['To investigate the topical iontophoresis of valaciclovir (VCV) as a means to improve cutaneous aciclovir (ACV) delivery.', 'ACV and VCV electrotransport experiments were conducted using excised porcine skin in vitro.', 'While the charged nature of the prodrug, VCV, enabled it to be more efficiently iontophoresed into the skin than the parent molecule, ACV, only the latter was detectable in the receptor chamber, suggesting that VCV was enzymatically cleaved into the active metabolite during skin transit. Iontophoresis of VCV was significantly more efficient than that of ACV; the cumulative permeation of ACV after 1, 2 and 3 h of VCV iontophoresis at 0.5 mA cm(-2) and using an aqueous 2 mM (approximately 0.06%) formulation was 20+/-10, 104+/-47 and 194+/- 82 microg cm( -2), respectively (cf. non-quantifiable levels, 0.1 and 1.0+/-0.7 microg cm(-2) after ACV iontophoresis).'] Does topical iontophoresis of valaciclovir hydrochloride improve cutaneous aciclovir delivery?