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Sildenafil Half Life

Sildenafil Half Life


viagra is an oral medication affectionately called the “little blue pill” and is taken 30-60 minutes before anticipated sexual arousal. it “lasts” for up to four hours. this means that enough of the medication is still circulating in your blood stream in the event that you become sexually aroused. since this is a common question, we have delved deeper into this issue. according to the viagra package insert by pfizer, the half-life of viagra is four hours. that means that four hours after ingesting the little blue pill the concentration of viagra in your blood stream is one half of what it was shortly after swallowing it. after that point, the effectiveness of the product begins to lessen substantially. from this information, we derive that once half of the medication has been dismantled by the liver that it ceases to have less of an effect during sexual arousal. typically, a medication is not considered “completely” out of the system until five half-lives have passed. in this case, it is 20 hours after ingestion that viagra is completely “out of the system,” but it becomes less effective after only four hours. please take only as prescribed. at the recommended doses there is no effect on an erection unless the patient becomes sexually aroused. at higher doses, it can become more toxic and the side effects more pronounced.


sildenafil is an oral therapy for erectile dysfunction which restores impaired erectile function by increasing blood flow to the penis, resulting in a natural response to sexual stimulation. the physiological mechanism responsible for erection of the penis involves the release of nitric oxide (no) in the corpus cavernosum during sexual stimulation. nitric oxide then activates the enzyme, guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cgmp), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.

clinical trials

the efficacy and safety of sildenafil was evaluated in 21 randomised, double-blind placebo controlled trials of up to 6 months duration. sildenafil was administered to more than 3,000 patients aged 19-87, with erectile dysfunction (ed) of various aetiologies (organic, psychogenic, mixed). the efficacy was evaluated by global assessment question, diary of erections, the international index of erectile function (iief, a validated sexual function questionnaire) and a partner questionnaire. sildenafil efficacy, determined as the ability to achieve and maintain an erection sufficient for sexual intercourse, was demonstrated in all 21 studies and was maintained in long term extension studies (one year). in fixed dose studies the proportions of patients reporting that treatment improved their erections were 62% (25 mg), 74% (50 mg) and 82% (100 mg), compared to 25% on placebo. in addition to improvements in erectile function, analysis of iief showed that sildenafil treatment also improved the domains of orgasm, satisfaction with intercourse and overall satisfaction.


use of sildenafil is contraindicated in patients with known hypersensitivity to any component of the tablet. sildenafil was shown to potentiate the hypotensive effects of acute and chronic nitrates, and its co-administration with nitric oxide donors, organic nitrates or organic nitrites in any form, either regularly or intermittently, is therefore contraindicated. drugs which must not be used concomitantly include glyceryl trinitrate (injection, tablets, sprays or patches), isosorbide salts, sodium nitroprusside, amyl nitrite, nicorandil or organic nitrates in any form. (see warnings and precautions).