Short CommunicationSimultaneous determination of sildenafil citrate and some nitric oxide releasing drugs in human plasma using UPLC MS/MS
Graphical abstract
Simultaneous administration of sildenafil and nitric oxide releasing compounds (NRCs) is contraindicated as it may result in severe hypotension. NRCs include nicorandil, used to treat angina, and l-arginine rich foods. This paper describes an LC–MS/MS method for the simultaneous determination of sildenafil and some NO releasing compounds in human plasma. This method may be useful for assessing synergistic effects of drugs and foods that affect nitric oxide levels in patients with erectile dysfunction and angina.
Introduction
Sildenafil citrate (SLD), a selective inhibitor of the phosphodiesterase type 5 (PDE5), is an FDA-approved drug for erectile dysfunction (ED) [1]. Nicorandil (NRD) is a nicotinamide ester which acts as a NO donor, a β-blocker, and a calcium antagonist. It is used widely for treatment of stable angina [2]. ARG, a non/semi-essential amino acid, is abundant in many food supplements and a natural source of NO. It is used to aid treatments of heart and blood vessel conditions and as a male enhancing agents for ED [3].
Angina patients usually suffer ED; thus may receive male enhancing agents containing ARG, herbal medications adulterated with SLD, food products containing ARG, or over the counter SLD [4]. Co-administration of sildenafil and NO-rich compounds is contraindicated. When these two types of pharmacologic agents are co-administered inadvertently, cyclic guanosine monophosphate (cGMP) accumulates leading to marked vasodilatations and hypotension. The resulting hypotension may transform physiological angina from a reversible situation into an irreversible angina (Fig. 1) [4].
Several methods for individual analysis of SLD, NRD and ARG in plasma have been reported which have high sensitivity but are lengthy and incapable of simultaneous determination of the three analytes [5], [6], [7], [8], [9], [10]. This study describes a new UPLC–MS/MS method with small sample size (10 μL), short runtime (4 min) and easy sample preparation steps for the simultaneous determination of SLD, NRD, and ARG.
Section snippets
Materials and methods
SLD, NRD, and pregapalin (PRG) were obtained from NODQCAR (Egypt). Methanol, acetonitrile (HPLC grade), formic acid, acetic acid, ammonium acetate, tri-fluoroacetic acid (TFA) and ARG were purchased from Sigma-Aldrich (Germany). Millipore deionized (DI) water was used throughout the experiment. All other reagents were analytical grade. Human plasma was purchased from VACSERA (Egypt) and contained ARG of 3.84 μg/mL.
Acquity UPLC–MS/MS equipped with UPLC BEH C18 column (5 mm × 2.1 mm; 1.7 μm) and
Results and discussion
Selected transitions for MRM were 475.33 > 57.97 m/z, 212.02 > 136.05 m/z, 175.02 > 70.05 m/z and 159.89 > 55 m/z for SLD, NRD, ARG and PRG; respectively. The optimal scanning conditions are displayed in Table 1. The 3 drugs and the IS were separated at 2.85, 0.85, 0.45 and 0.62 min for SLD, NRD, ARG and PRG, respectively using gradient elution (Fig. 2).
The developed method was valid in terms of linearity (10–900 ng/mL for SLD and NRD while in range 1–30 μg/mL for ARG) in plasma based calibration curve. The
Conclusions
The developed LC–MS/MS method can be used for accurate and simultaneous determination of SLD, NRD, and ARG. The method can also be applied for the bioequivalence studies of SLD and NRD and other pharmacological studies to determine the safety margins for drug combinations. It may be also applied in health care/emergency settings to manage patients suspected of receiving combinations of SLD, NRCs, and/or arginine-rich foods.
Acknowledgment
This work has been funded by a grant from Yousef Jameel Science & Technology Research Center, School of Sciences & Engineering, AUC to Prof. Hassan Azzazy.
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