Using human medicines in pets
Paracetamol (acetaminophen) is one of the most commonly used over-the-counter medicines in humans because of its analgesic and antipyretic effects. Its widespread availability and perceived safety in people often lead to the mistaken belief that it can also be used safely in animals. This misconception is especially dangerous in cats, and it has become more relevant in recent times as cat numbers have apparently increased in Kashmir, with more cats living in close proximity to humans. Some pet owners administer human medicines such as paracetamol to cats, unaware that this practice can be fatal.
Cats are the species most severely affected by paracetamol toxicity and should never be given this drug under any circumstances. The feline liver lacks key enzymes, particularly those involved in glucuronidation, which are required for safe paracetamol metabolism. As a result, toxic metabolites accumulate rapidly in the body. Even a single human tablet can cause severe poisoning, leading to methemoglobinemia, in which hemoglobin loses its ability to carry oxygen, along with oxidative damage to red blood cells and acute liver failure. Clinical signs such as swelling of the face and paws, respiratory distress, cyanosis, and rapid deterioration are commonly observed, and death may occur quickly, often despite treatment.
Dogs are less sensitive to paracetamol than cats, but they still have a relatively narrow margin of safety. While dogs possess better metabolic capacity, overdose or repeated administration can result in liver damage, gastrointestinal ulceration, and, at higher doses, methemoglobinemia. For this reason, paracetamol should only be used in dogs under veterinary supervision, with careful attention to dose and duration.
Cats are highly sensitive to aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) because they metabolize these drugs very slowly, resulting in prolonged drug action and a high risk of toxicity even at low doses. Dogs generally tolerate NSAIDs better than cats; however, certain NSAIDs, particularly ibuprofen and diclofenac, can cause severe adverse effects in dogs, including gastric ulceration, renal injury, and neurological signs. COX-2 selective NSAIDs such as meloxicam and coxibs (e.g., robenacoxib) are comparatively safer in dogs and are among the few NSAIDs that can be used in cats.
Human topical preparations and cold–cough medicines are also sometimes used in pets. Analgesic gels, ointments, and sprays containing ingredients such as diclofenac, salicylates, menthol, camphor, lidocaine, or capsaicin are sometimes applied to dogs or cats for pain or swelling, or pets may lick treated human skin, with the belief that only very small amounts are absorbed. However, these products are often highly concentrated, and inappropriate use or repeated exposure—particularly in cats, which have limited drug-metabolizing capacity—can increase the risk of adverse effects.
In a similar way, human cold and cough preparations may be given to pets for signs like sneezing or coughing, without recognition that they frequently contain multiple active ingredients such as paracetamol, decongestants, caffeine, and cough suppressants, some of which can be harmful to animals when used incorrectly. The resulting effects may include gastrointestinal, neurological, cardiovascular, or hepatic disturbances, depending on the drug, dose, and species.
Dogs are also particularly sensitive to several everyday human substances. Theobromine present in chocolate and caffeine found in tea or coffee are poorly metabolized in dogs and can cause central nervous system stimulation, cardiac arrhythmias, tremors, seizures, and death. Xylitol, a sweetener and excipient commonly used in human medicines and sugar-free products, is highly toxic to dogs and can induce rapid insulin release, leading to severe hypoglycemia and acute liver failure.
These examples highlight a fundamental principle of pharmacology: drug safety is not determined by body size alone but by species-specific physiology, metabolic pathways, and enzyme systems. Human medicines should never be used in animals without veterinary advice, and safe storage of medicines is essential to prevent both intentional misuse and accidental poisoning.
