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Sildenafil (Viagra) Indications and Dosage
altitude sickness †
anorgasmy †
erectile dysfunction (ED)
pulmonary hypertension
Raynaud’s phenomenon †
sexual dysfunction †
† non-FDA-approved indication
Sildenafil (Viagra) Indications and Dosage
For the treatment of erectile dysfunction (ED) (impotence):
Oral dosage:
Adults: 50 mg PO, approximately 1 hour before sexual activity, up to once daily. The dose may be taken from 0.5 - 4 hours prior to sexual activity. Increase up to 100 mg or decrease to 25 mg based on clinical response. Maximum dosing frequency is once daily.
Adults at any age with hepatic cirrhosis or severe renal impairment, or patients receiving potent cytochrome P450 3A4 inhibitors (e.g., erythromycin, ritonavir, ketoconazole, itraconazole, saquinavir) concomitantly: 25 mg PO, approximately 1 hour prior to sexual activity, up to once daily. In patients receiving sildenafil with ritonavir, the maximum dosing frequency is every 48 hours.
Elderly: 25 mg PO, approximately 1 hour prior to sexual activity, up to once daily.
For the treatment of anorgasmy † or sexual dysfunction † in patients receiving antidepressant therapy:
for the treatment of sexual dysfunction † in females receiving antidepressant therapy:
Oral dosage:
Adult females: In open-label studies of women with sexual dysfunction due to antidepressant therapy, improvements were reported following 50 mg PO given 60 - 90 minutes prior to sexual activity. If a partial response was noted with the initial dose, some patients were instructed to increase the dose to 100 mg PO.
for the treatment of sexual dysfunction † in males receiving antidepressant therapy:
Oral dosage:
Adult males: A prospective, parallel-group, double-blind study involving 90 men evaluated the efficacy of sildenafil in improving sexual dysfunction associated with antidepressant therapy (i.e., selective and non-selective serotonin reuptake inhibitors). During the 6 week study, patients were randomly assigned to receive sildenafil at a flexible dose starting at 50 mg and adjusted to 100 mg before sexual activity or placebo; 89 patients completed the study. Sildenafil significantly improved erectile function, arousal, ejaculation, orgasm, and overall sexual satisfaction compared to patients receiving placebo.
For the treatment of pulmonary hypertension:
Oral dosage:
Adults: 20 mg PO three times per day. It is recommended that doses be taken approximately 4 - 6 hours apart, with or without food. In clinical trials, sildenafil improved exercise capacity, WHO functional class, and hemodynamics; no greater efficacy was achieved with the use of higher doses.
for the treatment of severe pulmonary hypertension † :
Oral dosage:
Adults: The effects of inhaled nitric oxide (NO), a single oral sildenafil dose, and the combination of oral sildenafil and inhaled NO were compared consecutively in 13 patients with severe pulmonary hypertension. Patients first received inhaled NO (10, 20, 40, and 80 ppm, each for 10 minutes); complete hemodynamics were taken at the most effective dose (80 ppm) in most patients. Nitric oxide was then stopped and, after 10 minutes, a single dose of sildenafil 75 mg PO was given. Monitoring occurred for 50 minutes with continuos ECG and arterial and pulmonary artery pressures; complete hemodynamics were recorded at 50 minutes (peak hemodynamic effects of sildenafil occur at about 50 minutes). One hour after sildenafil, inhaled NO was readministered. The results showed sildenafil was superior to NO in decreasing the mean pulmonary artery pressure and was equally effective and selective in reducing pulmonary vascular resistance. Sildenafil also caused a significant increase in the cardiac index whereas NO had no effect. Further, sildenafil decreased pulmonary artery wedge pressure (PAWP), while NO increased PAWP. The combination had additive vasodilatory effects in pulmonary circulation but not the systemic circulation. Additional studies are required to determine the maximal duration of effect, the pharmacokinetics, and the safety of sildenafil in patients with pulmonary hypertension.
for childhood primary pulmonary hypertension † :
Oral dosage:
Children † : Oral sildenafil was administered to a 4 year girl diagnosed with primary pulmonary hypertension and who had a poor response to prostacyclin infusions. The initial dose was 2 mg/kg PO four times per day. A 10% average increase in mixed venous oxygen saturation was noted after sildenafil administration. This increase lasted for 60 to 90 minutes. The dose frequency was then increased to every 4 hours. At 4 weeks follow-up, the patient continued to have improved exercise tolerance.
for severe pulmonary hypertension † in combination with iloprost:
Oral dosage:
Adults: The safety and efficacy of the combination of sildenafil and iloprost was evaluated in 30 patients with severe pulmonary hypertension (n=16), chronic thromboembolic pulmonary hypertension (n=13), or pulmonary hypertension due to aplasia of the left pulmonary artery (n=1). Following administration of nitric oxide and aerosolized iloprost and a 2-hour observation period, patients were randomized to receive either 12.5 mg sildenafil, 50 mg sildenafil, 12.5 mg sildenafil plus inhaled iloprost, or 50 mg sildenafil plus inhaled iloprost. The study results indicated that the regimen containing 50 mg PO of sildenafil plus inhaled iloprost was the most effective at reducing pulmonary vascular resistance. This regimen also was synergistic, meaning the effect on pulmonary resistance was greater than either 50 mg sildenafil alone or iloprost alone. The 12.5 mg sildenafil dose regimen was the least potent of the regimens. Overall, the combination of sildenafil and inhaled iloprost appears to be an effective regimen with vasodilatory effects lasting over 3 hours and with no serious adverse events.
for prevention of pulmonary hypertension † induced by altitude sickness † :
Oral dosage:
Adults: A small randomized double-blind placebo-controlled study evaluated the effectiveness of sildenafil on altitude-induced pulmonary hypertension and gas exchange in 12 healthy males. Six patients received sildenafil 40 mg PO or placebo 6 to 8 hours after arriving at altitude 4350 m (14,272 ft) then received sildenafil 40 mg PO or placebo three times daily for 6 days. Sildenafil protected against the development of altitude-induced pulmonary hypertension and improved gas exchange.
For the treatment of Raynaud’s phenomenon † :
Oral dosage:
Adults: A double-blind, placebo-controlled, crossover study evaluated sildenafil for symptomatic secondary Raynaud’s phenomenon resistant to vasodilatory therapy. Patients (n=18, 15 were female) were randomly assigned to receive placebo or sildenafil 50 mg PO twice daily for 4 weeks; a washout period of 1 week was used before crossover. The results showed that sildenafil significantly improved microcirculation and symptoms associated with Raynaud’s. In patients with chronic digital ulcerations, sildenafil treatment resulted in healing of trophic lesions which reappeared or progressed when sildenafil was stopped. Ulcerations did not heal while receiving placebo. Sildenafil therapy may be an alternative therapy in patients with Raynaud’s resistant to vasodilatory therapy.
Maximum Dosage Limits:
Adults: 100 mg/day PO.
Elderly: 100 mg/day PO.
Adolescents: Safe and effective use has not been established.
Children: Safe and effective use has not been established.
Patients with hepatic impairment:
Hepatic cirrhosis (Child-Pugh Class A and B): reduce starting dose to 25 mg PO (see Contraindications for hepatic disease).
Patients with renal impairment:
CrCl >= 30 ml/min: no dosage adjustment needed.
CrCl < 30 ml/min: reduce starting dose to 25 mg PO.
Intermittent hemodialysis:
Follow dosage adjustment for patients with CrCl < 30 ml/min. Further dosage adjustment for hemodialysis is not needed since sildenafil is highly bound to plasma proteins and is unlikely to be significantly removed by hemodialysis.
† non-FDA-approved indication
[ Last revised: 11/28/2005 1:40:00 PM ]
References
. Nurnberg HG, Hensley PL, Lauriello J, Parker LM, Keith SJ. Sildenafil for women patients with antidepressant-induced sexual dysfunction. Psychiatr Serv 1999;50:1076 - 8.
. Fava M, Rankin MA, Alpert JE, Nierenberg AA, Worthington JJ. An open trial of oral sildenafil in antidepressant-induced sexual dysfunction. Psychother Psychosom 1998;67:328 - 31.
. Abrams D, Schulze-Neick I, Magee AG. Sildenafil as a selective pulmonary vasodilator in childhood primary pulmonary hypertension. Heart 2000;84:E4.
. 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 - 22.
. 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.
. Nurnberg HG, Hensley PL, Gelenberg AJ, et al. Treatment of antidepressant-associated sexual dysfunction with sildenafil. JAMA 2003;289:56 - 64.
. Richalet JP, Gratadour P, Robach P, et al. Sildenafil Inhibits the altitude-induced hypoxemia and pulmonary hypertension. Am J Respir Crit Care Med. Published ahead of print on October 29, 2004 as doi:10.1164/rccm.200406-804OC on the Word Wide Web at http://ajrccm.atsjournals.org.
. Revatio™ (sildenafil citrate) package insert. New York, NY: Pfizer; 2005 Aug.
. Galie N, Ghofrani HA, Torbicki A. Sildenafil citrate therapy for pulmonary arterial hypertension. N Engl J Med 2005;353:2148 - 57.
. Fries R, Shariat K, von Wilmowsky H, et al. Sildenafil in the treatment of Raynaud’s phenomenon resistant to vasodilatory therapy. Circulation 2005;112:2980 - 5.
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