Separation methods for acyclovir and related antiviral compounds

Acyclovir (ACV) is an antiviral drug, which selectively inhibits replicatio n of members of the herpes group of DNA viruses with low cell toxicity. Val aciclovir (VACV), a prodrug of ACV is usually preferred in the oral treatme nt of viral infections, mainly herpes simplex virus (HSV). Also other analo gues such as ganciclovir and penciclovir are discussed here. The former act s against cytomegalovirus (CMV) in general and the latter against CW retini tis. The action mechanism of these antiviral drugs is presented briefly her e, mainly via phosphorylation and inhibition of the viral DNA polymerase. T he therapeutic use and the pharmacokinetics are also outlined. The measurem ent of the concentration of acyclovir and related compounds in biological s amples poses a particularly significant challenge because these drugs tend to be structurally similar to endogenous substances. The analysis requires the use of highly selective analytical techniques and chromatography method s are a first choice to determine drug content in pharmaceuticals and to me asure them in body fluids. Chromatography can be considered the procedure o f choice for the bio-analysis of this class of antiviral compounds, as this methodology is characterised by good specificity and accuracy and it is pa rticularly useful when metabolites need to be monitored. Among chromatograp hic techniques, the reversed-phase (RP) HPLC is widely used for the analysi s. C-18 Silica columns from 7.5 to 30 cm in length are used, the separation is carried out mainly at room temperature and less than 10 min is sufficie nt for the analysis at 1.0-1.5 ml/min of flow-rate. The separation methods require an isocratic system, and various authors have proposed a variety of mobile phases. The detection requires absorbance or fluorescence measureme nts carried out at 250-254 nm and at lambda (ex) = 260-285 nm, lambda (em) = 375-380 nm, respectively. The detection limit is about 0.3-10 ng/ml but t he most important aspect is related to the sample treatment, mainly when bo dy fluids are under examination. The plasma samples obtained from human blo od are pre-treated with an acid or acetonitrile deproteinization and the su pernatant after centrifugation is successively extracted before RP-HPLC inj ection. Capillary Electrophoresis methods are also discussed. This new anal ytical approach might be the expected evolution, in fact the analyses are i mproved with regard to time and performance, in particular coated capillary as well as addition of stabilisers have been employed. The time of analysi s is shortened arriving at less than half a minute. Furthermore by using an electrochemical detection, and having a calibration linearity in the range of 0.2-20.0 ng/ml, the detection limit is 0.15 mug/ml. The measurements of acyclovir arid penciclovir have been presented but in the future other rel ated drugs will probably be available using CE methods. (C) 2001 Elsevier S cience B.V. All rights reserved.