Parasite prevention medicines are more likely to be effective, and thereby protect the treated animal, when they are used according to appropriately prescribed re-treatment intervals. “Compliance” and “adherence” are commonly and interchangeably used to describe how well the actual use of a medication agrees with the prescription instructions. However, these are not identical terms. “Compliance” refers to how closely the patient follows the prescriber’s advice, and use of this term carries the negative idea that any failure in medication use is the patient’s fault. “Adherence” indicates that the patient is making an effort to maintain a prescribed regimen, and this more positive interpretation is increasingly used for reporting medication use patterns [1]. Full adherence to a prescribed regimen is achieved when the correct medication is administered at the correct dose, at the correct time, over the complete dosing interval. Non-adherence results in suboptimal pharmacotherapy, and is a potential contributor to negative outcomes like parasite resistance or disease progression, decreased treatment satisfaction, reduced patient quality of life, and increased treatment costs [2,3,4]. A meta-analysis of 569 studies reporting adherence to physician-prescribed medical treatment between 1948 and 1998 found that patient non-adherence ranged from 0 to 95% with an average non-adherence rate of 24.8% [5]. Adherence to a therapeutic regimen is multifaceted, with failure to adhere attributed to more than one factor [1, 6, 7]. A review of ectoparasite resistance to medications concluded that the most likely cause of suspected lack of insecticide/acaricide efficacy is treatment deficiency rather than resistance [8].
Techniques used to measure adherence to medication recommendations have included patient self-reported methods (verbal interviews, diary studies or questionnaires), indirect non-self-reported methods (administrative claims, electronic monitors, pill count or canister weight) or direct non-self-reported methods (plasma drug concentration, biological marker or directly observed therapy) [9, 10]. Patient surveys are an example of a self-reported adherence measure that has the advantage of obtaining information from the patient’s perspective, including non-adherence reasons. Patient surveys also carry the disadvantage of patient recall and bias. There is no gold standard for measuring medication adherence but patient surveys are commonly used [11].
Studies on human patient adherence to prescribed treatment regimens generally report an inverse relationship between medication adherence and dosing frequency, with significantly higher adherence rates reported for medications with a longer duration of action and therefore decreased dosing frequency [12,13,14,15]. This inverse link between adherence and dosing frequency has been demonstrated across a variety of drug classes [16, 17]. This relationship is partially responsible for the current trend toward longer-acting formulations in human medicine [18, 19]. There is evidence for a similar relationship between adherence and dosing frequency in veterinary medicine. Pet owners administering short-term antimicrobials to dogs were nine times more likely to be compliant with a once or twice a day dosing regimen compared to a three times daily dosing regimen [20]. Longer-acting veterinary formulations are also becoming more widely available including extended duration heartworm preventives and antimicrobials. Over the past 20 years, monthly (or 4 week) re-treatment has been the standard dosing interval for most flea and tick treatments for dogs. In 2014, a systemic treatment option was introduced that offered up to 12 weeks of flea and tick protection following administration of a single oral chewable dose of fluralaner (Bravecto®, Merck Animal Health, Madison, NJ USA). There are currently long acting flea/tick collars available for dogs in the United States, that have label indications for multi-month efficacy (flumethrin and imidicloprid, 8 months; deltamethrin 6 months). This study looks at adherence that is the result of a single pet owner decision regarding periodic product administration that cannot be undone by accidental factors (like the loss of a collar).
The optimal measure of adherence is to record the actual administration of a dose of the flea/tick medication to the dog; however, this degree of supervision was impractical. As a surrogate, this study surveyed owners currently treating their dogs with oral fluralaner, a prescription-only chew containing the long-acting systemic insecticide and acaricide, for flea and tick protection. This inclusion criterion was used to standardize owner responses to treatment and to reduce the potential that owners were purchasing over-the-counter (OTC) flea and tick treatments that could not be monitored. This approach allowed evaluation of sales recorded in the practice management database to provide a more accurate estimate of treatments purchased. Fluralaner purchases were used as a surrogate measure to estimate the number of doses administered to dogs in the practice.
In summary, the objectives of this study were to use survey techniques to: describe veterinary recommended flea and tick treatment protocols; assess owner recollection of veterinary recommendations for flea and tick prevention; and record owner opinions regarding the required period of protection. In addition, an estimate of actual owner adherence to administering flea and tick protection was assessed through a detailed review of flea and tick treatment purchases from selected veterinary hospital records.
