Multiple studies in cats have demonstrated that drugs delivered via topically applied pluronic lecithin (PLO) gels do not predictably reach the blood stream. Yet, PLO gels continue to be promoted and compounded by pharmacists and prescribed by practitioners. Further, practitioners anecdotally report clinical response with their use.
The discrepancy between experimental results and clinical use may reflect study duration, which generally has been a single dose. Multiple dosing may be necessary before drug penetration is effective and response can occur. This study proposes to document the presence of drugs administered as PLO gels in spontaneously ill cats. Three drugs will be studied: methimazole, metronidazole, and prednisolone/prednisone.
Accuracy of compounded products and stability (potency) throughout the dosing period will be determined for each drug administered to 25 cats as a PLO gel and 25 matching (control) cats receiving the drug orally. Blood levels (peak and trough) will be monitored on day two, and intermittently for a maximum of 4 times for up to 3 months. Evidence of clinical response will be based on client and veterinary assessment. Endpoints will be compared between oral and PLO routes. Endpoints will include, for each cat, the magnitude of plasma drug concentrations, time to peak concentration, time to therapeutic concentration, and therapeutic response (yes or no). For each product, percent accuracy of compounded product and duration of potency will be determined such that an expiration date can be offered.