The Transdermal Trend

an Easier Way to Medicate Cats

Lucy Drury

At some point in time, nearly every cat owner, whether they have one or twenty furry family members, will hear those dreaded words from their vet: “Would you like this medication in tablet form or liquid?” Even the most experienced of breeders will likely have memories of pink spots on white shirts as they were trying to get to work that morning after medicating Fluffys—or recall the carefully extracted pill found on the floor after being certain that it had been successfully inserted down her throat.

Even if your cat is relatively easy to “pill”, some medications present a threat to the esophagus if they are not given with food and/or flushed down with water, such as doxycycline and clindamycin.2

In many cases, there is an alternative to these struggles—transdermal medications. These medications are applied directly to the skin. In a cat, the typical application site is inside the ear, where there is little to no hair. They are compounded for this purpose by veterinary pharmacies. The medication is measured out in a syringe, and then applied to the inside of the ear with gloved fingers, so that the medication is not inadvertently transferred to the human.4 Most cats tolerate the application well, particularly if treats are given afterwards. In a few cases, the cat may be sensitive to the gel but the irritation usually resolves after the treatment is complete. Some medications, such as the commonly prescribed analgesic fentanyl, can be delivered via a transdermal patch.3

 

Though transdermal delivery of some commonly prescribed medication for cats has been available for over a decade, many cat owners do not know this is an option. Not every medication is suitable for delivery through the skin, particularly those given for gastro- intestinal issues.6 A few of the more commonly used drugs in transdermal form are: methimazole (hyperthyroidism), amitriptyline (behavioral issues and pain relief), prednisolone (corticosteroid anti-inflammatory), Prozac (behavioral), diphenhydramine (anti- histamine), enrofloxacin (antibiotic), amlodipine and benazepril (hypertension), and mirtazapine (appetite stimulation).1,2,4,6

Some of the drugs available in a transdermal form include: (2,4,5)

  • amikacin
  • amitriptyline
  • amlodipine
  • benazepril
  • chlorpheniramine
  • cisapride
  • comipramine
  • diltiazem
  • diphenhydramine
  • enrofloxacin
  • famotidine
  • fentanyl
  • fluoxetine
  • ketoconazole
  • mirtazapine
  • methimazole
  • metronidazole
  • nitroglycerin
  • phenylpropanolamine
  • prednisolone
  • prednisone

Before you go rushing out to ask your veterinarian for all your medications in transdermal form, there are a few important factors you need to keep in mind. In particular, you should be aware that the safety and efficacy of drugs delivered via the transdermal route, has not been well studied for every candidate drug. There are some medications that have been extensively studied, such as methimazole for hyperthyroidism, and their safety and efficacy has been well established.1 However, Dr. Susan Little recommends that in the absence of data regarding effective transdermal delivery for a medication, the transdermal route not be used if a condition is serious and an immediate outcome is desired (e.g. seizures, hypertension). She also recommends that if there is not a lot of data for a particular pharmaceutical, but the condition is not serious, it should be used for conditions where the outcome is measurable (heart rate, blood glucose). She also cautions against using antibiotics in a transdermal form, as therapeutic levels may not be reached and the pathogen could develop a resistance to the antibiotic.2

Another drawback to the transdermal route is cost. Pharmacies usually will need to compound the prescription by hand with the gel and prepare the syringes for the patient, as the dose is usually body weight dependent.4,5 This is a labor-intensive process which adds significantly to the cost. Owners should never try to create their own transdermal medication unless they are licensed pharmacists or veterinarians. Absorption rates vary, and simply taking an oral medication and mixing it with the delivery gel can result in levels that are toxic or sub-therapeutic.

Nevertheless, if your cat is one of those that is impossible to “pill,” it does no harm to ask your vet if a prescribed medication is available in a transdermal form. If the answer is “yes,” be sure to investigate the pros and cons of transdermal delivery for that medication. It may be possible for you to avoid those early-morning battles and/or “rediscovered’ pills. And if so, your cat should be grateful!

References

1. Lécuyer, M., Prini, S., Dunn, M. E., & Doucet, M. Y. (2006). Clinical efficacy and safety of transdermal methimazole in the treatment of feline hyperthyroidism. The Canadian veterinary journal = La revue veterinaire canadienne, 47(2), 131–135.
2. Little, Susan (2008). Transdermal Medications and More (CVC in Kansas City Proceedings). DVM 360.

3. M Scherk-Nixon (1996) A study of the use of a transdermal fentanyl patch in cats. Journal of the American Animal Hospital Association: January 1996, Vol. 32, No. 1, pp. 19-24.
4. Transdermal Medications – Great Option and Available if your Cat needs them! Belle Mead Animal Hospital. (2014 June 16). Retrieved from: https://www.bellemead- animalhospital.com/blog/transdermal-medications-great-option-and-available-if-your- cat-needs-them/.

5. Transdermals. BCP Veterinary Pharmacy (2019, June 20) Retrieved from: https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/ transdermal
6. Trepanier, Lauren A. Guidelines and Precautions for Drug Therapy in Cats. The Cat. (2012). Retrieved from: https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/transdermal

Originally published in Cat Talk Magazine