Sildenafil Citrate (5 brand names, 5 dosage forms, 2 routes)
Available dosage forms: TABLET, SUSPENSION, FOR SUSPENSION, FILM, SOLUTION.
Routes of administration: ORAL, INTRAVENOUS.
Brand Names
- LIQREV
- REVATIO
- SILDENAFIL CITRATE
- VIAGRA
- VYBRIQUE
Indications and Usage
Adults Sildenafil injection is indicated for the treatment of pulmonary arterial hypertension (PAH) (World Health Organization [WHO] Group I) in adults to improve exercise ability and delay clinical worsening [see Clinical Studies (14)]. Pediatric Patients (1 to 17 Years Old) Sildenafil injection is indicated in pediatric patients 1 to 17 years old for the treatment of pulmonary arterial hypertension (PAH) (WHO Group I) to improve exercise ability and, in pediatric patients too young to perform standardized exercise testing, pulmonary hemodynamics thought to underlie improvements in exercise [see Clinical Studies (14)].
Contraindications
Sildenafil is contraindicated in patients with: Concomitant use of organic nitrates in any form, either regularly or intermittently, because of the greater risk of hypotension [see Warnings and Precautions (5.1)]. Concomitant use of riociguat, a guanylate cyclase stimulator. Phosphodiesterase-5 (PDE-5) inhibitors, including sildenafil, may potentiate the hypotensive effects of riociguat. Known hypersensitivity to sildenafil or any component of the injection. Hypersensitivity, including anaphylactic reaction, anaphylactic shock and anaphylactoid reaction, has been reported in association with the use of sildenafil.
Adverse Reactions
The following serious adverse events are discussed elsewhere in the labeling: Hypotension [see Warnings and Precautions (5.1)] Vision Loss [see Warnings and Precautions (5.4)] Hearing Loss [see Warnings and Precautions (5.5)] Priapism [see Warnings and Precautions (5.7)] Vaso-occlusive Crisis in Patients with Pulmonary Hypertension Secondary to Sickle Cell Disease [see Warnings and Precautions (5.8)]
Drug Interactions
Nitrates Concomitant use of sildenafil with nitrates in any form is contraindicated [see Contraindications (4)]. Strong CYP3A Inhibitors Concomitant use of sildenafil with strong CYP3A inhibitors is not recommended [see Clinical Pharmacology (12.3)]. Moderate-to-Strong CYP3A Inducers Concomitant use of sildenafil with moderate-to-strong CYP3A inducers (such as bosentan) decreases the sildenafil exposure. Dose up-titration of sildenafil may be needed when initiating treatment with moderate-to-strong CYP3A inducers. Reduce the dose of sildenafil to 20 mg three times a day when discontinuing treatment with moderate-to-strong CYP3A inducers [see Clinical Pharmacology (12.3) and Clinical Studies (14)].
Mechanism of Action
Sildenafil is an inhibitor of cGMP specific PDE-5 in the smooth muscle of the pulmonary vasculature, where PDE-5 is responsible for degradation of cGMP. Sildenafil, therefore, increases cGMP within pulmonary vascular smooth muscle cells resulting in relaxation. In patients with PAH, this can lead to vasodilation of the pulmonary vascular bed and, to a lesser degree, vasodilatation in the systemic circulation. 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, greater than 80-fold for PDE1, greater than 700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11). The approximately 4,000-fold selectivity for PDE-5 versus PDE3 is important because PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10 times 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 [see Clinical Pharmacology (12.2)]. 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.
Overdosage
In studies with healthy volunteers of single doses up to 800 mg, adverse events were similar to those seen at lower doses but rates and severities were increased. In cases of overdose, standard supportive measures should be adopted as required. Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and it is not eliminated in the urine.