Pharmacokinetics in Elderly Women of Benzyl Alcohol From an Oil Depot.

Pharmaceutical oil depots are meant to release active substances at a sustained rate. Most of these depots contain benzyl alcohol (BOH) to facilitate the production and administration. Because BOH changes the solubility of components in both the body fluid and the oil formulation, it is relevant to know the change in the BOH concentration in the oil over time. In this study, volunteers were subcutaneously injected with an oil depot that contained 10% BOH, nandrolone decanoate, and cholecalciferol. The aim of this study was to determine the pharmacokinetic profiles of BOH and its metabolites benzoic acid and hippuric acid simultaneously in serum to estimate the BOH release out of the depot. For this, an HPLC bioassay was developed and adequately validated. Hereafter, the bioassay was applied to serum samples obtained at several time points between 0 and 35 days. BOH appeared immediately in serum after injection. The pharmacokinetic profile revealed that all BOH was depleted from the depot within 52 h after injection. Thus, the partition coefficient of active substances between the oil formulation and the body tissue changes rapidly in the first days after injection but will remain constant hereafter.