Simultaneous LC−UV Analysis of Mirodenafil and Its Two Main Metabolites in Rat Plasma and Urine, and in Tissue Homogenates

Pharmacokinetics of mirodenafil and its two metabolites, SK3541 and SK3544, in spontaneously or DOCA-salt-induced hypertensive rats

Hypertension is the most common comorbidity and major risk factor in patients with erectile dysfunction. The pharmacokinetics of mirodenafil, used for the treatment of erectile dysfunction, after the intravenous and oral administration (20 mg/kg) to 6-week-old rats (with blood pressure within the normotensive range) and 16-week-old spontaneously hypertensive rats (SHRs) and their age-matched control normotensive Kyoto-Wistar (KW) rats, and 16-week-old deoxycorticosterone acetate-salt-induced hypertensive rats (DOCA-salt rats) and their age-matched control Sprague-Dawley (SD) rats were compared. It was found that time-averaged renal clearance (Cl(r)) was of minor importance and that time-averaged non-renal clearance (Cl(nr)) was dominant. In both 6- and 16-week-old SHRs, the Cl(nr)s and areas under the curve (AUCs) of intravenous mirodenafil were significantly smaller and greater than those of the controls, but in 16-week-old DOCA-salt rats, they were comparable to the controls. Although the AUC of oral mirodenafil in 16-week-old SHRs was comparable to the controls, the Cl(nr)s (or total body clearances, Cls) of intravenous mirodenafil and intestinal intrinsic clearances were significantly smaller than the controls and comparable to the controls for both 6- and 16-week-old SHRs, unlike in the 16-week-old DOCA-salt rats. The above data suggest that the significantly smaller Cl(nr) and greater AUC of intravenous mirodenafil and comparable AUC of oral mirodenafil in 16-week-old SHR could be due to the hereditary characteristics of SHRs, and not due to the hypertensive state itself.

Faster clearance of mirodenafil in rats with acute renal failure induced by uranyl nitrate: contribution of increased protein expression of hepatic CYP3A1 and intestinal CYP1A1 and 3A1/2

Objectives

It has been reported that mirodenafil is primarily metabolized via hepatic cytochrome P450 (CYP) 1A1/2, 2B1/2, 2D1 and 3A1/2 in rats. It has also been reported that the protein expression of hepatic CYP3A1 and intestinal CYP1A1 and 3A1/2 increases and that of hepatic CYP2D1 decreases in rats with acute renal failure induced by uranyl nitrate (U-ARF rats). Thus, the pharmacokinetics of mirodenafil were studied in control and U-ARF rats.

Methods

The pharmacokinetic parameters of mirodenafil and SK3541 (a metabolite of mirodenafil) were compared after the intravenous and oral administration of mirodenafil at a dose of 20 mg/kg to U-ARF and control rats.

Key findings

After interavenous administration of mirodenafil to U-ARF rats, the total area under the concentration–time curve (AUC) of mirodenafil was significantly smaller (36.5% decrease) than controls, possibly due to the significantly faster non-renal clearance (66.1% increase; because of increase in the protein expression of hepatic CYP3A1) than controls. After the oral administration of mirodenafil to U-ARF rats, the AUC of mirodenafil was also significantly smaller (47.8% decrease) due to the increase in the protein expression of hepatic CYP3A1 and intestinal CYP1A1 and 3A1/2 compared with controls.

Conclusions

After both intravenous and oral administration of mirodenafil to U-ARF rats, the AUCSK3541/AUCmirodenafil ratios were comparable with that in controls and this could be due to further metabolism of SK3541 in rats.