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Drugs reference index «Sildenafil Citrate»

Sildenafil Citrate

Sildenafil Citrate

Pronunciation: (sill-DEN-ah-fil)Class: Phosphodiesterase type-5 inhibitor

Trade Names:Revatio- Tablets 20 mg

Trade Names:Viagra- Tablets 25 mg- Tablets 50 mg- Tablets 100 mg



Enhances the effect of nitric oxide by inhibiting phosphodiesterase type-5 (PDE5) in the corpus cavernosum of the penis. This results in vasodilation, increased inflow of blood into the corpus cavernosum, and ensuing penile erection upon sexual stimulation.


Inhibits cGMP-specific PDE5 in the smooth muscle of the pulmonary vasculature, where PDE5 is responsible for degradation of cGMP. This increases cGMP within pulmonary vascular smooth muscle cells resulting in relaxation leading to vasodilation of the pulmonary vascular bed in patients with pulmonary hypertension.



Bioavailability is 40%. T max is 30 to 120 min (mean, 60 min). The drug is rapidly absorbed; when taken with a high-fat meal, the absorption rate is reduced with a mean delay in T max of 60 min and a mean reduction of C max of 29%.


Vd is 105 L; 96% bound to plasma proteins.


Undergoes hepatic metabolism (mainly CYP-450 3A4). The major circulating metabolite results from N-desmethylation.


The t ½ is 4 h. The drug is cleared primarily by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes, and is excreted primarily in feces (approximately 80%) and, to a lesser extent, in urine (approximately 13%).


Duration of action is up to 4 h.

Special Populations

Renal Function ImpairmentViagra

Severe renal function impairment is associated with increased plasma levels. Consider a starting dose of 25 mg.

Hepatic Function ImpairmentViagra

Hepatic function impairment is associated with increased plasma levels. Consider a starting dose of 25 mg.


Age older than 65 yr is associated with increased plasma levels. Consider a starting dose of 25 mg.

Indications and Usage

Treatment of erectile dysfunction ( Viagra ); treatment of pulmonary arterial hypertension to improve exercise ability ( Revatio ).


Patients using any type of organic nitrates (eg, dinitrate, isosorbide mono, nitroglycerin)

Enhanced effects leading to prolonged hypotension; hypersensitivity.

Dosage and Administration

Erectile Dysfunction ( Viagra only)Adults

PO 50 mg once, 0.5 to 4 h prior to sexual activity. Titration to a 25- or a 100-mg dose may be used based on tolerability or efficacy. The max recommended use is once daily.

Dosage Adjustments ( Viagra only)Adults

PO Consider a starting dose of 25 mg in patients older than 65 yr of age, or in patients with hepatic function impairment, severe renal function impairment, or concurrent use of potent CYP-450 3A4 inhibitors (eg, erythromycin, itraconazole, ketoconazole, saquinavir).


Do not take sildenafil 50 or 100 mg within 4 h of alpha-blocker administration; however, a dose of sildenafil 25 mg may be taken at any time.

Protease inhibitors

Do not exceed a max single dose of sildenafil 25 mg in a 48-h period.

Pulmonary Arterial Hypertension ( Revatio only)Adults

PO 20 mg 3 times daily.

General Advice

  • Administer without regard to meals. Administer with food if GI upset occurs.
  • Revatio
  • Administer doses approximately 4 to 6 h apart.


Store at controlled room temperature (59° to 86°F).

Drug Interactions

Alpha-blockers, amlodipine (eg, doxazosin)

Administration may result in an additional decrease in BP.

Grapefruit juice

Sildenafil plasma concentrations may be prolonged; however, data are conflicting.

HMG-CoA reductase inhibitors (eg, simvastatin)

At least 1 case of rhabdomyolysis has been reported during coadministration of sildenafil and simvastatin.

Inducers of CYP3A4 (eg, rifampin)

May decrease sildenafil levels.

Inhibitors of CYP3A4 (eg, cimetidine, erythromycin, itraconazole, ketoconazole, protease inhibitors [eg, ritonavir, saquinavir], tacrolimus)

Sildenafil plasma levels may be elevated, increasing the risk of adverse reactions.


Hypotension (see Contraindications).

Opioid analgesics (eg, dihydrocodeine)

Effects of sildenafil may be prolonged, resulting in prolonged erections following orgasm.

Laboratory Test Interactions

None well documented.

Adverse Reactions


Abnormal ECG, angina pectoris, AV block, cardiac arrest, cardiomyopathy, cerebral thrombosis, heart failure, hypotension, myocardial ischemia, palpitation, postural hypotension, syncope, tachycardia (less than 2%); cerebrovascular hemorrhage, hypertension, MI, pulmonary hemorrhage, subarachnoid and intracerebral hemorrhages, sudden cardiac death, transient ischemic attack, ventricular arrhythmia (postmarketing).


Headache (16%); dizziness (2%); abnormal dreams, ataxia, decreased reflexes, depression, hypertonia, hypesthesia, insomnia, migraine, neuralgia, neuropathy, paresthesia, somnolence, tremor, vertigo (less than 2%); anxiety, seizure (postmarketing).


Flushing (10%); rash (2%); contact dermatitis, exfoliative dermatitis, herpes simplex, pruritus, skin ulcer, sweating, urticaria (less than 2%).


Nasal congestion (4%); abnormal vision (mild and transient, predominantly color tinge vision, increased sensitivity to light or blurred vision [3%]); cataract, conjunctivitis, deafness, dry eyes, ear pain, eye hemorrhage, eye pain, mydriasis, photophobia, tinnitus (less than 2%); bloodshot appearance, diplopia, epistaxis, increased IOP, ocular burning, ocular redness, ocular swelling/pressure, paramacular edema, retinal vascular disease or bleeding, temporary vision loss/decreased vision, vitreous detachment/traction (postmarketing).


Dyspepsia (7%); diarrhea (3%); colitis, dry mouth, dysphagia, esophagitis, gastritis, gastroenteritis, gingivitis, glossitis, rectal hemorrhage, stomatitis, vomiting (less than 2%).


UTI (3%); abnormal ejaculation, anorgasmia, breast enlargement, cystitis, genital edema, nocturia, urinary frequency, urinary incontinence (less than 2%); hematuria, priapism, prolonged erection (postmarketing).


Anemia, leukopenia (less than 2%).


Abnormal LFTs (less than 2%).


Edema, gout, hyperglycemia, hypernatremia, hyperuricemia, hypoglycemic reaction, peripheral edema, thirst, unstable diabetes.


Arthritis, arthrosis, bone pain, myalgia, myasthenia, synovitis, tendon rupture, tenosynovitis.


Asthma, bronchitis, dyspnea, increased cough, increased sputum, laryngitis, pharyngitis, sinusitis (less than 2%).


Abdominal pain, accidental falls, accidental injury, allergic reaction, asthenia, chest pain, chills, face edema, pain, photosensitivity, shock (less than 2%).



Category B .




Safety and efficacy not established.



Dose selection should be cautious, usually starting at the lower end of the dosing range, reflecting the greater frequency of decreased hepatic and renal function and comorbidity.


Consider initial dose of 25 mg in patients older than 65 yr of age.

Renal Function


No dose adjustments are required for renal function impairment (CrCl less than 30 mL/min).


Consider initial dose of 25 mg in patients with severe renal function impairment (CrCl less than 30 mL/min).

Hepatic Function


No dose adjustments are required for Child Pugh class A or B hepatic function impairment.


Consider initial dose of 25 mg in patients with hepatic function impairment.


Use caution when PDE5 inhibitors are coadministered with alpha-blockers because of risk of additive reduction in BP leading to symptomatic hypotension. Viagra doses greater than 25 mg should not be taken within 4 h of taking an alpha-blocker; a dose of Viagra 25 mg may be taken at any time.

Anatomical deformation of the penis

Use Viagra with caution in patients with anatomical deformation of the penis (eg, angulation, cavernosal fibrosis, Peyronies disease) or patients prone to priapism (eg, leukemia, multiple myeloma, sickle cell anemia).

Bleeding disorders/active peptic ulceration

Safety of sildenafil is unknown in patients with bleeding disorders or active peptic ulceration.

Cardiac risk

Exertion from renewed sexual activity may pose a risk of cardiac events such as cerebrovascular hemorrhage, hypertension, MI, sudden cardiac death, transient ischemic attack, and ventricular arrhythmia.

Concurrent medical conditions

Safety and efficacy have not been established for the use of sildenafil in the following situations: patients who have experienced MI, stroke, or life-threatening arrhythmia in last 6 mo; patients with cardiac failure or coronary artery disease causing unstable angina; patients with resting hypotension (BP less than 90/50) or hypertension (BP greater than 170/110); patients with retinitis pigmentosa; patients currently on bosentan therapy. Use with caution if sildenafil is prescribed in any of these situations.

Pulmonary veno-occlusive disease (PVOD)

Pulmonary vasodilators may significantly worsen CV status of patients with PVOD. Administration of Revatio to such patients is not recommended. Consider the possibility of PVOD if signs of pulmonary edema occur when Revatio is administered.


Prior to starting sildenafil, carefully consider whether patients with certain underlying conditions (eg, resting hypotension [BP less than 90/50], fluid depletion, severe left ventricular outflow obstruction, autonomic dysfunction) could be adversely affected by vasodilatory effects.



No data available.

Patient Information

  • Advise patient to review the patient information leaflet carefully before starting therapy and to read and check for new information each time the medication is refilled.
  • Review dosing schedule with patient.
  • Advise patient to take prescribed dose without regard to meals but to take with food if stomach upset occurs.
  • Caution patient not to stop taking or change the dose unless advised by health care provider.
  • Instruct patient to stop using and contact health care provider immediately if any of the following occur: chest pain, dizziness, erection persisting longer than 4 h, fainting, painful erection, or sudden loss of vision in 1 or both eyes.
  • Revatio
  • Advise patient to take prescribed dose 3 times daily, separating doses by at least 4 to 6 h.
  • Viagra
  • Advise patient that medication may be most effective if taken approximately 60 min before anticipated sexual activity, but that medication can be taken anywhere from 30 min to 4 h before sexual activity.
  • Caution patient not to take more than 1 dose in a 24-h period.
  • Advise patient that sexual stimulation will be required for medication to work and an erection to occur.
  • Caution patient who is taking sildenafil 50 or 100 mg and an alpha-blocker to take sildenafil at least 4 h before or after the alpha-blocker. Advise patient that a dose of Viagra 25 mg can be taken at any time.
  • Advise patient to contact health care provider if not satisfied with sexual performance after taking medication or if bothersome adverse reactions occur.
  • Caution patient to avoid using poppers (eg, amyl nitrate, butyl nitrate) while taking this medication.
  • Caution patient that medication is not a form of birth control nor does it provide protection against STDs and to use protective measures as indicated.

Copyright © 2009 Wolters Kluwer Health.

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