Inhibition by sildenafil of contractility of isolated non-pregnant human myometrium

A Comparison of Nifedipine Versus a Combination of Nifedipine and Sildenafil Citrate in the Management of Preterm Labour

Background Preterm delivery is a significant contributor to neonatal and infant morbidity and mortality. Preventive methods are preferable to treatment protocols for reducing perinatal mortality and morbidity. The calcium channel blocker nifedipine has the potential to be employed as a tocolytic, whereas the phosphodiesterase inhibitor sildenafil citrate promotes smooth muscle relaxation. Objective This study aims to examine the tocolytic effect of nifedipine in combination with sildenafil citrate in managing preterm labour (PTL). Methods After approval from the ethical board, 160 patients fulfilling the selection criteria were enrolled in the study from the outpatient and emergency department of obstetrics and gynaecology, University of Lahore, Pakistan. After taking written informed consent, their demographic profile, i.e., name, age, gestational age at presentation, parity, and expected date of delivery was noted. Patients were randomly assigned in a 1:1 ratio to two study groups (Group A: sildenafil citrate + nifedipine) and (Group B: nifedipine) using a computer-generated random number table to obtain a trial sequence. In group A, each patient was given nifedipine 20 mg orally, followed by 10 mg orally every eight hours for 48 hours and vaginal administration of sildenafil citrate, 25 mg at eight-hour intervals, for 48 hours. In group B, females were given nifedipine 20 mg orally, followed by 10 mg orally every 8 hours for 48 hours. They were kept admitted for 72 hours. SPSS Statistics version 21.0 (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.) was used to enter and analyse the collected data. Mean and standard deviation was calculated for quantitative variables like age, gestational age at presentation, gestational age at delivery, and BMI. Frequency and percentage were calculated for parity and preterm delivery. Results The study involved 160 patients, with the average age in Group A being 29.60±4.9 years and in Group B being 30.96±4.98 years. In terms of gestational age at delivery, Group A had an average of 34.16±1.7 weeks, while Group B had an average of 33.5±1.8 weeks (p-value<0.05). Preterm delivery was observed in 68.5% of Group A and 41.3% of Group B, with a significant p-value of 0.001. The study also discovered that the duration of prolonged pregnancy was significantly higher in Group A compared to Group B, with averages of 14.96±10.37 days and 10.24±8.97 days, respectively (p-value=0.002). Conclusion The results of this study suggest that the combination of sildenafil citrate and nifedipine may offer a promising new approach to improving pregnancy outcomes in cases of PTL. In the present study, sildenafil citrate plus nifedipine showed a significant effect in the management of PTL and prolongation in mean gestational age at delivery.

Avanafil Inhibits the Contractility of the Isolated Caprine Detrusor Muscle

Context:

Avanafil is a smooth muscle relaxant that is clinically used to treat erectile dysfunction. It is an inhibitor of phosphodiesterase-5 (PDE5), the enzyme that catalyzes the metabolism of cyclic guanosine monophosphate (cGMP). The inhibitory effect of avanafil on isolated detrusor muscle contractility has not been studied.

Aims:

This study investigated the inhibitory effect of avanafil on isolated caprine (goat) detrusor muscle contractility and the possible mechanisms involved.

Settings and Design:

80 mM potassium chloride (KCl)-induced contractility of the isolated goat detrusor was studied using a physiograph.

Materials and Methods:

Ten caprine detrusor strips were made to contract using 80 mM KCl before and after addition of three concentrations (10, 30, and 60 μM) of avanafil. Three reversal agents, ODQ, a guanylyl cyclase inhibitor; glibenclamide, an adenosine triphosphate (ATP)-sensitive potassium channel blocker; and iberiotoxin, a calcium-sensitive potassium (BKCa) channel blocker, were investigated for their ability to reverse the inhibitory effect of 30 μM avanafil on KCl-induced detrusor contractility.

Statistical Analysis Used:

The nonparametric statistical test, Kruskal–Wallis test, was used for the analysis of the data.

Results:

Avanafil caused a statistically significant inhibition of detrusor contractility at 30 and 60 μM concentrations. The inhibitory effect of 30 μM avanafil on detrusor contractility was significantly reversed by the addition of ODQ, glibenclamide, and iberiotoxin.

Conclusions:

Avanafil inhibits the contractility of the isolated detrusor by inhibiting PDE5, leading to raised cellular levels of cGMP. The raised levels of cGMP could have inhibited detrusor contractility by activating cGMP-dependent protein kinase, by opening ATP-sensitive potassium channels, and by opening BKCa. Avanafil could be evaluated for treating clinical conditions requiring relaxation of the detrusor like overactive bladder.

Inhibition by tadalafil of contractility of isolated nonpregnant human myometrium

Objective:

To investigate the inhibitory effect of tadalafil on the contractility of isolated nonpregnant human myometrium.

Materials and Methods:

The ability of tadalafil (25, 40, and 63 μM) to inhibit 55 mM KCl-induced contractility of isolated nonpregnant human myometrium was studied. The ability of the ATP-sensitive potassium channel blocker glibenclamide (10 μM) and the calcium-sensitive potassium channel (BKCa) blocker iberiotoxin (100 nM) to reverse the inhibitory effect of 40 μM tadalafil on 55 mM KCl-induced myometrial contractility was also studied.

Results:

Tadalafil produced a concentration-dependent inhibition of myometrial contractility that was statistically significant at 40 and 63 μM concentrations of tadalafil. The inhibition by tadalafil of myometrial contractility was statistically significantly reversed by the concurrent administration of glibenclamide and iberiotoxin.

Conclusions:

These results suggest that tadalafil inhibits human myometrial contractility by opening ATP-sensitive potassium channels and BKCa channels. The opening of these channels could have been due to the action of raised intracellular levels of cGMP due to inhibition of PDE-5 by tadalafil. The results suggest that tadalafil could be investigated for use in clinical conditions requiring relaxation of the myometrium.