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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

Pharmacology

Viagra

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.

Revatio

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.

Pharmacokinetics

Absorption

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%.

Distribution

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

Metabolism

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

Elimination

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

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.

ElderlyViagra

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 ).

Contraindications

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).

Alpha-Blockers

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.

Storage/Stability

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.

Nitrates

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

Cardiovascular

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).

CNS

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).

Dermatologic

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

EENT

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).

GI

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

Genitourinary

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

Hematologic

Anemia, leukopenia (less than 2%).

Hepatic

Abnormal LFTs (less than 2%).

Metabolic

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

Musculoskeletal

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

Respiratory

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

Miscellaneous

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

Precautions

Pregnancy

Category B .

Lactation

Undetermined.

Children

Safety and efficacy not established.

Elderly

Revatio

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.

Viagra

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

Renal Function

Revatio

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

Viagra

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

Hepatic Function

Revatio

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

Viagra

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

Alpha-blockers

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.

Vasodilation

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.

Overdosage

Symptoms

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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