Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0012833 (dizziness)
 9,689 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sildenafil citrate, an oral therapy for erectile dysfunction, is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), the predominant isozyme metabolizing cGMP in the corpus cavernosum. Chemically, it is a compound of the pyrazolo-pyrimidinyl-methylpiperazine class. Sildenafil has no direct relaxant effect on human corpus cavernosum but enhances the relaxant effect of nitric oxide (NO) on the corpus cavernosum by inhibiting PDE5, which is responsible for degradation of cGMP in this tissue. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil increases concentrations of cGMP in the corpus cavernosum, causing smooth muscle relaxation and blood flow into the penis, resulting in an erection. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. The drug is rapidly absorbed after oral administration, with absolute bioavailability of 40%. Its pharmacokinetics are dose proportional over the recommended dosage range. Maximum plasma concentrations are reached within 30 to 120 minutes after oral dosing in the fasting state. Sildenafil is cleared predominantly by the hepatic microsomal isoenzymes CYP3A4 (major route) and CYP2C9 (minor route). Clinical studies assessed the effect of sildenafil on the ability of men with erectile dysfunction to engage in sexual activity and, specifically, to achieve and maintain an erection sufficient for satisfactory sexual intercourse. Sildenafil was evaluated at doses of 25, 50, and 100 mg in randomized, double-masked, placebo-controlled clinical trials of up to 6 months' duration. The drug was administered to hundreds of patients aged 19 to 87 years having erectile dysfunction of various etiologies for a mean duration of 5 years. Sildenafil was associated with statistically significant improvement in erectile function compared with placebo. Adverse effects reported at a rate of >2% were headache, flushing, dyspepsia, nasal congestion, urinary tract infection, abnormal vision, diarrhea, dizziness, and rash. No cases of priapism were reported. The use of sildenafil is contraindicated in men who are taking organic nitrates, because of the potential for a precipitous decrease in blood pressure. Postmarketing reports and surveillance have revealed at least 39 deaths with sildenafil use in men having a history of heart disease, men taking nitrate medications, and men in poor physical health due to lack of exercise. Many of the men who experienced serious adverse effects or death had a variety of concomitant diseases and were taking multiple medications.
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PMID:Safety and efficacy of sildenafil citrate in the treatment of male erectile dysfunction. 991 1

The aim of this study was to assess the efficacy of sildenafil as the first-step tool for erectile dysfunction (ED) in Japanese males. Between March 1999 and March 2003, 281 patients were prescribed five tablets of sildenafil (50 mg) as the first step in the therapeutic management of ED. Of the 281 patients, 206 were evaluable patients. The overall success rate in achieving sexual intercourse in subjects after taking sildenafil was 77.2% (159/206), while 22.8% (47/206) were unsuccessful. The success rates in men with functional ED and organic ED were 91.4% (85/93) and 65.5% (74/113), respectively (P<0.0001). Overall, transient adverse effects of sildenafil occurred in 16 (8%) males. Intolerable adverse effects (edema and dizziness) occurred in only 1% of patients (2/206). Sildenafil citrate may be recommended as the first choice drug for ED because of its high success rate and low invasiveness.
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PMID:Efficacy of sildenafil as the first-step therapeutic tool for Japanese patients with erectile dysfunction. 1582 91

Sildenafil citrate (Viagra) is one of the frequently prescribed drugs for men with erectile dysfunction. We describe a 52-year-old man with bilateral middle cerebral artery (MCA) territory infarction after sildenafil use. He ingested 100 mg of sildenafil and about 1 h later, he complained of chest discomfort, palpitation and dizziness followed by mental obtundation, global aphasia and left hemiparesis. Brain magnetic resonance imaging documented acute bilateral hemispheric infarction, and cerebral angiography showed occluded bilateral MCA. Despite significant bilateral MCA stenosis and cerebral infarction, systemic hypotension persisted for a day. We presume that cerebral infarction was caused by cardioembolism with sildenafil use.
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PMID:Bilateral cerebral hemispheric infarction associated with sildenafil citrate (Viagra) use. 1829 Aug 52

Male erectile dysfunction is common and frustrating after the age of forty years. Erectile dysfunction is a cause of misery, relationship difficulties, and significantly reduced quality of life. Sildenafil citrate (Viagra) has shown promising results in recently published clinical trials. Sildenafil is a potent and competitive inhibitor of cGMp specific phosphodiesterase-5, predominant isoenzyme in the human corpus cavernosum. It is effective in erectile dysfunction of diverse origin, however it requires a patent vascular system to be effective. It is not effective in patients with endocrinal impotence, loss of libido, premature ejaculation or infertility. Its main adverse effects are headache, flushing, dyspepsia, diarrhoea, nasal congestion, indigestion, visual disturbances, dizziness and rash. Ventricular tachycardia and acute myocardial infraction have been reported in patients of ischaemic heart disease after consumption of sildenafil. Six deaths have been reported in patients taking nitrates. In India it is likely to be prescribed by a primary care physician without complete evaluation of patient on complaint of impotence. Hence the ethical question of who should prescribe this drug should be addressed by medical fraternity and proper guidelines formulated to avoid misuse of sildenafil. Phosphodiesterase is distributed in nerve, central nervous system, and systemic vasculature, hence long-term effects of drug on these tissues has to be ascertained. It should be made mandatory to report all adverse drug reactions to ADR monitoring centres. It is a wonder for those who require it, but has potentially dangerous adverse effects and drug interactions and hence is and not a wonder pill for all kinds of impotence.
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PMID:VIAGRA : IS IT A WONDER DRUG ? 2736 78