An adverse drug reaction is a term used to describe when cats have an undesired response to a medicinal product. This includes anything from injections to topical medications, like creams or ear drops. There are many different types of adverse reactions. Adverse drug reactions can be challenging to diagnose, as the symptoms are often vague.
It’s important to understand that vets choose and administer medications with precision, based on extensive clinical studies and evidence to determine the appropriate dosage and treatment. Any cat can potentially develop a reaction to any drug. Adverse drug reactions can range from very mild to severe, including death. Severe reactions are rare and most drug reactions only result in mild signs.
What to do
What to do if your cat is showing signs of an adverse drug reaction
Contact a vet as soon as possible:
- Let the vet know of any symptoms your cat is showing
- Determine if your cat got a larger dose than recommended at home
- Stay calm and avoid seeking advice on internet forums; these can be full of misinformation.
Most adverse drug reactions are mild and can be monitored or treated at home. Our Joii vets are available 24 hours a day for advice. Call us now if you have any questions.
Causes
Most common causes of adverse drug reactions in cats
The most common reported reactions are those from:
- Vaccinations
- Antimicrobial medications, such as antibiotics
- Non steroidal anti-inflammatory medications (NSAIDs)
- Parasite preventatives
- Anaesthetic agents
These are the most commonly used medications in veterinary medicine, so it’s likely that this is why we see more reactions reported, rather than these being more risky.
When to worry
When to worry about an adverse drug reaction in cats
An emergency exam will be needed if your cat:
- Has severe vomiting and diarrhoea
- Is showing any neurological signs, such as incoordination or seizures
- Has breathing problems
Call us and speak to one of our Joii vets if your cat:
- Has mild vomiting or diarrhoea
- Has itchy or red skin
Prevention
Tips on how to prevent adverse drug reactions in cats
- Always stick to the dose that your vet has prescribed. If the dosage is unclear, speak to your vet before giving it to your cat.
- If you miss a dose or overdose by accident, always check with your vet before giving any further medication.
- Never give your cat human medications, many of these are toxic to them.
- For cats on long-term medication, attend regular check-ups with your vet. Routine blood and urine tests are advised for monitoring certain medications.
Diagnosis
How to know if your cat is having an adverse drug reaction
Adverse drug reactions are difficult to diagnose, as the symptoms tend to be quite vague and can have many different causes. Symptoms, especially severe ones, usually develop within a few hours but can be up to 2-3 days later.
The most common symptoms of drug reactions include:
- Vomiting
- Diarrhoea
- Lethargy
- Reduced or increased appetite
- Increased thirst
- Skin reactions: itching, redness, hives and hair loss
- Drooling
- Sedation
Severe allergic reactions are rare but life-threatening. Symptoms include:
- Difficulty breathing
- Red or blue gums
- Seizures
- Collapse
Home treatment
How to help at home if your cat has an adverse drug reaction
Most cases of mild reactions can be treated at home:
- Feeding small meals of bland food can help cats with tummy upsets
- Heating the food slightly can help with palatability increasing appetite
- Allow your cat to rest and monitor for any new symptoms
- For itchy cats, using a buster collar can help reduce self-trauma
- If the reaction occurred after applying a product to the skin, wash the area thoroughly to remove the product as much as possible
Vet treatment
Treatment for adverse drug reactions in cats
Treatment depends on how severe the reaction is. It mostly involves removing any drug still present in the body and symptomatic treatment.
This may include:
- Emergency treatment for anaphylactic reactions: hospitalisation, fluids via a drip, and emergency medications
- Anti-seizure medication
- Antihistamines and/or corticosteroids
- Activated charcoal: to reduce further absorption of the drug
- Induced vomiting, if caught early and before any signs of reaction develop
- Antidotes: if available, though these are not common in vet medicine
Risk
Are some cats more at risk of adverse drug reactions?
- Age can have an effect on how the body processes certain medications. Both very young and elderly cats may be more likely to have reactions to medications.
- Cats with liver disease, because this is the organ where drugs and medications are processed.
- Cats with kidney disease because that’s where drugs are eliminated.
- Cats with heart disease may also have an increased risk.
- Cats with allergies (atopy).
- Cats with the MDR1 gene mutation have a higher risk of reactions to certain medications, such as Ivermectin. In dogs, this is usually breed-specific, but it can appear in any breed of cat.
- Cats that have had a previous reaction to a medication are more likely to have a repeat reaction to the same medication. These further reactions can be more severe.
Other less common risks
- Adverse drug reactions can lead to transient problems in the liver and kidneys. These often improve once the medication is stopped.
- Another less common side effect is auto-immune disease, such as immune-mediated haemolytic anaemia.
- Stomach ulcers caused by NSAIDs and steroids.
- Lumps caused by injection reactions.
- Neurological signs, such as incoordination and seizures due to flea or tick preventatives.
