Controlled ex‐vivo plasma hydrolysis of valaciclovir to acyclovir demonstration using tandem mass spectrometry

Abstract

Plasma estimation of valaciclovir, an antiviral drug, is challenging due to both in-vivo and ex-vivo hydrolysis to active metabolite acyclovir. A simultaneous method is described involving the solid-phase ion-exchange extraction procedure requiring 100 μL of plasma volume, a reverse-phase Lichrosphere RP Select B (125 × 6 mm, 5 μm) column and isocratic mobile phase to achieve the desired chromatographic separation. ESI-MS/MS multiple reaction monitoring in positive polarity, detected mass pairs for valaciclovir (m/z 325.5 → 152.2), acyclovir (m/z 226.3 → 152.2) and respective internal standards valganciclovir (m/z 307.1 → 220.3) and acyclovir-d4 (m/z 230.2 → 152.0). Fully fledged method validation was evaluated as per current regulatory requirements and results were deemed acceptable. The plasma samples showed extensive hydrolysis of valaciclovir when collected or processed at room temperature, without buffer stabilization prior to storage at -15°C. Our results showed that using prechilled K3 EDTA vacutainers immersed in an iced-water bath during blood sample collection, and addition of 50% orthophosphoric acid solution to plasma samples prior to storage at -50°C for at least 120 days controlled the hydrolysis of valaciclovir to acyclovir. While monitoring drug absorption into systematic circulation, the valaciclovir to acyclovir formation ratio was improved to 1:20 in healthy volunteers for the first time.

A liquid chromatography/electrospray ionization tandem mass spectrometric method for quantification of asiatic acid from plasma: application to pharmacokinetic study in rats

“…The Matrix Factor (MF) was determined by comparing the peak area response of analyte and IS obtained from the extracted sample against the peak area response of analyte and IS of neat solutions. The value of MF = 1 denotes no matrix effect, MF <0.8 indicates ion suppression, while MF >1.2 signifies ion enhancement …”

Fast Determination of Ingredients in Solid Pharmaceuticals by Microwave-Enhanced In-Source Decay of Microwave Plasma Torch Mass Spectrometry

“…Both the protonated molecular ion m/z 226 and fragment ion m/z 152 of acyclovir can be observed in the full-scan mass spectrum obtained by the present simple TOF mass spectrometer, as shown in Figure 5f . Meanwhile, information of the fragment ion can be proven by the data from literatures [ 35 , 36 ] and MS n spectrum by MPT-LTQ MS (Supplementary Figure S-1f ). The fragment pathway (Supplementary Figure S-2f ) can be speculated that protonated acyclovir loses a methanal to form the ion at m/z 196.…”

Liquid chromatography–tandem mass spectrometry method for the estimation of adefovir in human plasma: Application to a pharmacokinetic study

“…Bioequivalence was established with Hepsera ® 10 mg adefovir tablets and pharmacokinetic parameters were similar to that of the monograph on innovator [13] based on our improved method. This method has been extensively validated like our previous method validation reported [14] , [15] , catering to the requirement of global regulatory agencies like USFDA and EMA. Moreover, the ISR at the end of the study further added strength to our current method.…”