Bioequivalence study of sildenafil citrate tablets in healthy human volunteers

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Evaluation of a progressive treatment program for erectile dysfunction in patients with diabetes mellitus.

Israilov S, Shmuely J, Niv E, Engelstein D, Livne P, Boniel J.

1Institute of Urology, Rabin Medical Center, Beilinson Campus, Petah Tiqwa, Israel.

The aim was to evaluate the effectiveness of a progressive program, starting with simple methods and, when not effective, moving to more complex methods, to treat erectile dysfunction (ED) in patients with diabetes mellitus. A total of 284 diabetic patients with ED entered into a 6-phase program starting with sildenafil citrate (Viagra). Those with contraindications, side effects, or negative response (erection insufficient for vaginal penetration) were switched to the vacuum erection device (VED), and then progressively (for failures) to intracavernous injection (ICI), sildenafil citrate+ICI, ICI+VED, and penile prosthesis. Patients were followed for 2 y. Of the 284 patients 276 patients were eligible for sildenafil citrate and 147 (53.3%) responded positively, but 25 (9.1%) patients stopped it soon due to adverse effects. Of 162 patients (129 nonresponders, eight noneligible for the sildenafil and 25 patients who dropped out due to adverse effects), treated with VED, 114 (70.4%) responded well, however, only 19 (11.7%) patients agreed to continue its use. Of the remaining 143 patients (nonresponders, noneligible for the previously mentioned treatments and patients who dropped out due to adverse effects), 103/143 (72%) responded to ICI, 27/40 (67.5%) to sildenafil+ICI, and 9/13 (69.2%) to ICI+VED. Four patients received a penile implant. At the 2 y follow-up, 81 of 284 patients who entered the study (28.5%) were still responding to sildenafil, seven (2.5%) to VED, 113 (39.8%) to ICI, 24 (8.5%) to sildenafil+ICI, two (0.7%) to ICI+VED; 15 (5.3%) had a penile implant. In all 17 (6%) patients reported spontaneous erections, 11 (3.9%) stopped the treatment due to family reasons and 14 (4.9%) failed the treatment. In conclusion, the progressive treatment program for ED seems to be very effective for diabetic patients, yielded a complete response for short-term and 91.2% rate of success at the end of 2 y follow-up.International Journal of Impotence Research advance online publication, 12 May 2005; doi:10.1038/sj.ijir.3901337.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15889124&query_hl=1

Hemodynamic effects of sildenafil in patients with congestive heart failure and pulmonary hypertension: combined administration with inhaled nitric oxide.

Lepore JJ, Maroo A, Bigatello LM, Dec GW, Zapol WM, Bloch KD, Semigran MJ.

Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.

STUDY OBJECTIVES: In patients with pulmonary hypertension (PH) secondary to congestive heart failure, inhaled nitric oxide (NO) increases pulmonary vascular smooth-muscle intracellular cyclic guanosine monophosphate (cGMP) concentration, thereby decreasing pulmonary vascular resistance (PVR) and increasing cardiac index (CI). However, these beneficial effects of inhaled NO are limited in magnitude and duration, at least in part due to cGMP hydrolysis by the type 5 isoform of phosphodiesterase (PDE5). The goal of this study was to determine the acute pulmonary and systemic hemodynamic effects of the selective PDE5 inhibitor, sildenafil, administered alone or in combination with inhaled NO in patients with congestive heart failure and PH. DESIGN: Single center, case series, pharmacohemodynamic study. SETTING: Cardiac catheterization laboratory of a tertiary care academic teaching hospital. PATIENTS: We studied 11 patients with left ventricular systolic dysfunction due to coronary artery disease or idiopathic dilated cardiomyopathy who had PH. INTERVENTIONS: We administered oral sildenafil (50 mg), inhaled NO (80 ppm), and the combination of sildenafil and inhaled NO during right-heart and micromanometer left-heart catheterization. MEASUREMENTS AND RESULTS: Sildenafil administered alone decreased mean pulmonary artery pressure by 12 +/- 5%, PVR by 12 +/- 5%, systemic vascular resistance (SVR) by 13 +/- 6%, and pulmonary capillary wedge pressure by 12 +/- 7%, and increased CI by 14 +/- 5% (all p < 0.05) [+/- SEM]. The combination of inhaled NO and sildenafil decreased PVR by 50 +/- 4%, decreased SVR by 24 +/- 3%, and increased CI by 30 +/- 4% (all p < 0.01). These effects were greater than those observed with either agent alone (p < 0.05). In addition, sildenafil prolonged the pulmonary vasodilator effect of inhaled NO. Administration of sildenafil alone or in combination with inhaled NO did not change systemic arterial pressure or indexes of myocardial systolic or diastolic function. CONCLUSIONS: PDE5 inhibition with sildenafil improves cardiac output by balanced pulmonary and systemic vasodilation, and augments and prolongs the hemodynamic effects of inhaled NO in patients with chronic congestive heart failure and PH.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15888841&query_hl=1

Effect of sildenafil on reperfusion function, infarct size, and cyclic nucleotide levels in the isolated rat heart model.

du Toit EF, Rossouw E, Salie R, Opie LH, Lochner A.

Department of Medical Physiology, Faculty of Health Science, University of Stellenbosch, Tygerberg, South Africa.

We have previously shown that NO-donor induced elevation in myocardial cGMP levels is associated with improved reperfusion function of the isolated rat heart. The phosphodiesterase 5 (PDE 5) inhibitor, sildenafil could potentially increase myocardial cGMP levels and thus protect the heart against ischaemic/reperfusion injury.Methods: To test our hypothesis we treated the isolated working rat heart with vehicle, OR sildenafil (10, 20, 50, 100, 200 nM), OR sildenafil (50 nM) plus a sarcolemmal (HMR 1098) or a mitochondrial (5-Hydroxydecanoate (5-HD)) K(ATP) channel blocker. Hearts were then subjected to 20 min global, or 35 min regional ischaemia at 37( composite function)C before reperfusion function (aortic output, coronary flow and aortic pressure) and infarct size were documented. Pre-ischaemic, ischaemic and reperfusion myocardial cAMP and cGMP concentrations were determined.Results: Low concentrations of sildenafil (10, 20 and 50 nM) improved reperfusion aortic output (AO) recovery (61.4+/- 4.5%, 64.8 +/- 5.2% and 62.3 +/- 5.0% vs. 45.4 +/- 3.8% for controls (p < 0.05)) and infarct size, while high concentrations (200 nM) worsened AO recovery (24.9 +/- 4.9.0%, p < 0.05). Myocardial cGMP levels of ischaemic tissue were elevated (34.7 +/- 2.4 vs. 27.3 +/- 2.2 pmol/g ww) and cAMP levels were suppressed (0.59 +/- 0.03 vs. 0.87 +/- 0.06 nmol/g ww) in the sildenafil (50 nM) treated hearts. Co-perfusion with sildenafil plus HMR 1098 decreased AO recovery (21.7 +/- 7.6% vs. 62.3 +/- 5.0% for sildenafil alone, p < 0.05) and increased infarct size (29.7 +/- 2.04% vs. 8.6 +/- 2.39% for sildenafil alone, p < 0.05).Similarly, sildenafil plus 5-HD decreased reperfusion AO recovery (44.4 +/- 6.0% vs. 62.3 +/- 5.0% for sildenafil alone, p < 0.05) and increased infarct size (33.8 +/- 1.62% vs. 8.6 +/- 2.39% for sildenafil alone, p < 0.05).Conclusions: (1) Pretreatment with low concentrations of sildenafil (20-50 nM) improves, while higher concentrations (200 nM) worsen reperfusion function in this model. (2) Low concentrations of sildenafil (20-50 nM) decrease infarct size while the higher concentrations had no effect. (3) These protective properties of low concentrations of sildenafil may be related to its cGMP elevating and cAMP suppressing effects in the ischaemic heart. (4) Possible end-effectors for sildenafil in the ischaemic heart include the mitochondrial and sarcolemmal K(ATP) channel.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15883753&query_hl=1

Bioequivalence study of sildenafil citrate tablets in healthy human volunteers.

Mandal U, Musmade P, Chakraborty M, Rajan DS, Chakravarti M, Pal TK, Chattaraj TK.

Bioequivalence Study Centre, Department of Pharmaceutical Technology, Jadavpur University, Kolkata India.

Newly developed sildenafil citrate (SC), a selective inhibitor of cyclic guanosine monophosphate (c-GMP) specific phosphodiesterase type 5 (PDE 5) in the corpus cavernosum is used for the oral treatment of erectile dysfunction. A convenient, sensitive and simple method for the determination of sildenafil in human plasma is presented. The analytical technique was based on reversed-phase high-performance liquid chromatography coupled with UV detector set at 295 nm. Rofecoxib was used as internal standard (I.S). Liquid-liquid extraction using diethyl ether was performed to recover sildenafil and rofecoxib. The retention time of I.S and sildenafil were 5.5 minutes and 7.2 minutes respectively. The method was validated over a linear range of 10 to 1000 ng/ml from plasma. Separate stability study showed that sildenafil is stable under conditions of analysis. The extraction efficiency from plasma varied from 79.69% to 81.13 %. The minimum quantifiable concentration was set at 10 ng/ml. (%o CV<12.5%). The method was used for Bioequivalence Study of Two Brands of Sildenafil citrate 50 mg tablets in healthy human volunteers. All pharmacokinetic parameter were calculated along with statistical evaluation.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15881813&query_hl=1

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