One of the most fearsome skin creams is called 5-fluorouracil, a powerful chemotherapy applied to precancerous and cancerous skin lesions. When improperly taken by mouth, this medication distributes itself throughout the entire body and exterminates select cell populations, beginning with the gut lining and the immune system. Smaller, repeated ingestions may bring about a different clinical syndrome, but both are devastating. A sizeable intake will cause seizures and death within a half a day or less.
Check your cabinets for calcipotriene cream, which is used to treat psoriasis and a few other skin conditions. It’s made from vitamin D, which is the only nutritional supplement that moonlights as rat bait. Licking this compound from human skin, or out of the package, causes calcium levels in the pet’s body to skyrocket, which is precisely how it ends the lives of rodents. This mineral imbalance is very difficult to correct and, in many cases, is deadly.
A third deadly drug is minoxidil, used to increase hair growth on balding scalps. It was originally developed as a blood pressure reducer, and that is how it behaves in small animals when they lick this off of bedding or off the surface of their favorite human being. Minoxidil is not supplied as a tidy cream, but instead in various forms that are easily spilled and splattered. It throws blood pressure way out of balance and can thus cause heart failure.
The final medicine poses a different sort of challenge for veterinarians: it’s a multi-drug cocktail for joint pain whipped up at the compounding pharmacy. Various different recipes exist, but they typically include muscle relaxers like baclofen or cyclobenzaprine mixed with high potency anti-inflammatories such as diclofenac, flurbiprofen, or naproxen (all of which are extremely poisonous to dogs and cats). These creams contain massive quantities of drug because only a small percentage of that is able to enter intact skin. Small daily exposures caused by licking the treatment site can cause just as much damage as puncturing and licking the tube. These prescription pain cocktails must be treated with great caution. Even over-the-counter joint creams such as HEET, Ben Gay, and Aspercreme are poisonous to dogs and cats. Note that natural wintergreen oil, used for the same purpose, is also toxic for pets.
Just one more installment is left: how to react when your physician writes you a prescription for one of these terrible topical toxins. Don’t panic—you don’t have to arm wrestle your doctor or sacrifice your own health to keep the family pet safe.
Dr. M.S. Regan