G04BE03 - Sildenafil |
Propably not porphyrinogenic |
PNP |
Rationale
Sildenafil is a substrate for CYP 3A4 and 2C9 and is a weak inhibitor of CYP 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4. Clinical studies have shown no significant potential for CYP 3A4 or 2C9 induction or inhibition.
Chemical description
Sildenafil is a phosphodiesterase type-5 inhibitor.
Therapeutic characteristics
Sildenafil is a vasoactive agent used to treat erectile dysfunction, and can also be used to reduce symptoms in patients with pulmonary arterial hypertension (PAH). It is administered orally or intravenously.
Metabolism and pharmakokinetics
Sildenafil is metabolized by N-demethylation, mainly by CYP3A4 but also to some extent by CYP2C9. Elimination half-life is 3-5 hours. In vitro studies has show that Sildenafil is a weak inhibitor of the cytochrome P450 isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4. Interaction studies have shown no significant alteration in the activities of CYP 3A4 or 2C9.
References
- Scientific articles
- Hyland R, Roe EG et al. Identification of the cytochrome P450 enzymes involved in the N-demethylation of sildenafil. Br J Clin Pharmacol. 2001 Mar;51(3):239-48. PMID 11298070. #1562
- Warrington JS, Shader RI, et al. In vitro biotransformation of sildenafil (Viagra): identification of human cytochromes and potential drug interactions. Drug Metab Dispos. 2000 Apr;28(4):392-7. PMID 10725306. #4482
- Drug reference publications
- Sweetman SC, editor. Martindale: The complete drug reference. Sildenafil citrate. Pharmaceutical Press 2009. #1563
- Summary of Product Characteristics
- The electronic Medicines Compendium (emc). Summary of Product Characteristics (SPC). Viagra and Revatio. 02.05.2011). #1564
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