them suffering! Even in lockdown, your vet will be able to advise you, and will see emergency cases.