BACKGROUND This study investigated the effect of the phosphodiesterase 5 inhibitor sildenafil on the pulmonary vascular response to hypoxia in humans and mice. METHODS AND RESULTS In a randomized, double-blind study, sildenafil 100 mg or placebo was given orally to 10 healthy volunteers 1 hour before breathing 11% O(2) for 30 minutes. Pulmonary artery pressure (PAP) was measured with an indwe...

BACKGROUND It has not previously been reported that sildenafil citrate causes malignant arrhythmias in humans. CASE PRESENTATION A 41-year-old man developed sustained ventricular tachycardia following sildenafil citrate administration. CONCLUSION It cannot be dismissed that this patient experienced ventricular tachycardia as an adverse effect of sildenafil citrate administration.

Sildenafil slows down the gastric emptying of a liquid test meal in awake rats and inhibits the contractility of intestinal tissue strips. We studied the acute effects of sildenafil on in vivo intestinal transit in rats. Fasted, male albino rats (180-220 g, N = 44) were treated (0.2 mL, iv) with sildenafil (4 mg/kg) or vehicle (0.01 N HCl). Ten minutes later they were fed a liquid test meal (99...

In some patients, heart failure (HF) is associated with increased pulmonary vascular resistance (PVR). The magnitude and the reversibility of PVR elevation affect the HF management. Sildenafil has been recently recognized as potent PVR-lowering drug in HF. The aim of the study was to compare hemodynamic effects and pulmonary selectivity of sildenafil to prostaglandin E(1) (PGE(1)). Right-heart ...

Epidemiological research indicates that sildenafil (Viagra) abuse is associated with increased risk behaviors. The present study employs the open field, a standard animal model used in the field of anxiety research, to examine whether chronic exposure to sildenafil affects anxiety and risk-taking behaviors in gonadally intact and castrated male Wistar rats. Sildenafil (10 mg/kg) or saline were ...

OBJECTIVE In this pilot study, the effect of sildenafil on digital ulcer (DU) healing and related clinical symptoms was analysed. METHODS A total of 19 patients with systemic sclerosis (SSc) were treated with maximally tolerated sildenafil doses up to 6 months. Primary outcome was the healing of DUs. Changes in other clinical symptoms were also evaluated. RESULTS In all, 49 DUs were present...

Endothelial dysfunction caused by defective nitric oxide (NO) signaling plays a pivotal role in the pathogenesis of intermittent claudication (IC). In the present study, we evaluated the acute effects of sildenafil, a phosphodiesterase type 5 inhibitor that acts by prolonging NO-mediated cGMP signaling in vascular smooth muscle, on blood pressure (BP), skeletal muscle oxygenation, and walking t...

The cGMP-binding cGMP-specific phosphodiesterase (PDE5) degrades cGMP and regulates the intracellular level of cGMP in many tissues, including the smooth muscle of the corpus cavernosum of the penis. Sildenafil (Viagra), a specific PDE5 inhibitor, promotes penile erection by blocking the activity of PDE5, which causes cGMP to accumulate in the corpus cavernosum. In the present study, sildenafil...

We studied the effects of sildenafil, a selective inhibitor of PDE5, on the development and the expression of tolerance to diazepam (DZ)-induced motor impairment and sedation in mice. DZ-induced motor incoordination was assessed by the rotarod and chimney tests, and DZ-induced sedation was examined using a photocell apparatus. Sildenafil treatment enhanced the development of tolerance to the mo...

Background: Experimental studies have shown that sildenafil may have significant cardio protective effects if used in low doses. The aim of this study was to compare the efficacies of glucagon and sildenafil treatments in anesthetized rats receiving verapamil overdose. Methods: Male Sprague-Dawley rats (n = 8 per group), weighing 300-350 g were used in the study. The iliac arteries and veins of...