Overview
11 DESCRIPTION Sildenafil tablets, USP, an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Sildenafil citrate, is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1 H -pyrazolo[4,3- d ]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine...
Mechanism of Action
12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil enhances the effect of NO by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum.
Indications
- 1 INDICATIONS AND USAGE Sildenafil tablets are indicated for the treatment of erectile dysfunction. Sildenafil is a phosphodiesterase-5 (PDE5) inhibitor indicated for the treatment of erectile dysfunction (ED)
Common Doses
- 50 mg
- 100 mg
- 25 mg
- 30 mL
Dosage
2 DOSAGE AND ADMINISTRATION For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, sildenafil tablets may be taken anywhere from 30 minutes to 4 hours before sexual activity ( 2.1 ) Based on effectiveness and toleration, may increase to a maximum of 100 mg or decrease to 25 mg ( 2.1 ) Maximum recommended dosing frequency is once per day ( 2.1 ) 2.1 Dosage Information For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity.
Contraindications
- 4 CONTRAINDICATIONS Administration of sildenafil tablets to patients using nitric oxide donors, such as organic nitrates or organic nitrites in any form. Sildenafil tablets was shown to potentiate the hypotensive effect of nitrates ( 4.1 , 7.1 , 12.2 ) Known hypersensitivity to sildenafil or any component of tablet ( 4.2 ) Administration with guanylate cyclase (GC) stimulators, such as riociguat ( 4.3 ) 4.1 Nitrates Consistent with its known effects on the nitric oxide/cGMP pathway [ see Clinical Pharmacology (12.1 , 12.
Side Effects
- 6 ADVERSE REACTIONS The following are discussed in more detail in other sections of the labeling: Cardiovascular [ see Warnings and Precautions (5.1) ] Prolonged Erection and Priapism [ see Warnings and Precautions (5.2) ] Effects on the Eye [ see Warnings and Precautions (5.3) ] Hearing Loss [ see Warnings and Precautions (5.4) ] Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives [ see Warnings and Precautions (5.5) ] Adverse Reactions with the Concomitant Use of Ritonavir [ see Warnings and Precautions (5.
Interactions
- 7 DRUG INTERACTIONS Sildenafil can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) With concomitant use of alpha blockers, initiate sildenafil at 25 mg dose ( 2.3 ) CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, itraconazole, erythromycin): Increase sildenafil exposure ( 2.4 , 7.4 , 12.3 ) Ritonavir: Do not exceed a maximum single dose of 25 mg in a 48 hour period ( 2.4 , 5.6 ) Erythromycin or strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, saquinavir): Consider a starting dose of 25 mg ( 2.4 , 7.