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- Phosphodiesterase type-5 Inhibitor
- Sildenafil Citrate
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- Under FDA Review
Sildenafil Citrate (Revatio®,Viagra®)
Sildenafil Citrate, marketed under the trade names Viagra® and Revatio®, is a powerful vasodilator. It works by relaxing smooth muscle in blood vessels throughout the body which results in an increase in blood flow. Pfizer initially targeted the drug to treat male erectile dysfunction, but some PAH specialists prescribed the drug for off-label use to their patients. Anecdotal evidence was positive for many patients, prompting Pfizer to organize a number of clinical trials which would expand the use of and increase the demand for it's product.
Fda approval date
The differences between Viagra and Revatio are mostly superficial. Viagra is a blue and diamond-shaped tablet. Revatio is round and white. The dosing is different, but chemically they are the same. Both are oral medications. For treatment of PAH, this drug - in whatever form your doctor prescribes it - must be taken three or more times per day at equal intervals. It is important to take this drug as directed by your physician. You will probably begin at a low dose and be asked to build up to a target maintenance level.
In November 2009, the FDA also approved a liquid form of Revatio for injection:
"The FDA has approved Revatio (sildenafil, from Pfizer) injection, an intravenous phosphodiesterase-5 (PDE-5) inhibitor, for the treatment of adults with pulmonary arterial hypertension (PAH) (WHO Group I) to improve exercise ability and delay clinical worsening. Revatio injection is for the continued treatment of patients with PAH who are currently prescribed Revatio tablets but who are temporarily unable to take oral medication."
Source: Monthly Processing Reference
When you are being evaluated as a candidate for this medication, your doctor may have you come into his office or clinic so that your blood pressure can be monitored. Revatio may cause a drop in your systemic blood pressure so care will be taken to ensure your blood pressure does not drop to an unsafe level. If you feel dizzy at any time while you are taking this medication, you should notify your doctor. If you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw while taking this medication, call your doctor right away. You could be having a serious side effect of Revatio.
The most common adverse reactions include epistaxis, headache, dyspepsia, flushing, insomnia, erythema, dyspnea, and rhinitis.
Revatio should never be taken in combination with organic nitrates
Studies in vitro have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, > 80-fold for PDE1, > 700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11). The approximately 4,000-fold selectivity for PDE5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10-fold as potent for PDE5 compared to PDE6, an enzyme found in the retina and involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels.
In addition to pulmonary vascular smooth muscle and the corpus cavernosum, PDE5 is also found in other tissues including vascular and visceral smooth muscle and in platelets. The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet anti-aggregatory activity of nitric oxide observed in vitro, and the mild peripheral arterial-venous dilatation in vivo.
The cost of Revatio is about $10,000 per year.
Now that sildenafil citrate has been approved to treat PAH, your insurance company should cover the cost of your medication. For those of you with no drug coverage or a high co-payment, you may want to ask your physician if he or she can prescribe Viagra as the price of Viagra has dropped due to competition in the marketplace.
Page Reviewed/Edited: November 2010
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- October 29, 2012
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- October 7, 2012
- Survival of Japanese Patients with PAH after the Introduction of ERA and/or PDE-5 Inhibitors
- September 30, 2012
- FDA Safety Changes: Off-Label Use of Sildenafil Not Recommended in Children With PAH
- August 24, 2012
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- May 6, 2012
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- April 23, 2012
- Erectile Dysfunction Drug Seizure
- March 23, 2012
- Argentine province to produce Sildenfil for ED and PH use
- March 1, 2012
- Sildenafil for Chronic Obstructive Pulmonary Disease: A Randomized Crossover Trial.
- February 23, 2012
- Ocular safety of sildenafil citrate when administered chronically for pulmonary arterial hypertension: results from phase III, randomised, double masked, placebo controlled trial and open label extension.
- February 18, 2012
- Phosphodiesterase 5 Inhibition With Sildenafil Reverses Exercise Oscillatory Breathing in Chronic Heart Failure
- February 9, 2012
- Treatment with sildenafil and treprostinil allows successful liver transplantation of patients with moderate to severe portopulmonary hypertension.
- November 15, 2011
- Sildenafil Found Beneficial in Pediatric PAH
- November 13, 2011
- Sildenafil Treats Pediatric Pulmonary Hypertension
- October 7, 2011
- PAH in pediatric patients: Sildenafil increases mortality
- October 3, 2011
- Chinese trial estimates the impact of sildenafil on survial in patients with PAH
- September 29, 2011
- Pfizer, pharmacy group warn on counterfeit drugs
- September 23, 2011
- Sildenafil appears safe and effective for Eisenmenger syndrome
- August 21, 2011
- Pfizer Wins Viagra Patent Battle Against Teva
- May 5, 2011
- The European Commission Approves Pfizer’s Revatio®
- March 10, 2011
- Exercise Performance in Children and Young Adults with Single Ventricle Heart Disease Improves with SIldenafil
- March 8, 2011
- Sildenafil helped woman with Raynaud’s syndrome
- February 14, 2011
- A Phase III, Multicenter, Collaborative, Open-Label Clinical Trial of Sildenafil in Japanese Patients With Pulmonary Arterial Hypertension
- January 3, 2011
- Score One for the FDA as Rest of World Finally Yanks Thelin
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- Viagra for Prostate Cancer? 10 Multi-Use Drugs
- May 20, 2010
- Safety of sildenafil citrate: review of 67 double-blind placebo-controlled trials and the postmarketing safety database
- May 19, 2010
- Men who take Viagra and other sex aid drugs double their risk of hearing loss: study
- April 27, 2010
- Standard PAH therapy improves long term survival in CTEPH patients.
- February 23, 2010
- Sildenafil Helps Young Patients with Single-Ventricle Disease
- December 18, 2009
- Sildenafil for Pulmonary Hypertension Increases Pain Crises in Sickle Cell Patients
- October 7, 2009
- Simvastatin and sildenafil combine to attenuate pulmonary hypertension
- October 6, 2009
- Viagra Could Prevent Unhealthy Heart Growth