Drug information of Sildenafil
Sildenafil relaxes muscles and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women.
Mechanism of effect
Sildenafil is an inhibitor of cGMP specific phosphodiesterase type-5 (PDE-5) in the smooth muscle of the pulmonary vasculature, where PDE-5 is responsible for degradation of cGMP.
For the treatment of erectile dysfunction and to relieve symptoms of pulmonary arterial hypertension (PAH)
Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (25 to 63%).Sildenafil and its major circulating N-desmethyl metabolite are both approximately 96% bound to plasma proteins. Sildenafil is cleared predominantly by the CYP3A (major route) and cytochrome P450 2C9 (CYP2C9, minor route) hepatic microsomal isoenzymes. Both sildenafil and the active metabolite have terminal half-lives of about 4 hours. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).
Usual Adult Dose for Erectile Dysfunction Initial dose: 50 mg orally once a day, as needed, 1 hour prior to sexual activity Maintenance: 25 to 100 mg orally once a day, as needed, 1 hour prior to sexual activity Usual Geriatric Dose for Erectile Dysfunction Initial dose: 25 mg orally once a day 1 hour prior to sexual activity.
Drug contraindicationshypersensitivity to drug or its components. , with nitrates and nitric oxide donors
Side effectsnausea , Headache , insomnia , vomiting , Seizures , rash , flushing , Diarrhea , Dyspnea , Erythema , paresthesia , Rhinitis , dyspepsia , Urinary tract infection , edema , sinusitis , fever , myalgia , gastritis , pain in the extremities , Cardiovascular disorder , Epistaxis , Visual abnormalities
InteractionsAlprostadil , Bosentan , Tolterodine , Dexamethasone , Ciprofloxacin , Erythromycin , Itraconazole , isosorbide dinitrate , Terazosin , Cimetidine , Nitroglycerin , Voriconazole , Ketoconazole , Clarithromycin , Fluticasone propinate , Phenoxybenzamine , Methyldopa , Disulfiram , Bisoprolol , Nitroprusside sodium , Rifabutin , Rifapentine , Darunavir , Doxazosin , ritonavir , isosorbide mononitrate , saquinavir , nelfinavir , Indinavir , Amyl Nitrite , Telaprevir , Etravirine , Dabrafenib , cobicistat , Delavirdine , Alfuzosin , Troleandomycin , riociguat , sitaxentan , Ombitasvir, Paritaprevir, and Ritonavir , Nesiritide
1-Use of sildenafil, particularly chronic use, is not recommended in children. 2-carefully consider whether patients with certain underlying conditions could be adversely affected by such vasodilatory effects (e.g., patients on antihypertensive therapy or with resting hypotension [BP less than 90/50], fluid depletion, severe left ventricular outflow obstruction, or autonomic dysfunction). Monitor blood pressure when coadministering blood pressure lowering drugs with sildenafil. 3-Pulmonary vasodilators may significantly worsen the cardiovascular status of patients with pulmonary veno-occlusive disease (PVOD). 4-Use sildenafil with caution in patients with anatomical deformation of the penis (e.g., angulation, cavernosal fibrosis, or Peyronie’s disease) or in patients who have conditions, which may predispose them to priapism (e.g., sickle cell anemia, multiple myeloma, or leukemia). In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance.
Points of recommendation
1-Advise patients to seek prompt medical attention in the event of sudden decrease or loss of hearing while taking sildenafil. These events may be accompanied by tinnitus and dizziness. 2-Advise patients to seek immediate medical attention for a sudden loss of vision in one or both eyes while taking sildenafil. Such an event may be a sign of NAION. 3- Advise patients taking sildenafil not to take VIAGRA or other PDE-5 inhibitors.