Variable accuracy, precision, and consistency of compounded famciclovir formulated for management of feline herpesvirus-1 in cats
Objective: To evaluate compounded famciclovir suspensions for accuracy, precision, and consistency in drug content.
Procedures: Two compounded famciclovir concentrations were evaluated (250 and 400 mg/mL, 30 preparations total from nine 503A compounding pharmacies) with U.S. Food and Drug Administration (FDA)-approved famciclovir tablets as control. Drug quantification via high-performance liquid chromatography (with famciclovir reference standard and pramipexole internal standard) was performed at 0, 14, and 28 days with concentrations of 90%–110% of labeled dose considered acceptable (US Pharmacopoeia standards).
Results: FDA-approved tablets from three different manufacturers were found to be accurate and precise with acceptable drug content. A significantly greater mean deviation from labeled content was noted for 400 mg/mL suspensions (–52.9%) compared to 250 mg/mL suspensions (–18.0%). When assessing time points separately, 15/63 (24%) samples of 250 mg/mL and 0/27 (0%) samples of 400 mg/mL suspensions met the acceptance standards. Coefficients of variation (CV) in drug content among pharmacy batches ranged from 0.5% to 29%, with 5/10 formulations having significantly lower CV% compared to control (decreased precision). Similarly, drug content changed over time (0–28 days) in all compounded formulations, with both downward and upward trends observed (variable consistency).
Conclusions: Most compounded famciclovir formulations were inaccurate, imprecise, and inconsistent. FDA-approved famciclovir tablets may be preferred over compounded famciclovir formulations for the management of feline herpesvirus-1. If compounded famciclovir is used in practice, a concentration of 250 mg/mL is preferred over 400 mg/mL given the lower accuracy of the higher concentration.
This is the published version of the following article: O'Leary, Louise M., Rachel A. Allbaugh, Dwayne E. Schrunk, Thomas E. Olsen, and Lionel Sebbag. "Variable accuracy, precision, and consistency of compounded famciclovir formulated for management of feline herpesvirus‐1 in cats." Veterinary Ophthalmology (2021). DOI: 10.1111/vop.12910. Posted with permission.