Separation methods for acyclovir and related antiviral compounds

Pharmacokinetics and analytical determination of acyclovir in Asian elephant calves (Elephas maximus)

•

Pharmacokinetic and bioavailability data of acyclovir following intravenous and oral administration are reported for Asian elephant calves.

•

Data represent the first comprehensive LC-MS/MS analysis of plasma acyclovir concentrations after i.v. and oral administration in elephants.

A therapeutic regimen that includes antiviral drugs is critical for the survival of Asian elephant (Elephas maximus) calves infected with elephant endotheliotropic herpesvirus hemorrhagic disease (EEHV-HD), with acyclovir showing considerable promise. The purpose of this study was to determine the pharmacokinetics and bioavailability of acyclovir following intravenous (IV) and oral (PO) administration in Asian elephants. A single dose of acyclovir (15 mg/kg, IV or 45 mg/kg, PO) was administered to four healthy elephant calves, with a minimum 2-week washout period between treatments. Serial plasma samples were collected after each injection for acyclovir analysis using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique. Maximum plasma acyclovir concentrations were 27.02 ± 6.79 µg/mL at 0.94 ± 0.31 h after IV administration, and 1.45 ± 0.20 µg/mL at 3.00 ± 0.70 h after PO administration. The half-life of the elimination phase (T_1/2) was 5.84 ± 0.74 and 8.74 ± 2.47 h after IV and PO administration, respectively. After IV administration, acyclovir concentrations were higher than the half-maximal inhibitory concentration (IC₅₀) of those found for herpes simplex virus (HSV) 1 and 2 in humans, and equid alpha herpesvirus-1 (EHV-1) for at least 12 h. By contrast, the bioavailability of oral administration was low, only 6.03 ± 0.87%, so higher doses by that route likely are needed to be effective. Due to the high concentration of plasma acyclovir after IV administration, the dose may need to be adjusted to prevent any negative side effects.

Screening and application of a broad-spectrum aptamer for acyclic guanosine analogues

Acyclic guanosine analogues, a class of widely used antiviral drugs, can cause chronic toxicity and virus resistance. Therefore, it is essential to establish rapid and accurate methods to detect acyclic guanosine analogues. In this study, five acyclic guanosine analogues (acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir) were used as positive targets to obtain broad-spectrum aptamers through Capture-SELEX technology. Real-time quantitative PCR (Q-PCR) was used to monitor the aptamer SELEX process. After the sixteen rounds of selection against mixed targets, sequences were obtained by high-throughput sequencing (HTS). Furthermore, a broad-spectrum aptamer, named CIV6, was found as the higher performance aptamer that was suitable for five acyclic guanosine analogues by graphene oxide (GO) polarization and fluorescence assay. Finally, the aptamer CIV6 was used to construct GO fluorescence assay to detect five acyclic guanosine analogues. The limits of detection (LOD) of acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir were 0.48 ng·mL^-1, 0.53 ng·mL^-1, 0.50 ng·mL^-1, 0.56 ng·mL^-1, and 0.38 ng·mL^-1, respectively.

Detection and quantification of Covid-19 antiviral drugs in biological fluids and tissues

Since coronavirus disease 2019 (COVID-19) started as a fast-spreading pandemic, causing a huge number of deaths worldwide, several therapeutic options have been tested to counteract or reduce the clinical symptoms of patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific drugs for COVID-19 are available, but many antiviral agents have been authorised by several national agencies. Most of them are under investigation in both preclinical and clinical trials; however, pharmacokinetic and metabolism studies are needed to identify the most suitable dose to achieve the desired effect on SARS-CoV-2. Therefore, the efforts of the scientific community have focused on the screening of therapies able to counteract the most severe effects of the infection, as well as on the search of sensitive and selective analytical methods for drug detection in biological matrices, both fluids and tissues. In the last decade, many analytical methods have been proposed for the detection and quantification of antiviral compounds currently being tested for COVID-19 treatment. In this review, a critical discussion on the overall analytical procedure is provided, i.e (a) sample pre-treatment and extraction methods such as protein precipitation (PP), solid-phase extraction (SPE), liquid-liquid extraction (LLE), ultrasound-assisted extraction (UAE) and QuEChERS (quick, easy, cheap, effective, rugged and safe), (b) detection and quantification methods such as potentiometry, spectrofluorimetry and mass spectrometry (MS) as well as (c) methods including a preliminary separation step, such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) coupled to UV-Vis or MS detection. Further current trends, advantages and disadvantages and prospects of these methods have been discussed, to help the analytical advances in reducing the harm caused by the SARS-CoV-2 virus.

High Throughput Screening of Valganciclovir in Acidic Microenvironments of Polyester Thin Films

Ganciclovir and valganciclor are antiviral agents used for the treatment of cytomegalovirus retinitis. The conventional method for administering ganciclovir in cytomegalovirus retinitis patients is repeated intravitreal injections. In order to obviate the possible detrimental effects of repeated intraocular injections, to improve compliance and to eliminate systemic side-effects, we investigated the tuning of the ganciclovir pro-drug valganciclovir and the release from thin films of poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), or mixtures of both, as a step towards prototyping periocular valganciclovir implants. To investigate the drug release, we established and evaluated a high throughput fluorescence-based quantification screening assay for the detection of valganciclovir. Our protocol allows quantifying as little as 20 ng of valganciclovir in 96-well polypropylene plates and a 50× faster analysis compared to traditional HPLC measurements. This improvement can hence be extrapolated to other polyester matrix thin film formulations using a high-throughput approach. The acidic microenvironment within the polyester matrix was found to protect valganciclovir from degradation with resultant increases in the half-life of the drug in the periocular implant to 100 days. Linear release profiles were obtained using the pure polyester polymers for 10 days and 60 days formulations; however, gross phase separations of PCL and acid-terminated PLGA prevented tuning within these timeframes due to the phase separation of the polymer, valganciclovir, or both.

Determination of ganciclovir in human plasma by ultra performance liquid chromatography-UV detection

OBJECTIVES

Implement a sensitive UHPLC method for the assay of ganciclovir in human plasma.

DESIGN AND METHODS

We developed and validated a chromatographic method coupled to ultraviolet detection for quantification of ganciclovir, with a short run time using a small volume of human plasma. Comparison of system performance was made with respect to analysis time, efficiency and sensitivity.

RESULTS

Correlation coefficients (r) of the calibration curves ranged from 0.999744 to 0.999784. Within-day and between-day imprecision and inaccuracy, specificity and recovery were also evaluated for validation. The method was precise and accurate and the retention time was 0.7 min. The calibration curves were linear between 0.5 and 30 μg/mL. There was a good correlation between HPLC and UHPLC techniques.

CONCLUSIONS

We developed a method that is currently applied in a clinical study assessing GCV plasma concentration variability after ganciclovir and valganciclovir administration.

Multispectroscopic studies of the interaction of calf thymus DNA with the anti-viral drug, valacyclovir

The present study investigated the binding interaction between an antiviral drug, valacyclovir and calf thymus DNA (CT-DNA) using emission, absorption, circular dichroism, viscosity and DNA melting studies. In fluorimetric studies, thermodynamic enhancement constant (K(D)) and bimolecular enhancement constant (K(B)) were calculated at different temperatures and demonstrated that fluorescence enhancement is not initiated by a dynamic process, but instead by a static process that involves complex DNA formation in the ground state. Further, the enthalpy and entropy of the reaction between the drug and CT-DNA showed that the reaction is exothermic and enthalpy-favored. In addition, detectable changes in the circular dichroism spectrum of CT-DNA in the presence of valacyclovir indicated conformational changes in the DNA double helix following interaction with the drug. All these results prove that this antiviral drug interacts with CT-DNA via an intercalative mode of binding.

Lack of a pharmacokinetic interaction between steady-state tipranavir/ritonavir and single-dose valacyclovir in healthy volunteers

OBJECTIVE

This study assessed the single-dose pharmacokinetics of the herpes antiviral acyclovir (administered as the pro-drug valacyclovir) alone and in combination with twice-daily 200 mg ritonavir-boosted tipranavir (500 mg) at steady state.

METHODS

The study was an open label, one-sequence cross-over pharmacokinetic study in HIV-negative adults. Plasma drug concentrations were measured by validated LC/MS/MS assays; pharmacokinetics (AUC, C(max)) were determined using noncompartmental methods. The geometric mean ratio and 90% confidence interval [GMR, 90% CI] were used to evaluate the drug interaction.

RESULTS

Twenty-six of 29 subjects completed the trial. With steady-state tipranavir/ritonavir, acyclovir C(max) decreased 4.9% [0.95, 0.88-1.02] and AUC increased 6.6% [1.07, 1.04-1.09]. The majority of subjects experienced at least one adverse event, most of which were mild gastrointestinal disorders. Three subjects discontinued tipranavir/ritonavir treatment as a result of drug-related increases in ALT/AST, including one subject who experienced mild upper abdominal pain. All subjects recovered without sequelae.

CONCLUSIONS

When administered as a single dose of valacyclovir with steady-state tipranavir/ritonavir, there were no clinically important changes in acyclovir pharmacokinetics. This result indicates that valacyclovir can be co-administered safely with no dose adjustments.

Chromatographic separation of antiviral/anticancer nucleoside reverse transcriptase inhibitor drugs

This paper discusses the current methods used for quantitative determination of analogues of nucleotide reverse transcriptase inhibitors (NtRTIs) in body fluids, cells, and tissues. Nucleoside reverse transcriptase inhibitors (NRTIs) prodrugs given to AIDS/herpes/cancer patients conjugate with phosphates at the site of their action. Separation of phosphorylated NRTIs is generally performed by reversed-phase chromatography. After separation, plasma NRTIs can be detected using a variety of methods, including immunoassay through monitoring of UV absorbance, fluorescence, and mass spectrometry. The most recent development in the field of detection of plasma NtRTIs shows a tendency toward the use double- or triple-focusing mass spectrometry, the most specific and sensitive monitoring technique.

Long-term impact of acyclovir suppressive therapy on genital and plasma HIV RNA in Tanzanian women: a randomized controlled trial

BACKGROUND

Herpes simplex virus (HSV) suppressive therapy reduces genital and plasma human immunodeficiency virus type 1 (HIV-1) RNA over periods up to 3 months, but the long-term effect is unknown.

METHODS

A total of 484 HIV-1 and HSV type 2 seropositive Tanzanian women aged 16-35 years were enrolled in a randomized placebo-controlled trial of acyclovir administered at a dosage of 400 mg twice daily. Cervico-vaginal lavage and blood samples were collected at 6 months, 12 months, and 24 months for quantification of genital and plasma HIV-1 RNA and genital HSV DNA. Primary outcomes were detection and quantity of cervico-vaginal HIV-1 RNA at 6 months.

RESULTS

At 6 months, there was little difference between the acyclovir and placebo arms for cervico-vaginal HIV-1 RNA detection (88 [ 41 .3%] of 213 vs 84 [ 44 .0%] of 191; odds ratio [OR], 0.90; 95% confidence interval [CI], 0.60-1.33), HSV DNA detection (20 [ 9 .4%] of 213 vs 22 [ 11 .5%] of 191; OR, 0.80; 95% CI, 0.42-1.51), genital HIV or HSV loads, or plasma HIV-1 RNA load. Estimated median adherence was 91%. There was a suggestion of an impact on cervico-vaginal HIV-1 RNA detection among women with estimated adherence 90% (OR, 0.74; 95% CI, 0.50-1.09) when data from all 3 visits were included.

CONCLUSIONS

Acyclovir administered at a dosage of 400 mg twice daily is unlikely to be a useful long-term intervention to reduce HIV transmission. The lack of effect on HIV may be attributable to suboptimal adherence or treatment regimen.

Assay and stability-indicating micellar electrokinetic chromatography method for the simultaneous determination of valacyclovir, acyclovir and their major impurity guanine in pharmaceutical formulations

A micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of the antiviral drugs acyclovir and valacyclovir and their major impurity, guanine, was developed. The influences of several factors (surfactant and buffer concentration, pH, applied voltage, capillary temperature and injection time) were studied. Using tyramine hydrochloride as internal standard, the analytes were all separated in about 4 min. The separation was carried out in reversed polarity mode at 28 degrees C, 25 kV and using hydrodynamic injection (15 s). The separation was effected in a fused-silica capillary 100 microm x 56 cm and a background electrolyte of 20 mM citric acid-1 M Tris solution (pH 2.75), containing 125 mM sodium dodecyl sulphate and detection at 254 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 0.1-1 microg/mL (guanine) and from 0.1 to 120 microg/mL for both valacyclovir and acyclovir. The relative standard deviations of intra- and inter-day migration times and corrected peak areas were less than 5.0%. The proposed method was successfully applied to the determination of the analytes in tablets and creams. From the previous study it is concluded that the stability-indicating method developed for acyclovir and valacyclovir can be used for analysis of the drug in various stability samples.

Measurement and predictors of adherence in a trial of HSV suppressive therapy in Tanzania

This study estimates adherence and identifies predictors of good adherence among 1305 Tanzanian women participating in a randomised, double-blind, placebo-controlled trial of HSV suppressive therapy to reduce HIV incidence or genital HIV shedding. Women were randomised to acyclovir 400mg BD or placebo and followed every three months for 12-30 months. Adherence was assessed by tablet counts. Random urine samples, collected between 6 and 24 months, were tested for acyclovir. At 12, 24 and 30 month visits, 56%, 52% and 54% of women on treatment had adherence >or=90%, respectively. Factors independently associated with good adherence (taking >or=90% of tablets in the preceding 3-months) included older age, understanding trial concepts at enrolment, living >2 years in the screening site, receiving an unannounced tablet check visit, using oral contraception at screening, living in the same site and house as the previous visit, accessing VCT during the trial, recent malaria and not having a positive pregnancy test. Overall, 55% of urine samples from women randomised to acyclovir had detectable acyclovir. Additional, tailored adherence strategies may be needed for younger, more mobile women and those who have not used oral contraception, which may sensitise them to daily tablet-taking. Use of biomarkers may alert investigators to adherence problems.

Effect of herpes simplex suppression on incidence of HIV among women in Tanzania

BACKGROUND

Infection with herpes simplex virus type 2 (HSV-2) is associated with an increased risk of acquiring infection with the human immunodeficiency virus (HIV). This study tested the hypothesis that HSV-2 suppressive therapy reduces the risk of HIV acquisition.

METHODS

Female workers at recreational facilities in northwestern Tanzania who were 16 to 35 years of age were interviewed and underwent serologic testing for HIV and HSV-2. We enrolled female workers who were HIV-seronegative and HSV-2-seropositive in a randomized, double-blind, placebo-controlled trial of suppressive treatment with acyclovir (400 mg twice daily). Participants attended mobile clinics every 3 months for a follow-up period of 12 to 30 months, depending on enrollment date. The primary outcome was the incidence of infection with HIV. We used a modified intention-to-treat analysis; data for participants who became pregnant were censored. Adherence to treatment was estimated by a tablet count at each visit.

RESULTS

A total of 821 participants were randomly assigned to receive acyclovir (400 participants) or placebo (421 participants); 679 (83%) completed follow-up. Mean follow-up for the acyclovir and placebo groups was 1.52 and 1.62 years, respectively. The incidence of HIV infection was 4.27 per 100 person-years (27 participants in the acyclovir group and 28 in the placebo group), and there was no overall effect of acyclovir on the incidence of HIV (rate ratio for the acyclovir group, 1.08; 95% confidence interval, 0.64 to 1.83). The estimated median adherence was 90%. Genital HSV was detected in a similar proportion of participants in the two study groups at 6, 12, and 24 months. No serious adverse events were attributable to treatment with acyclovir.

CONCLUSIONS

These data show no evidence that acyclovir (400 mg twice daily) as HSV suppressive therapy decreases the incidence of infection with HIV. (Current Controlled Trials number, ISRCTN35385041 [controlled-trials.com].).

Development and validation of a high-performance liquid chromatography–tandem mass spectrometry for the determination of penciclovir in human plasma: Application to a bioequivalence study

We developed and validated a simple high-performance liquid chromatography (HPLC) coupled with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection system for determining penciclovir (active metabolite of famciclovir) levels in human plasma using acyclovir as an internal standard (IS). Acquisition was performed in multiple reaction monitoring (MRM) mode by monitoring the transitions: m/z 254.00>152.09 for penciclovir and m/z 226.00>152.09 for IS. The analytes were chromatographed on a Capcellpak MGII C(18) reversed-phase chromatographic column by isocratic elution using 30% methanol and 70% Milli-Q water containing 10 mM ammonium formate (adjusted to pH 3.1 with formic acid). Results were linear over the studied range (0.05-10 microg/ml) with r(2)=0.9999, and the total analysis time for each run was 2 min. Intra- and inter-assay precisions were 2.3-7.8 and 3.7-7.5%, respectively, and intra- and inter-assay relative errors (RE) were 2.0-8.4 and 1.9-9.1%, respectively. The lower limit of quantification (LLOQ) was 0.05 microg/ml. At this concentration mean intra- and inter-assay precisions were 7.8 and 7.5%, respectively, and mean intra- and inter-assay relative errors were 2.2 and 9.1%, respectively. Penciclovir was found to be stable in plasma samples under short-, long-term storage and processing conditions. The developed assay was successfully applied to a bioequivalence study of penciclovir administered as a single oral dose (500 mg as famciclovir) to healthy volunteers.

Valganciclovir for congenital CMV infection: a pilot study on plasma concentration in newborns and infants

The pharmacokinetics of valganciclovir were studied in 8 infants ranging in age from 4 to 90 days (mean 20 days). We suggest that doses of 15 mg/kg given twice daily may be suitable for neonates and young infants.

Determination of ganciclovir in different matrices from solid organ transplanted patients treated with a wide range of concomitant drugs

The aim of the present study was to develop a time-efficient chromatographic method for the analysis of therapeutic concentrations of ganciclovir (GCV) in plasma, urine as well as dialysate (from continuous renal replacement therapy) from solid organ transplant recipient treated with either GCV or its prodrug valganciclovir (VGCV) in combination with a wide variety of other concomitant drugs. Sample preparation was performed by reversed phase solid phase extraction and was followed by separation of the analytes on a reversed phase column using isocratic elution with a mobile phase consisting of acetonitrile-a counter ion (50 mM 1-heptanesulfonic acid) in an aqueous sodium dihydrogen phosphate buffer (pH 2.1; 10 mM) (10:90 v/v) and a fluorescence detector. Validation of the method showed linearity within the concentration range of 0.1-40 microg/mL for plasma and 0.1-120 microg/mL for urine and dialysate (R(2)>0.99, n> or =5). Accuracy and precision (evaluated at 0.1, 5 and 40 microg/mL) were both satisfactory. The LLOQ was determined to be 0.1 microg/mL. The method was successfully applied on clinical samples from renal transplant recipients treated with VGCV in combination with a variety of usually used concomitant drugs for solid organ transplant recipients.

Effect of Hydroxylic Solvent on the Fluorescence Behavior of Some Bioactive 9-Oxo-imidazo[1,2-a]purine Derivatives

The spectral and photophysical behavior of four fluorescent 9-oxo-imidazo[1,2-a]purine derivatives containing pyridyl, pyridylphenyl, phenyl, and biphenylyl substituents at the C(6) position of the tricyclic skeleton is described. The studies were performed in several aprotic and protic organic solvents using absorption spectroscopy as well as steady-state and time-resolved fluorescence spectroscopy. The results are also presented of TDDFT calculations on singlet-singlet excitation energies and oscillator strengths for two models of 9-oxo-imidazo[1,2-a]purine, with phenyl or pyridyl substituents, both in the gas phase and in methanol solution. While the derivatives with aryl substituents did not show any significant dependence of their static and dynamic fluorescence properties on the nature of the solvent, the compounds containing a pyridine residue exhibited a remarkable reduction of their fluorescence quantum yields and lifetimes in the alcoholic solutions. The solute-solvent hydrogen-bonding interaction in the first excited singlet state is responsible for the fast radiationless decay rates determined for pyridyl- and pyridylphenyl-substituted compounds in protic solvents. The results of experimental and theoretical studies show that the hydrogen of the alcohols' hydroxyl group and the nitrogen atom of the pyridine moiety are involved in the interaction. The fluorescence-quenching experiments performed for the pyridyl-substituted 9-oxo-imidazo[1,2-a]purine derivative using trifluoroethanol, methanol, and butanol as quenchers revealed that the quenching efficiencies, expressed by the Stern-Volmer quenching constants, correlate with the H-bond donating abilities of the alcohols. The quenching is a dynamic process, and the H-bonded complex formed is nonfluorescent. The experimentally determined and the calculated values of the dipole moment change associated with the electronic excitation indicate that the excited S(1) states of all of the molecules studied in this work have an intramolecular charge-transfer character and that electronic charge is transferred to the C(6) substituent upon excitation. Thus, the ability of the pyridyl substituent nitrogen atom to act as an H-bond acceptor in the excited S(1) state is enhanced. The 6-pyridyl-9-oxo-imidazo[1,2-a]purine presents a novel fluorophore, which, besides its medical applications, may be useful as a sensor of hydroxyl groups in microorganized systems.

Quantification of ganciclovir in human plasma using capillary electrophoresis

A fast, simple, specific capillary electrophoretic method in the MEKC mode for the quantification of the antiviral drug ganciclovir is described. The separation was obtained using a 50 microm id fused-silica capillary, 60 mM borax buffer (pH 9.25) containing 40 mM SDS using ethenoadenosine as the internal standard. Sample preparation was done by ultrafiltration with a Microcon 30 000 kDa filter. The analytes were detected with UV detector at 254 nm. A sufficient sensitivity was achieved by using a bubble cell capillary. The linear range was from 0.5 to 10 mg/L with a LOQ of 0.5 mg/L. Correlation coefficients were better than 0.999 whereas inter- and intraday precision and accuracy were less than 10.7%. The analysis of patients' samples after administration of ganciclovir indicates that the method is suitable for drug monitoring in the clinic.

High-performance liquid chromatographic determination of lamivudine in human serum using liquid–liquid extraction; application to pharmacokinetic studies

A simple, fast, and sensitive high performance liquid chromatographic (HPLC) assay was developed for quantitation of lamivudine in human serum. Lamivudine is polar compound and its extraction from the human serum in previously published HPLC methods involved either protein precipitation or solid phase extraction techniques. However, existence of endogenous peaks which interfere with the drug or appeared as late eluting peaks and lead to long run time of analysis has been reported. Application of either an ion pairing agent in the mobile phase or time consuming column purge has been used in the published methods. Present paper describes liquid - liquid extraction of lamivudine and internal standard (famotidine) using dichloromethane-isopropyl alcohol (1:1, v/v) as an extracting solvent and salting out approach. The mobile phase was a mixture of phosphate buffer (0.05 M) containing triethylamine (1 mL/L, v/v; pH 3.5) and methanol (91:9, v/v) at a flow rate of 2.2 mL/min. The analysis was performed on a column (150 mm x 6 mm i.d.) which was packed with 5 microm particles of ODS packing material. Under these conditions no interference in the assay from any endogenous substance was observed. The limit of quantification was evaluated to be 5 ng/mL. Accuracy and precision of the method were also studied and the technique was shown to be selective and linear into the concentration range of 5-2500 ng/mL. This method has been used in two randomized crossover bioequivalence studies of 100 and 150 mg lamivudine preparations in 12 and 24 healthy volunteers, respectively.

Determination of acyclovir in human serum by high-performance liquid chromatography using liquid–liquid extraction and its application in pharmacokinetic studies

A fast, simple and sensitive high performance liquid chromatographic (HPLC) method has been described for determination of acyclovir in human serum. Since acyclovir is a polar compound and soluble in aqueous medium and practically insoluble in most of organic solvents, its analysis in biological fluids in currently published HPLC methods, involve pre-treatment of acyclovir plasma sample including deproteinization or solid phase extraction. In present method liquid-liquid extraction of acyclovir and internal standard (vanillin) is achieved using dichloromethane-isopropyl alcohol (1:1, v/v) as an extracting solvent. Analysis was carried out on ODS column using methanol-phosphate buffer (0.05 M) containing sodium dodecyl sulfate (200 mg/L) and triethylamine (2 mL/L, v/v) as mobile phase (pH=2.3; 5:95, v/v) at flow rate of 2 ml/min. The method was shown to be selective and linear into the concentration range of 10-2560 ng/mL. Accuracy and precision of the method were also studied. The limit of quantitation was evaluated to be 10 ng/mL. This method was applied in bioequivalence study of two different acyclovir preparations after administration of 400mg in 12 healthy volunteers.

Ganciclovir in solid organ transplant recipients: is there a role for clinical pharmacokinetic monitoring?

The authors use a previously published decision-making algorithm to address the role of clinical pharmacokinetic monitoring of ganciclovir, the drug of choice for prophylaxis and treatment of cytomegalovirus (CMV) in solid organ transplant recipients. Ganciclovir pharmacokinetics have been studied in solid organ transplant recipients with a wide range of peak and trough concentrations reported. Numerous assays are available to measure plasma concentrations of ganciclovir, but no clear correlation has been established between peak or trough concentrations and either efficacy or toxicity of the drug. For patients receiving treatment, the pharmacological response of ganciclovir is assessed initially by clinical response. Monitoring prophylactic therapy in asymptomatic patients poses a greater challenge. Although monitoring of antigenemia or polymerase chain reaction (PCR) deoxyribonucleic acid (DNA) is not yet part of routine clinical practice, studies have shown a role for these techniques in monitoring response to antiviral therapy. Studies of subpopulations of renal failure patients show a prolonged ganciclovir half-life that requires dosage adjustments. However, ganciclovir clearance is closely correlated with creatinine clearance, which is an appropriate approach to adjusting dosages. Studies in pediatric patients also demonstrate a close correlation between dose per kilogram and AUC, suggesting that monitoring of ganciclovir levels may not be necessary. Based on the evidence presented in this review, routine clinical pharmacokinetic monitoring of ganciclovir does not appear to be warranted in solid organ transplant recipients.

Technique validation by liquid chromatography for the determination of acyclovir in plasma

In this research project, a high-performance liquid chromatography (HPLC) method was developed for the determination of acyclovir (ACV) in plasma. The plasma samples, recharged with acyclovir and in presence of 5'-N-methylcarboxyamidoadenosine (MECA) as an internal standard, were purified using a solid-phase extraction technique with Waters Oasis HLB columns. The separation of the components from the extract was carried out in a LiChrospher 100 RP-18 column for further ultraviolet detection at a wavelength range of 250-260 nm. The mobile phase composition was 18% acetonitrile, sodium dodecylsulphate 5 mM and phosphate buffer at pH 2.6 with an analysis time of 13 min per sample. The average retention time for acyclovir was of 5.0 min and for the internal standard 11.2 min. The calibration curve was linear ranging between 0.05 and 1.80 microg/ml. The detection limit was 0.006 microg/ml with a quantification limit of 0.020 microg/ml. The ACV recuperation percentage for 250 microl of plasma was between 94.7 and 109.7% with a coefficient of variation not higher than 5.2%. This method was developed and validated for use in bioavailability and bioequivalence studies.

Hydrophilic interaction liquid chromatography/electrospray mass spectrometry determination of acyclovir in pregnant rat plasma and tissues

Reversed-phase chromatography is the most common means of separation for small drug molecules. However, polar drugs may suffer from poor retention and peak shape in reversed-phase high-performance liquid chromatography (RP-HPLC). Hydrophilic interaction liquid chromatography (HILIC) provides a viable alternative to RP-HPLC and is an excellent way to separate polar compounds. This paper describes a HILIC/ESI-MS/MS assay for the determination of acyclovir from rat plasma, amniotic fluid, placental tissue, and fetal tissue. The isocratic separation utilizes an underivatized silica column with an acetonitrile/formate buffer mobile phase (80:20). The method is validated over a range of 50 ng/mL to 50 micro g/mL with % error and % relative standard deviation of <15% over 3 days. All samples are prepared by acetonitrile protein precipitation, which yields high recovery (>84% for acyclovir). This assay can be applied to the pharmacokinetic study of the placental transfer of acyclovir.