Simple high-performance liquid chromatographic method for the analysis of 9-(2-hydroxyethoxymethyl)guanine (acyclovir) in human plasma and urine.

Acyclovir, a new antiviral drug for human use, could not be solvent extracted and was retained poorly by reversed-phase (RP) columns. Drug in urine and plasma (deproteinised) could be chromatographed successfully as an ion-pair (with heptanesulphonic acid) on RP-18 columns. The validated method had the required sensitivity for a wide variety of clinical situations including metabolic and pharmacokinetic studies.