Dried blood spot analysis of donepezil in support of a GLP 3-month dose-range finding study in rats.

Donepezil hydrochloride is a reversible acetyl cholinesterase inhibitor approved for Alzheimer disease treatment. As an alternate therapy, a donepezil hydrochloride transdermal patch is in development. Recommended nonclinical safety studies include a 3-month Good Laboratory Practice (GLP) dose-range finding (DRF) study prior to conducting the 2-year dermal carcinogenicity study in rats. Demonstration of systemic exposure is necessary to interpret the in vivo data. Previous nonclinical reports supporting oral dosing have utilized liquid chromatography tandem mass spectrometry (LC/MS/MS) to quantify donepezil concentrations in plasma. Smaller species with limited blood volumes do not allow serial sampling to derive the full pharmacokinetic profile from a single animal. Therefore, the option of another analytical method requiring decreased sample volumes is desirable as it would decrease the required number of animals while obtaining the complete profile. The dried blood spot (DBS) technique allows drug level measurement from a few microliters; however, the method is still not widely utilized in GLP studies. Because donepezil plasma levels are known by the oral route, DBS was used to bridge the previous oral data and to support a 13-week GLP DRF study for repeated topical application in rats, comparing oral administration with 4 topical formulations. The DBS method was validated and demonstrated robustness and reproducibility for application to the DRF study. The assay results were comparable to a previously reported plasma LC/MS/MS assay-derived pharmacokinetic profile and provided justification for selection of the topical formulation and dose levels for the subsequent dermal carcinogenicity study.

Comparison of oral and transdermal administration of rasagiline mesylate on human melanoma tumor growth in vivo.

BACKGROUND/AIMS: Transdermal patch administration results in a locally high concentration of drug that induce local toxicity, including tumorogenicity. As a worst-case scenario for consequences of repeated application on neoplastic growth, the melanin-binding drug, rasagiline, was used in a transdermal formulation applied directly to a human-derived melanoma to determine the effects on tumor growth. MATERIALS AND METHODS: Rasagiline mesylate was administered either orally or transdermally to athymic mice implanted with human melanoma (SKMEL28) to determine the effects on tumor growth and survival. Over a 21-day period, animals were administered daily oral gavage (15 mg/kg) or one or two rasagiline mesylate transdermal patches every 3 days. After the last dose administration, blood samples were collected to confirm drug exposure. RESULTS: All animals from the untreated, vehicle and rasagiline groups survived to the end of the study; however, 7 out of the 10 cisplatin-treated animals died before the end of the study. Rasagiline mesylate dosed either via the oral or transdermal routes had comparable plasma exposure and, unexpectedly, significantly reduced absolute tumor volumes and tumor growth rates in the nude mouse SKMEL28 xenograft model. CONCLUSION: Transdermal delivery of melanin-binding rasagiline does not increase melanoma growth in the xenograft model. Because rasagiline decreases melanoma growth, it may be candidate for combination therapy for melanoma.