Acyclovir skin depot characterization following in vivo iontophoretic delivery

BACKGROUND/PURPOSE: Current Herpes labialis infection treatment by oral, parenteral or topical routes is inefficient. The objective of this study was to investigate the use of iontophoresis for improved topical delivery of acyclovir (ACV) in vivo in hairless rat. METHODS: Iontophoresis was performed for 10 min using a 5% ACV gel formulation. Tape stripping and skin extractions were performed at different time points following treatment for drug quantification in stratum corneum (SC) and underlying skin, respectively. RESULTS: Fourfold more ACV was detected in the SC immediately following 10-min iontophoresis as compared with passive delivery. Similarly, high ACV levels (29.27±3.52 μg/cm(2)) were achieved in the underlying skin following a single 10-min iontophoretic treatment while no drug detected following passive delivery (P<0.05). At 24-h post-iontophoresis, ACV levels in the SC decreased with a corresponding increase in the underlying skin due to drug migration. After 24-h post-iontophoresis, drug levels gradually decreased in both skin compartments until no ACV was detected at 72-h post-iontophoresis. CONCLUSION: Iontophoretic delivery of ACV resulted in high drug levels in skin layers to form a drug depot, which persisted over 2-3 days.