Rapid and sensitive liquid chromatography/tandem mass spectrometry method for simultaneous determination of enalapril and its major metabolite enalaprilat, in human plasma: Application to a bioequivalence study

Abstract

A rapid and most sensitive method for simultaneous determination of enalapril (ENP) and its metabolite, enalaprilat (ENPT), in human plasma using ESI-LC-MS/MS (electrospray ionization liquid chromatography tandem mass spectrometry) positive ion multiple reactions monitoring (MRM) mode, was developed and validated. The procedure involves a simple solid-phase extraction (SPE) followed by evaporation of the sample. Chromatographic separation was carried out on a Hypurity C(18) column (50 mm × 4.6 mm, 5 µm) with an isocratic mobile phase and a total run time of 2.0 min only. The MRM of ENP and ENPT is 377.10 → 234.20 and 349.20 → 206.10 respectively. The standard calibration curves showed excellent linearity within the range of 0.064 to 431.806 ng/mL for ENA and 0.064 to 431.720 ng/mL for ENPT (r ≥ 0.990). This is the only method which can quantitate upto 0.064 ng/mL for both ENP and ENPT in a single run with the shortest analysis time. In matrix effect experiment, this method shows a % CV (% coefficients of variation) of less than 5, which means that the proposed method is free from any kind of irregular ionization process. This method was successfully applied to a pharmacokinetic study after oral administration of enalapril maleate 20 mg tablet in Indian healthy male volunteers.

LC–MS/MS Assay for Quantitation of Enalapril and Enalaprilat in Plasma for Bioequivalence Study in Indian Subjects

“…ACE inhibitors such as EPL inhibit the conversion of angiotensin I to angiotensin II decreasing blood pressure and aldosterone secretion, slightly increasing serum potassium levels, and causing sodium and fluid loss. Also, increased prostaglandin synthesis is involved in the antihypertensive action [6–7,13,18–19]. …”

“…EPLT is the only metabolite of EPL [1,16,18,20–21]. It is a more potent and effective ACE inhibitor than EPL and is also effectively used in the treatment of hypertension and congestive heart failure through dilation of peripheral vascular resistance without causing any significant changes in heart rate or cardiac output [14,18,22]. After oral administration of EPL, maximum plasma concentration is reached within about 1 h [14,18,22–23].…”

“…In healthy subjects EPL is rapidly absorbed from the GI tract and bioavailability is about 60–70%. The terminal half-life of EPL is approximately 2 h [11,14,18,22–23]. The absorption of EPL after oral administration is not influenced by the presence of food in the GI tract [11,18].…”

“…The terminal half-life of EPL is approximately 2 h [11,14,18,22–23]. The absorption of EPL after oral administration is not influenced by the presence of food in the GI tract [11,18]. However, after 4 h it is not detected above 10 ng/ml [14,22].…”

“…However, after 4 h it is not detected above 10 ng/ml [14,22]. EPLT is detectable for upto 72 h and maximum plasma concentration is observed at approximately 3–4 h after administration with a half-life of approximately 30–35 h [14,18,22–23]. When administered orally, EPLT is poorly absorbed.…”