Sildenafil Tablets

Overview of Sildenafil Tablets

Dosage Strength

  • Commercial (Revatio®): 20 mg
  • Commercial (Viagra®): 100 mg
  • Commercial (Generic): 20 mg, 25 mg, 50 mg, 100 mg

General Information

Sildenafil is a vasoactive drug that is extensively used to treat erectile dysfunction (impotence) in males and to alleviate symptoms in pulmonary arterial hypertension patients (PAH). Sildenafil enhances blood flow to specific regions of the body, including the penis, by lowering vascular resistance and relaxing muscles. Sildenafil is usually given 30 to 60 minutes before sexual intercourse, although sildenafil troche can be taken up to 10 minutes before.

Sildenafil is the most widely used erectile dysfunction medication. Sildenafil was created by a team of pharmaceutical chemists at Pfizer’s Kent, England laboratory who collaborated to synthesize sildenafil. The drug was initially developed to treat hypertension (a sign of ischemic heart disease) and chest pains caused by insufficient blood circulation to the heart. In 1991 and 1992, the medication was tested on males at Morriston Hospital in Swansea. Its clinical trials were overseen by Ian Osterloh, who suggested that the medication had little effect on treating angina but had a considerable effect on penile erections. Pfizer opted to market the medication as an erectile dysfunction treatment.

Sildenafil belongs to the class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. Sildenafil was originally designed as an antianginal medication, but it was discovered to be more successful in the treatment of erectile dysfunction (ED). Sildenafil is still being examined therapeutically to determine its utility in treating female sexual dysfunction, although preliminary trials have found that it performs similarly to placebo in women. In 21 clinical trials, sildenafil was tried in almost 4000 men with ED. These guys were 55 years old on average, and they had ED for an average of 5 years before entering the study. Sildenafil was effective in around 70% of individuals. In trials of male patients with psychogenic ED, response rates of 90% were achieved. Sildenafil may also be beneficial in male individuals suffering from ED caused by diabetes mellitus1 or pelvic fracture urethral rupture. 2 Sildenafil has been demonstrated to be efficacious and well tolerated in patients on multimodal antihypertensive regimens, with no added safety hazards. 3 Oral phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are regarded first-line medication in ED treatment guidelines. 4 Sildenafil received final FDA approval for the treatment of ED in March 1998.

Studies conducted shortly after sildenafil was approved for ED revealed that it was useful in treating people with pulmonary arterial hypertension (PAH).

567 Sildenafil increased exercise capacity, mean pulmonary artery pressure, and other cardiac function measurements in PAH patients. Sildenafil is the first oral medicine licensed for the treatment of PAH in its early stages. Although preliminary data from 12 sickle cell anemia patients showed a reduction in PAH, a larger clinical trial (n = 134) investigating the use of sildenafil for pulmonary hypertension in adults with sickle cell anemia was halted early due to an increased risk of serious adverse effects, particularly sickle cell pain crises, when compared to placebo (38 percent vs. 8 percent , respectively). The cause of the increased risk of discomfort is unknown; nevertheless, patients in the earlier trial were aggressively treated with transfusions and hydroxyurea to control crises; the larger experiment did not offer any intervention for crises. Sildenafil has also been demonstrated to be effective in treating altitude sickness. 568 The FDA approved the oral formulation of sildenafil (Revatio) for the treatment of pulmonary arterial hypertension (PAH) in June 2005, and the injectable formulation in November 2009.


1.Basu A, Ryder REJ. New treatment options for erectile dysfunction in patients with diabetes mellitus. Drugs 2004;64:2667-88.
2.Shenfeld OZ, Gofrit ON, Gdor Y, et al. The role of sildenafil in the treatment of erectile dysfunction in patients with pelvic fracture urethral disruption. J Urol 2004;172:2350-2.
3.Pickering TG, Shepherd AM, Puddey I, et al. Sildenafil citrate for erectile dysfunction in men receiving multiple antihypertensive agents: A randomized controlled trial. Am J Hypertens 2004;17:1135-42.
4.Montague DK, Jarow JP, Broderick GA, et al. Chapter 1: The management of erectile dysfunction: an AUA update. J Urol 2005;174:230-9.
5.Abrams D, Schulze-Neick I, Magee AG. Sildenafil as a selective pulmonary vasodilator in childhood primary pulmonary hypertension. Heart 2000;84:E4.
6.Hossein AG, Wiedemann R, Rose F, et al. Combination therapy with oral sildenafil and inhaled iloprost for severe pulmonary hypertension. Ann Intern Med 2002;136:515-522.
7.Michelakis E, Tymchak W, Lien D, et al. Oral sildenafil is an effective and specific pulmonary vasodilator in patients with pulmonary arterial hypertension. Circulation 2002;105:2398-2403.
8.Richalet JP, Gratadour P, Robach P, et al. Sildenafil Inhibits the altitude-induced hypoxemia and pulmonary hypertension. Am J Respir Crit Care Med 2005;171(3):275-81. Epub 2004 Oct 29
9.Bortolotti M, Mari C, Giovannini M, et al. Effects of sildenafil on esophageal motility of normal subjects. Dig Dis Sci 2001;46:2301-2306.
10.Hansten PD, Horn JR. Cytochrome P450 Enzymes and Drug Interactions, Table of Cytochrome P450 Substrates, Inhibitors, Inducers and P-glycoprotein, with Footnotes. In: The Top 100 Drug Interactions – A guide to Patient Management. 2008 Edition. Freeland, WA
11.Viagra (sildenafil citrate) package insert. New York, NY: Pfizer; 2014 Mar.
12.Arruda-Olson AM, Mahoney DW, Nehra A, et al. Cardiovascular effects of sildenafil during exercise in men with known or probable coronary artery disease. JAMA 2002;287:719-725.
13.Borlaug BA, Melenovsky V, Marhin T, et al. Sildenafil inhibits β-adrenergic-stimulated cardiac contractility in humans. Circulation 2005;112:2642-49.
14.Burnett AL, Bivalacqua TJ. Priapism: current principles and practice. Urol Clin N Am 2007;34:631-642.
15.Levine LA, Latchamsetty KC. Treatment of erectile dysfunction in patients with Peyronie’s disease using sildenafil citrate. Int J Impot Res 2002;14:478-482.
16.Revatio (sildenafil citrate) package insert. New York, NY: Pfizer; 2014 Mar.
17.Food and Drug Administration (US FDA) News Release. FDA recommends against use of Revatio in children with pulmonary hypertension. Retrieved August 31, 2012. Available on the World Wide Web at:
18.Food and Drug Administration (US FDA) Drug Safety Communication. Revatio (sildenafil)-FDA clarifies warning about pediatric use for pulmonary arterial hypertension. Retrieved March 31, 2014. Available on the World Wide Web at:
19.Abman SH, Kinsella JP, Rosenzweig EB, et al. Implications of the U.S. Food and Drug Administration Warning against the use of sildenafil for the treatment of pediatric pulmonary hypertension. Am J Respir Crit Care Med 2013;187:572-5.
20.Hansten P, Horn J. The Top 100 Drug Interactions: A Guide to Patient Management. includes table of CYP450 and drug transporter substrates and modifiers (appendices). H & H Publications, LLP 2014 edition.
21.Viagra (sildenafil citrate) package insert. New York, NY: Pfizer; 2006 Oct.
22.Cialis (tadalafil) package insert. Indianapolis, IN: Lilly ICOS, LLC; 2011 Oct.
23.Levitra (vardenafil) package insert. Kenilworth, NJ: Schering-Plough; 2007 Mar.
24.Cialis (tadalafil) package insert. Indianapolis, IN: Lilly ICOS, LLC; 2007 Jan.
25.Intelence (etravirine) package insert. Titusville, NJ: Janssen Pharmaceuticals, Inc.; 2014 Aug.
26.Hall MCS, Ahmad S. Interaction between sildenafil and HIV-1 combination therapy. Lancet 1999;353;2071-2.
27.Norvir (ritonavir capsules) package insert. Chicago, IL: AbbVie Inc; 2013 Nov.
28.Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Department of Health and Human Services. Available at
29.Invirase (saquinavir) package insert. South San Francisco, CA: Genentech Inc.; 2012 Nov.
30.Lexiva (fosamprenavir calcium) package insert. Research Triangle Park, NC: ViiV Healthcare; 2013 Apr.
31.Agenerase (amprenavir) package insert. Research Triangle Park, NC: GlaxoSmithKline; 2005 Nov.
32.Reyataz (atazanavir) package insert. Princeton, NJ: Bristol-Myers Squibb Company; 2014 Jun.
33.Prezista (darunavir) package insert. Titusville, NJ: Janssen Pharmaceuticals, Inc.; 2014 Apr.
34.Tybost (cobicistat) package insert. Foster City, CA: Gilead Sciences, Inc; 2014 Sept.
35.Evotaz (atazanavir and cobicistat) tablet package insert. Princeton, NJ: Bristol-Myers Squibb Company; 2015 Jan.
36.Prezcobix (darunavir and cobicistat) tablets package insert. Titusville, NJ: Janssen Therapeutics; 2015 Jan.
37.Merry C, Barry MG, Ryan M, et al. Interaction of sildenafil and indinavir when co-administered to HIV-patients. AIDS 1999;13:F101-7.
38.Kaletra (lopinavir; ritonavir) tablet and solution package insert. North Chicago, IL: AbbVie Inc; 2015 Jan.
39.Viracept (nelfinavir mesylate) package insert. Research Triangle Park, NC: ViiV Healthcare Company; 2013 May.
40.Rescriptor (delavirdine) package insert. La Jolla, CA: Agouron Pharmaceuticals; 2006 Feb.
41.Sustiva (efavirenz) package insert. Princeton, NJ: Bristol-Myers Squibb Company; 2014 May.
42.Walters JS, Woodring JH, Stelling CB, Rosenbaum HD: Salicylate-induced pulmonary edema. Radiology 1983;146:289-293.
43.Hesse C, Siedler H, Burhenne J, et al. Fluvoxamine affects sildenafil kinetics and dynamics. J Clin Psychopharmacol 2005;25:589-92.
44.Balon R. Fluvoxamine-induced erectile dysfunction responding to sildenafil. J Sex Marital Ther 1998;24(4):313-7.
45.Emend capsules (aprepitant) package insert. Whitehouse Station, NJ: Merck & Co., Inc.; 2007 Nov.
46.Zithromax (azithromycin tablets and azithromycin oral suspension) package insert. New York, NY: Pfizer Inc.; 2004 Jan.
47.Biaxin (clarithromycin) package insert. North Chicago, IL: AbbVie, Inc.; 2015 Jan.
48.Vaprisol (conivaptan hydrochloride injection). Deerfield, IL: Astellas Pharma US, Inc.; 2007 Feb.
49.Cardizem LA (diltiazem) package insert. Mississauga, ON: Biovail Corporation; 2006 Apr.
50.Gleevec (imatinib mesylate) package insert. East Hanover, NJ: Novartis Pharmaceuticals Corporation; 2008 Dec.
51.Diflucan (fluconazole) package insert. New York, NY. Pfizer; 2004 Aug.
52.ProzacR (fluoxetine hydrochloride). Indianapolis, IN: Eli Lilly and Company; 2003 Nov.
53.Serzone (nefazodone) package insert. Princeton, NJ: Bristol-Myers Squibb Company; 2003 Sep.
54.Quinidex Extentabs (quinidine sulfate extended-release tablets) package insert. Richmond, VA: A.H. Robbins Company; 2000 Sept.
55.Ranexa (ranolazine extended-release tablets) package insert. Foster City, CA: Gilead Sciences, Inc. 2013 Dec.
56.Zagam (sparfloxacin) package insert. Research Triangle Park, NC: Bertek Pharmaceuticals; 2003 Feb.
57.Calan (verapamil tablets) package insert. Chicago, IL: GD Searle LLC; 2003 Jul.
58.VFEND (voriconazole) package insert. New York,NY: Pfizer Inc; 2008 Mar.
59.Accolate (zafirlukast) package insert. Wilmington, DE: AstraZeneca; 2004 Jul.
60.ZyfloT Filmtab (zileuton) package insert. Chicago, IL: Abbott Laboratories; 1998 Mar.
61.Tracleer (bosentan) package insert. South San Francisco, CA: Actelion Pharmaceuticals US, Inc.; 2007 Feb.
62.Tegretol (carbamazepine) package insert. East Hanover, NJ. Novartis Pharmaceuticals; 2003 Sept.
63.Phenytoin package insert. Morgantown, WV: Mylan Pharmaceuticals; 1998 Sep.
64.Cerebyx (fosphenytoin sodium) package insert. New York, NY: Parke-Davis; 2002 Jun.
65.Viramune (nevirapine) package insert. Ridgefield, CT: Boehringer Ingelheim Pharmaceuticals, Inc.; 2008 Jun.
66.Finch CK, Chrisman CR, Baciewicz AM, et al. Rifampin and rifabutin drug interactions: an update. Arch Intern Med 2002;162:985-92.
67.Mycobutin (rifabutin) package insert. Kalamazoo, MI:Pharmacia & Upjohn, Co.; 2001 Nov.
68.Rifampin Injection package insert. Bedford, OH: Bedford Laboratories; 2000 Nov.
69.Niemi M, Backman JT, Fromm MF, et al. Pharmacokinetic interactions with rifampicin [rifampin]. Clin Pharmacokinet 2003;42:819-50.
70.Rezulin (troglitazone) package insert. Morris Plains, NJ: Parke-Davis; 1999 June. NOTE: Troglitazone was removed from the US market in response to FDA concerns in March 2000.
71.Propulsid (cisapride) package insert. Titusville, NJ; Janssen Pharmaceutica; 2000 Jan. NOTE: As of May 2000; Propulsid has only been available in the United States via an investigational limited access program to ensure proper patient screening and pres
72.Michalets EL, Williams CR. Drug interactions with cisapride: clinical implications. Clin Pharmacokinet 2000;39:49-75.
73.Mifeprex (mifepristone, RU-486) package insert. New York, NY: Danco Laboratories, LLC; 2009 Apr.
74.Korlym (mifepristone) tablet package insert. Menlo Park, CA: Corcept Therapeutics Incorporated; 2013 Jun.
75.Christ B, Brockmeier D, Hauck EW, et al. Interactions of sildenafil and tacrolimus in men with erectile dysfunction after kidney transplantation. Urology. 2001 Oct;58(4):589-93.
76.De Rose AF, Giglio M, Traverso P, et al. Combined oral therapy with sildenafil and doxazosin for the treatment of non-organic erectile dysfunction refractory to sildenafil monotherapy. Int J Impot Res 2002;14:50-3.
77.Jetter A, Kinzig-Schippers M, Walchner-Bonjean M, et al. Effects of grapefruit juice on the pharmacokinetics of sildenafil. Clin Pharmacol Ther 2002;71:21-9.
78.Goldmeier D. Prolonged erections produced by dihydrocodeine and sildenafil. Br Med J 2002;324:1555. Letter.
79.NardilR (phenelzine) package insert. New York, NY: Pfizer; 2003.
80.ParnateR (tranylcypromine) package insert. Research Triangle Park, NC: GlaxoSmithKline; 2001 Aug.
81.Casper F, Petri E. Local treatment of urogenital atrophy with an estrodiol-releasing vaginal ring: a comparative and a placebo-controlled multicenter study. Vaginal Ring Study Group. Int Urogynecol J Pelvic Floor Dysfunct 1999;10:171-6
82.Adalat CC (nifedipine extended-release tablets) package insert. West Haven, CT: Bayer Pharmaceuticals Corporation; 2010 Aug.
83.Stribild (elvitegravir; cobicistat; emtricitabine; tenofovir) package insert. Foster City, CA: Gilead Sciences, Inc; 2014 Dec.
84.Milman HA, Arnold SB. Neurologic, psychological, and aggressive disturbances with sildenafil. Ann Pharmacother 2002;36:1129-1134.
85.Gilad R, Lampl Y, Eshel Y, Sadeh M. Tonic-clonic seizures in patients taking sildenafil. BMJ 2002;325-869.
86.Pomeranz HD, Bhavsar AR. Nonarteritic ischemic optic neuropathy developing soon after use of sildenafil: a report of seven new cases. J Neuroophthalmol 2005;25:9-13.
87.Escaravage GK Jr, Wright JD Jr, Givre SJ. Tadalafil associated with anterior ischemic optic neuropathy. Arch Ophthalmol 2005;123(3):399-400.
88.Bollinger K, Lee MS. Recurrent visual field defect and ischemic optic neuropathy associated with tadalafil rechallenge. Arch Ophthalmol 2005;123(3):400-1.
89.Peter NM, Singh MV, Fox PD. Tadalafil-associated anterior ischaemic optic neuropathy. Eye 2005;19(6):715-7.

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