By Deborah Clark

Atopic dermatitis is the most common reason for dog and cat owners to visit their local veterinary clinic. It also affects other species, such as horses and ferrets. In many cases, pet owners will approach a compounding pharmacist first before going to see their local veterinarian. This is a great opportunity for the compounder to show their value to the pet owner as well as the veterinarian who cares for the animal.

What Is Atopic Dermatitis?
Atopic dermatitis is an inflammatory, pruritic, allergic skin disease characterized by a hypersensitivity reaction of the skin to causative agents found in the environment of the animal.¹ These “triggers,” or allergens, can be present in the air—in the case of dust and pollen—in food or in grooming products, similarly to the triggers that we find in human patients.

Usually, there is a genetic predisposition to atopic dermatitis, and in dogs, there are several breeds that are prone to this condition: Chinese Shar-Pei, Wirehaired Fox Terrier, Golden Retriever, Dalmatian, Boxer, Boston Terrier, Labrador Retriever, Lhasa Apso, Scottish Terrier, Shih Tzu and West Highland White Terrier. Compromise of the normal barrier function of the skin can also occur in many animals due to licking and biting of the affected areas. Immunologic abnormalities may also be present.

Clinical signs usually occur on a seasonal basis, but may become year-round over time. Pruritus, or itchiness, is the classic sign of atopic dermatitis. In canines and felines, the feet, face, ears, flexible surfaces of the front legs, axillae and abdomen are the most commonly affected areas.1 Lesions can range from red, inflamed, itchy patches to infected sores that may be crusted over or open. In many cases, alopecia occurs, as well as darkening of the affected skin areas. Most of the lesions are caused by the licking and biting that the animal does to alleviate the itching.

Common Treatment Options
The main goal of treatment is to alleviate pruritus in order to allow the skin to heal appropriately.  The first measure of treatment is to remove any allergens that may be the causative agents.  Removing certain things from the animal’s diet, such as grains, can many times help reverse the process. Environmental allergens, such as pollens, sometimes are not as easy to remove, and measures have to be taken to prevent reactions to them by the immune system.

Treatment can be initiated several different ways. In many cases, veterinarians will treat atopy with systemic medications, such as Apoquel® (oclacitinib), a Janus kinase inhibitor used in canines. Atopica® (cyclosporine, modified), a calcineurin inhibitor, is another agent used in canines and felines for treatment of atopy. These medications work well for many patients.

However, Apoquel has a history of being unavailable for periods of time, which is a frustration for veterinarians. Barriers to oral administration, such as biting, clawing, scratching or hiding, can also be issues for pet owners having to give these medications to their pets.

Compounding Ideas
The compounding pharmacist can be a huge aid to the owner and the veterinarian by offering different dosage forms, active pharmaceutical ingredients and bases that have advantages in these cases. Apoquel tablets can be compounded into a fixed oil suspension formula to aid in administration. PCCA Formula #9271 would be appropriate to use in this case, and PCCA members can access it here. When a more concentrated solution of cyclosporine is needed to aid administration, PCCA Formula #4815, an oral veterinary solution, is an option. PCCA members can access it here. As with any dosage-form changes, it would be important to monitor the patient in these situations because altering the dosage form may change the pharmacokinetics of the active ingredient.

Topical medications can be helpful for veterinary patients with atopic dermatitis either alone or in conjunction with the two previously mentioned drugs as well. Creams, gels, ointment and shampoos are the various dosage forms that can be compounded. However, one major issue with using creams, gels and ointments is they can mat the fur and make it greasy or sticky when applied. This is very undesirable for many owners, especially those with show animals where appearance is extremely important. The compounder can reformulate these products for the veterinarian using a base that soothes skin and does not mat the fur, such as PCCA’s ZoSil®.

ZoSil is a silicone hydrogel base designed specifically for animal skin. It’s rich in fatty acids, such as omega 3, omega 6 and conjugated linoleic acid. It also contains shea butter and hyaluronic acid. ZoSil uses Smart Diffusion Technology™ to release these ingredients, which are important in soothing and moisturizing, and help improve the appearance of red, flaky and irritated skin. The Smart Diffusion Technology works by encapsulating the previously mentioned ingredients in microscopic spheres that dissolve in the presence of lipases and phospholipidases normally released by the inflammatory response of the skin. However, this technology works in the absence of inflammation as well, as the spheres dissolve over time in the absence of the enzymes.

This combination of ingredients nourishes the skin and makes ZoSil a great choice in formulations for veterinary patients experiencing atopic dermatitis. Active pharmaceutical ingredients such as antibiotics, antifungals, anti-inflammatories, anesthetics, antiseptics and mast-cell stabilizers can be used in formulations with ZoSil.

Getting started in veterinary compounding? PCCA Clinical Compounding Pharmacist Mark Gonzalez has some advice.

Naltrexone is one active ingredient that may be helpful for patients experiencing atopic dermatitis. In a study published in the Journal of the American Veterinary Medical Association, canine patients were successfully treated with oral naltrexone for acral lick granulomas that were a result of atopy. The licking behavior may be reinforced by a decrease in pain perception due to the release of endogenous opioids. The theorized mechanism of action is that the naltrexone blocked the release of endogenous opioids, which increased the perception of pain and abated the licking behavior.² Naltrexone may be used topically in this same manner.

Tranilast,* a mast-cell stabilizer, is also a good option. It may be used orally or topically. In cases where the skin barrier has been compromised and infection has set in, antibiotics and antifungals may be used as well. Active pharmaceutical ingredients that address itching and inflammation may also be helpful.

Formulas to Consider
PCCA has a number of formulas that may be clinically relevant for veterinary patients with atopic dermatitis, including some that have been evaluated in our FormulaPlus™ program and have extended beyond-use dates backed by stability-indicating assays. PCCA members can access them here.

If PCCA members have any questions about ZoSil or compounding for veterinary atopic dermatitis, please call our Clinical Services department at 800.331.2498.

Deborah Clark, BSPharm, RPh, is a Clinical Compounding Pharmacist at PCCA. She previously worked in two independent hybrid pharmacies in Charlotte, North Carolina, managing compounding operations. While there, she worked with a local veterinary specialty and emergency hospital providing compounded medications for challenging veterinary patients. She also worked with the Carolina Raptor Center and several smaller veterinary clinics in the Charlotte Metro area. Deborah’s compounding experience also includes hospice, hormone replacement therapy, pain management, wound care, sterile products and pediatrics. She is certified in medication therapy management, and she is an associate member of the Society of Veterinary Hospital Pharmacists.

A version of this article was originally published in the Apothagram, PCCA’s members-only magazine.

References
1.    Moriello, K. A. (n.d.). Overview of atopic dermatitis. Merck Veterinary Manual. Retrieved from http://www.merckvetmanual.com/integumentary-system/atopic-dermatitis/overview-of-atopic-dermatitis 
2.    White, S. D. (1990). Naltrexone for treatment of acral lick dermatitis in dogs. Journal of the American Veterinary Medical Association, 196(7), 1073-1138.

*In February 2019, the U.S. Food and Drug Administration announced that it would not add tranilast to its list of bulk drug substances that can be compounded in medications for human use. However, this ruling does not affect compounded medications for veterinary patients. Therefore, tranilast is still an option in veterinary compounding.

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 references cited did not necessarily evaluate PCCA products or formulas included in these statements. The information contained herein is not intended to replace or substitute for conventional medical care, or encourage its abandonment.