Sildenafil / Tadalafil Capsule

Overview of Sildenafil / Tadalafil Capsule

Dosage Strength

55/12.5 mg

General Information

Sildenafil
Originally intended to treat pulmonary hypertension, angina, and other cardiovascular diseases, sildenafil citrate was unintentionally discovered to be useful in males suffering from erectile dysfunction (ED). Prior to the discovery of its therapeutic effects in the treatment of ED, this condition was thought to be an unavoidable component of aging in men or the result of underlying psychological problems. After being approved by the U.S. Food and Drug Administration in 1998 for the treatment of ED, sildenafil citrate’s popularity has skyrocketed over the last few decades, with health care providers generally recommending this medication as first-line therapy in the management of erectile dysfunction in men. Other aspects that contribute to its attraction and popularity include the fact that sildenafil citrate can be taken orally on demand and is generally well tolerated with little side effects. 1

Sildenafil citrate is a vasoactive medicine that belongs to the pharmacologic class of PDE-5 inhibitors; it is a competitive antagonist of this enzyme. PDE-5 is distributed throughout the human body, particularly in the corpus cavernosum within the penis, striated and smooth muscle, and platelets. However, PDE-5 is more prevalent in the penile corpus cavernosum, which explains why sildenafil citrate can function selectively in this area of the body. 2

Sildenafil citrate is often used orally. It can, however, be given intravenously or sublingually. Although its most common therapeutic application is for the treatment of erectile dysfunction, it is also used to treat pulmonary hypertension, infant pulmonary hypertension, Raynaud’s phenomenon refractory to other vasodilators, and to prevent pulmonary edema at high altitudes. Following oral administration, sildenafil citrate is rapidly absorbed, primarily in the small intestine, and is then carried through the bloodstream to its site of action. The hepatic isoenzymes cytochrome P450 3A4 and cytochrome P450 2C9 metabolize sildenafil citrate in the liver. Following hepatic metabolism, metabolites are primarily eliminated in the stool and, to a lesser extent, in the urine. 234

The Food and Medication Administration classifies sildenafil citrate as a pregnancy category B drug. Studies have found no definitive dangers to fetuses when sildenafil is given to pregnant women. There are currently no proven clinical indications for the use of sildenafil citrate in women. To yet, no studies have shown that sildenafil citrate has the same benefits in women as it does in men. Other trials, however, are still continuing, and the results may provide additional insight into the usability and benefits of sildenafil in women. 56

Tadalafil
Tadalafil, like sildenafil and vardenafil, is a selective phosphodiesterase (PDE) type 5 inhibitor. It is used orally and is used to treat male erectile dysfunction (ED), pulmonary arterial hypertension (PAH), benign prostatic hypertrophy (BPH), or both erectile dysfunction and BPH. Tadalafil does not suppress prostaglandins like certain impotence medications (e.g., alprostadil). Visual problems have not been recorded with tadalafil, which is more selective for PDE5 than PDE6 in the retina, unlike sildenafil. Tadalafil appears to have a longer duration of action (up to 36 hours) than sildenafil and vardenafil for the treatment of ED. Because PDE inhibitors only enhance erections in the presence of sexual stimulation, tadalafil’s longer duration of action allows for greater spontaneity in sexual engagement. Oral phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are regarded first-line medication in ED treatment guidelines. 7 Tadalafil was in phase II studies for the treatment of female sexual dysfunction, but further research was halted. In November 2003, the FDA approved it for the treatment of male erectile dysfunction (ED), then in January 2008, it was approved for once-daily usage without respect to sexual activity timing. Tadalafil (Adcirca) was approved by the FDA in May 2009 for the treatment of pulmonary arterial hypertension (PAH). Tadalafil-treated participants in clinical studies with pulmonary arterial hypertension (PAH) had greater exercise capacity and less clinical deterioration compared to placebo. Tadalafil was approved by the FDA in October 2011 for the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH) as well as the combined treatment of erectile dysfunction and BPH.

References

1.Goldstein, I., Burnett, A., Rosen, R.C., Park, P.W., Stecher, V.J.,” The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction”, Sexual Medicine Reviews, vol.7 issue 1, pp. 115-128. 2019. Available: https://www.sciencedirect.com/science/article/pii/S2050052118300830?via%3Dihub
2.McCullough, A.R., “Four-Year Review of Sildenafil Citrate”, Reviews in Urology, vol.4 supp 3, S26 – S38. 2002. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476025/
3.”Sildenafil citrate”, Prescribers Digital Reference. Available: https://www.pdr.net/drug-summary/Viagra-sildenafil-citrate-471
4.”Sildenafil”, Drug Bank. Available: https://go.drugbank.com/drugs/DB00203
5.Dastjerdi, M.V., Hosseini, S., Bayani, L., “Sildenafil citrate and uteroplacental perfusion in fetal growth restriction”, Journal of Research in Medical Sciences, vol.17 issue 7, pp.632-636. 2012. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3685778/
6.Monte, G.L., Graziano, A., Piva, I., Marci, R., “Women taking the “blue pill” (sildenafil citrate): such a big deal?”, Drug Design, Development, and Therapy. Vol.8, pp. 2251-2254. 2014. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232035/
7.Montague DK, Jarow JP, Broderick GA, et al. Chapter 1: The management of erectile dysfunction: an AUA update. J Urol 2005;174:230-9.
8.Cialis (tadalafil) package insert. Indianapolis, IN: Lilly ICOS, LLC; 2011 Oct.
9.Adcirca (tadalafil) package insert. Indianapolis, IN: Lilly ICOS, LLC; 2011 Apr.
12.Smith, B.P., Babos, M., “Sildenafil”, StatPearls. 2020. Available: https://www.ncbi.nlm.nih.gov/books/NBK558978/
13.Burnett AL, Bivalacqua TJ. Priapism: current principles and practice. Urol Clin N Am 2007;34:631-642.
14.Bortolotti M, Mari C, Giovannini M, et al. Effects of sildenafil on esophageal motility of normal subjects. Dig Dis Sci 2001;46:2301-2306.
15.Padma-Nathan H, McMurray JG, Pullman WE, et al. On-demand IC351 (Tadalafil) enhances erectile function in patients with erectile dysfunction. Int J Impot Res 2001;13:2-9.
16.Pomeranz HD, Bhavsar AR. Nonarteritic ischemic optic neuropathy developing soon after use of sildenafil (Viagra): a report of seven new cases. J Neuroophthalmol 2005;25:9-13.
17.Escaravage GK Jr, Wright JD Jr, Givre SJ. Tadalafil associated with anterior ischemic optic neuropathy. Arch Ophthalmol 2005;123(3):399-400.
18.Bollinger K, Lee MS. Recurrent visual field defect and ischemic optic neuropathy associated with tadalafil rechallenge. Arch Ophthalmol 2005;123(3):400-1.
19.Peter NM, Singh MV, Fox PD. Tadalafil-associated anterior ischaemic optic neuropathy. Eye 2005;19(6):715-7.

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