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by Beau Harger, PharmD, PCCA Clinical Compounding Pharmacist/Training Instructor
Popular compounds such as transdermal methimazole for hyperthyroidism and transdermal buprenorphine for pain in felines are common in the veterinary world. Not only has this delivery been a staple for pets like cats and dogs, in some instances, this method may be used for some exotic species as well. For example, delivery through the skin has been used under the wing in birds.
PCCA introduced PermE8® Anhydrous Gel, an anhydrous, permeation-enhancing base, in 2018. PermE8 is classified as an anhydrous base due to water activity below 0.6 (Aw < 0.6).2 Comparison testing between Lipoderm and PermE8 Anhydrous Gel was conducted in vitro using a human skin model that measured the skin percutaneous absorption of ketoprofen. Test results indicated that PermE8 performed comparably to Lipoderm and significantly outperformed Anhydrous Lipoderm®.2,3 Traditionally, anhydrous bases didn’t have a smooth feel; however, PermE8 offers a soothing, silky texture that makes application more enjoyable for patients. It was also formulated without preservatives and may be an option for those pets with sensitive skin.
It’s important for pharmacists and veterinarians alike to understand that not all drugs are good candidates for transdermal delivery.
Important considerations include:
Drugs with large molecular weights may not pass through the skin and antibiotics could produce low serum levels, resulting in antibiotic resistance. If the veterinarian recommends proceeding with transdermal administration, it is important that monitoring parameters are established to assess the effectiveness of the preparation.
When compounding with PermE8, we recommend not exceeding a 20% powder load. This could include the pure API alone or with commercially available drug tablets or capsules containing excipients. Appropriate wetting agents are propylene glycol, diethylene glycol monoethyl ether or ethyl alcohol at a 5-10% concentration. We also recommend using an electronic mortar and pestle (EMP) on a high setting before and after milling to ensure full incorporation of wetting agent and API.
Permeation-enhancing formulations offer options for veterinary patients who otherwise may not receive treatment. Compounding pharmacies that provide these therapies should consider and have access to the newest technology — for people as well as pets — to optimize their influence in their community and in the compounding industry.
PCCA members with clinical services access may contact our Clinical Services team for answers to questions about permeation-enhancing topical preparations, as well as other compounding concerns.
References
These statements are provided for educational purposes only. They have not been evaluated by the Food and Drug Administration, and are not to be interpreted as a promise, guarantee or claim of therapeutic efficacy or safety. The information contained herein is not intended to replace or substitute for conventional medical care or encourage its abandonment.