VIAGRA [Sildenafil citrate] An Overview
Coming back to VIAGRA [Sildenafil citrate], Viagra is a selective and potent inhibitor of cyclic guanosine monophosphate [cGMP] specific phosphodiesterase type 5 inhibitor [PDE5] which is the predominant phosphodiesterase isoform found in the penis. It is administered in doses of 25, 50 and 100 mg, and enhances erection after sexual stimulation. The onset of action is around 60-90 mins. Sildenafil (compound UK-92,480) was synthesised by a group of chemists working at Pfizer's Sandwich, Kent research facility in England. It was initially studied for use in hypertension and angina pectoris. The first clinical trials were conducted at Morriston Hospital in Swansea. Phase, I clinical trials under the direction of Ian Osterloh, suggested that the drug had little effect on angina, but that it could induce marked penile erections. VIAGRA [Sildenafil citrate] was approved for use in erectile dysfunction by the Food and Drug Administration on March 27, 1998.
It's becoming the first pill approved to treat erectile dysfunction Reduced initial doses should be considered for patients, who are elderly, have renal insufficiency, or are taking medications that inhibit the CYP3A4 metabolic pathway in the liver [e.g., erythromycin, cimetidine, ketoconazole] as they may increase the serum concentration of sildenafil. The drug does not affect ejaculation, orgasm or sexual drive. When sexual stimulation causes local release of NO, inhibition of PDE5 by VIAGRA [Sildenafil citrate] causes increased levels of cGMP in the corpus cavernosum of the penis resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum.
Side Effects: - Headaches - Facial flushing - ringing in ears, or sudden hearing loss - Dyspepsia - Nasal congestion. - Abnormal vision [blue halo effect] - Diarrhea - Dizziness - Rashes - Viagra can decrease blood flow to the optic nerve of the eye, causing sudden vision loss - Special precautions: In patients with - Bleeding disorders such as hemophilia - Liver disorder - Kidney disorder - Active peptic ulcerations and - Anatomical deformation of the penis, such as Peyronie's disease. - Retinitis pigmentosa Contraindications: VIAGRA [Sildenafil citrate], is contraindicated in men receiving nitrate therapy for cardiovascular disease, including agents delivered by oral, sublingual, trans-nasal or topical routes. These agents can potentates its hypotensive effect and may result in profound shock. Viagra should be avoided in patients with congestive heart failure and cardiomyopathy because of the risk of vascular collapse.
There are other brands: - Caverta: Ranbaxy - Alisgra: Alembic - Euthanasia: Lupin Remedies - Juan: Cadillac - Silagra: Cipla - Jamie is the author of Viagra, Sildenafil Citrate information located at Genericsmed.com site References: - Harrison’s Principles of Internal Medicine, 15th Edition, pg 294 - Drug Today, July-September 2005 Edition, pg 522 - Pharmacology and Pharmacotherapeutics, R.S.Satoskar, S.D.Bhandarkar, S.S.Ainapure, Revised 17th Edition, pg 979 - http://www.drugs.com/viagra.html - http://www.rxlist.com/cgi/generic/viagra.htm - http://en.wikipedia.org/wiki/Viagra