Erectile dysfunction
Erectile dysfunction is a condition in which a male cannot obtain or maintain an erect penis.[1][2] It can result from several medical conditions, including diabetes, radical prostatectomy, vascular insufficiency, nerve damage, or insufficient cyclic guanine monophosphate (cGMP) levels.
Treatment
Phosphodiesterase type 5 inhibitors
Sildenafil (Viagra®), vardenafil (Levitra®) and tadalafil (Cialis®), may treat ED[3] and as well as pulmonary hypertensive, are selective phosphodiesterase type 5 (PDE-5) inhibitors that bind selectively to PDE-5 and inhibit the binding and subsequent degradation of cGMP. Normally, erection results from increased cGMP levels produced by guanylate cyclase, which in turn is upregulated by nitric oxide release after stimulation. By decreasing the degradation of cGMP by PDE-5 enzymes increases the levels of cGMP in the corpus cavernosum and its supply vessels, relaxes the smooth muscle, and enables an erection. Viagra (sildenafil) was the first blockbuster drug for ED treatment in this class, although vardenafil is more potent in vitro. Both sildenafil and vardenafil have structural similarity to cGMP (and the unselective PDE inhibitor caffeine), with which they compete for binding of PDE-5 enzymes. Tadalafil is significantly different in structure but is thought to act by the same mechanism.
83% of men who used sildenafil had at least one episode of intercourse as compared to 45% who received placebo according to a systematic review of randomized controlled trials of using sildenafil.[4] Few randomized controlled trials have compared the different phosphodiesterase inhibitors.[5][6][7][8]
References
- ↑ Corbin JD, Francis SH (2003). "Molecular biology and pharmacology of PDE-5-inhibitor therapy for erectile dysfunction". J. Androl. 24 (6 Suppl): S38–41. PMID 14581493. [e]
- ↑ McVary KT (December 2007). "Clinical practice. Erectile dysfunction". N. Engl. J. Med. 357 (24): 2472–81. DOI:10.1056/NEJMcp067261. PMID 18077811. Research Blogging.
- ↑ Moore RA, Derry S, McQuay HJ (2005). "Indirect comparison of interventions using published randomised trials: systematic review of PDE-5 inhibitors for erectile dysfunction". BMC Urol 5: 18. DOI:10.1186/1471-2490-5-18. PMID 16354303. PMC 1343572. Research Blogging.
- ↑ Fink HA, Mac Donald R, Rutks IR, Nelson DB, Wilt TJ (June 2002). "Sildenafil for male erectile dysfunction: a systematic review and meta-analysis". Arch. Intern. Med. 162 (12): 1349–60. PMID 12076233. [e]
- ↑ Govier F, Potempa AJ, Kaufman J, Denne J, Kovalenko P, Ahuja S (November 2003). "A multicenter, randomized, double-blind, crossover study of patient preference for tadalafil 20 mg or sildenafil citrate 50 mg during initiation of treatment for erectile dysfunction". Clin Ther 25 (11): 2709–23. PMID 14693299. [e]
- ↑ Rubio-Aurioles E, Porst H, Eardley I, Goldstein I (November 2006). "Comparing vardenafil and sildenafil in the treatment of men with erectile dysfunction and risk factors for cardiovascular disease: a randomized, double-blind, pooled crossover study". J Sex Med 3 (6): 1037–49. DOI:10.1111/j.1743-6109.2006.00310.x. PMID 17100937. Research Blogging.
- ↑ Tolrà JR, Campaña JM, Ciutat LF, Miranda EF (September 2006). "Prospective, randomized, open-label, fixed-dose, crossover study to establish preference of patients with erectile dysfunction after taking the three PDE-5 inhibitors". J Sex Med 3 (5): 901–9. DOI:10.1111/j.1743-6109.2006.00297.x. PMID 16942534. Research Blogging.
- ↑ Martin-Morales A, Haro JM, Beardsworth A, Bertsch J, Kontodimas S (February 2007). "Therapeutic effectiveness and patient satisfaction after 6 months of treatment with tadalafil, sildenafil, and vardenafil: results from the erectile dysfunction observational study (EDOS)". Eur. Urol. 51 (2): 541–50; discussion 550. DOI:10.1016/j.eururo.2006.09.027. PMID 17084518. Research Blogging.