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Commentary on “Simultaneous Determination of Sildenafil and Glimepiride in Rat Plasma by Using LC-MS Method and their Applications in Pharmacokinetic Interactions”


Dr. Laura Green, Dr. Henry Ford


Department of Pharmaceutical Sciences, Example University


Dr. Laura Green, Department of Pharmaceutical Sciences, Example University, [City, Country]


The research article by Eyad Mallah and colleagues (2014) represents a significant contribution to the field of pharmacokinetics by developing a validated LC-MS method for simultaneous determination of sildenafil and glimepiride in rat plasma. The study is particularly relevant as it explores the pharmacokinetic interactions between these drugs, which are metabolized via cytochrome P450 systems in the liver. However, there are several aspects of the study that warrant further discussion and elucidation to enhance the interpretation and applicability of the findings.

Firstly, the choice of clarithromycin as an internal standard is both interesting and somewhat unconventional for this type of analysis. Clarithromycin is known to inhibit cytochrome P450 3A4, the same enzyme that metabolizes sildenafil. Although the authors mention the use of clarithromycin, they do not provide a justification for its selection over other potentially non-interacting internal standards. The interaction of clarithromycin with the metabolism of sildenafil could influence the pharmacokinetic parameters measured, potentially confounding the results. A discussion on the rationale for this choice and its implications on the study outcomes would be beneficial.

Secondly, the significant decrease in plasma concentrations of sildenafil when co-administered with glimepiride, as reported in the study, suggests a notable pharmacokinetic interaction. However, the mechanisms underlying these interactions are not thoroughly explored. It is hypothesized that competitive metabolism via the cytochrome P450 system may be involved, yet detailed enzymatic studies or inhibition assays would be instrumental in confirming this mechanism. Future studies could benefit from incorporating such assays to delineate the pathways of interaction more clearly.

Furthermore, while the study robustly demonstrates the application of the LC-MS method in analyzing these interactions in a rat model, the translation of these findings to clinical settings involves several complexities. The pharmacokinetic profiles in humans can differ significantly from those in rats due to variations in enzyme activity, expression levels, and overall metabolism. Thus, while the study lays a good foundation, caution should be exercised when extrapolating these results to human subjects. Clinical trials or studies using human liver microsomes could provide additional insights and validation of these interactions in humans.

Lastly, the study presents a wealth of data on the pharmacokinetics of both drugs, yet the discussion section could be expanded to include potential clinical implications or therapeutic concerns arising from these interactions. For example, the lowered efficacy of sildenafil when administered with glimepiride could have significant implications for patients who are prescribed both medications. Discussing possible clinical strategies to mitigate such interactions would be highly relevant and valuable to healthcare professionals.


The article by Mallah et al. is a commendable attempt to address a complex area of pharmacokinetics with significant clinical implications. While the study is methodologically sound, the discussion of certain key aspects such as the choice of internal standard, the detailed mechanism of drug interactions, and the clinical translation of the findings could be enhanced. Addressing these points in future research would undoubtedly strengthen the understanding and management of drug interactions between sildenafil and glimepiride.


  1. Mallah E, Al Ani N, Qinna N, Awad R, et al. (2014) Simultaneous Determination of Sildenafil and Glimepiride in Rat Plasma by Using Lc-Ms Method and their Applications in Pharmacokinetic Interactions. J Clin Pharm 1(2): 1007.