Medication Effects Magnified in Cats
One difference is the small size and weights of cats-with average healthy weights ranging from 8 to 15 pounds. Cat medicine is formulated with these weights in mind. Dosages of human medicines, meanwhile, are generally intended for bodies with weights of 90 pounds and up. Like human infants, because of their body weight cats are thus extremely sensitive to the effects of the average pill and capsule dosages of human medications. For example, even the tiniest dose of a common non-steroidal anti-inflammatory (NSAID) such as ibuprofen can cause stomach and intestinal ulcers.
Cats also metabolize things they have ingested differently than people would. In particular, their livers cannot handle human medicines but react to them as toxic cat poison. Thus, NSAIDs and acetaminophen products can cause liver damage within a few days or even lead to immediate death. Even formulas with aspirin derivatives-such as Kaopectate, which contains bismuth subsalicylate-can be toxic.
Psychotropic Medications also Dangerous
Also because of their size and different rates of metabolism, cats also react much more strongly to human psychotropic drugs. The effects of antidepressants and methylphenidate (stimulants for attention deficit disorder) are greatly magnified in cats to a degree that can be harmful, even fatal. Stimulants will cause dangerous rises in heart rate, blood pressure, and temperature, and seizures may also result. Even the low-grade stimulant pseuodephedrine, present in colds medications, can produce similar results.
Antidepressants may cause vomiting and lethargy, or serotonin syndrome may result-where the antidepressant causes the same symptoms as a stimulant, along with agitation, disorientation, and vocalization. Tricyclic antidepressants, meanwhile, can lead to harmful cardiac arrhythmias. The intended effects of the psychotropic drugs overwhelm the cat's much smaller brain and neural pathways, leading to these unintended results.
Other common medications similarly cause potentially harmful reactions in a cat's body because of size and metabolism differences between cats and humans. Drugs for human diabetes such as glipizide and glyburide can cause blood sugar drops leading to disorientation and seizures. Minoxidil (Rogaine) for hair loss can be fatal to cats. The muscle relaxant Baclofen can impair the central nervous system, causing anything from depression and disorientation to a coma and death. Even vitamin D can spike feline blood calcium to levels leading to kidney failure.
Seek Vet Approval or Help
In general, cats should be treated strictly with cat medicine. Use of human medicine for cats should be done only through a veterinarian. Veterinarians may make use of human sedatives during cat surgery, for example, but the vet understands the correct formula and dosage to give. If a cat has ingested any amount of a human medication, the caretaker should immediately call their vet or the ASPCA's 24-hour Poison Control Center hotline at (888) 426-4435.