title: Incomplete recovery of erectile function in rat after discontinuation of dual 5-alpha reductase inhibitor therapy.
abstract: OBJECTIVE
  The association of 5-alpha reductase inhibitor (5ARI) therapy and sexual dysfunction has been reported. Some patients claim persistent erectile dysfunction despite long-term discontinuation of 5ARI treatment. The aim of this study was to assess erectile function after cessation of 5ARI therapy using a rat model.
  
  
  METHODS
  Twenty-six adult male Sprague-Dawley rats were randomized into three groups: (i) control (N = 10); (ii) 8-week dutasteride treatment (0.5 mg/rat/day, in drinking water, N = 8); and (iii) 6-week dutasteride treatment followed by a 2-week washout period (N = 8). The experiments were performed after 8 weeks from the initiation of treatment in all groups. In vivo erectile activity and in vitro contractile and relaxant responses of cavernosal smooth muscle were investigated.
  
  
  RESULTS
  In vivo erectile activity (intracavernosal pressure [ICP]/mean arterial pressure [MAP] and total ICP) in treatment groups were significantly decreased compared with controls (ICP/MAP: P < 0.001 for 2.5 v, 5 v, and 7.5 v; total ICP: P < 0.001 for 5 v and P < 0.01 for 7.5 v). Acetylcholine-induced relaxations were diminished in treatment groups (P < 0.05). Relaxant responses to electrical field stimulation (EFS) were decreased in the 8-week treatment group (P < 0.05) but were similar to controls in the washout group. Sodium nitroprusside (SNP)-induced endothelium-independent relaxations were reduced in the 8-week dutasteride treatment group (P < 0.01), while these responses were restored in the washout group. The contractile responses to the alpha1-adrenergic agonist phenylephrine were decreased in treatment groups compared with controls (P < 0.01). Direct neurogenic contractile responses in the dutasteride groups were significantly lower than controls between 1 and 15 Hz frequencies (but not at 20 Hz) and washout partially restored the responses at 10 and 15 Hz.
  
  
  CONCLUSIONS
  Discontinuation of dutasteride improved the relaxant responses to EFS and SNP, while cholinergic and adrenergic responses remained depressed. Our findings suggest a time-dependent detriment of dutasteride on erectile function. The withdrawal/washout effect of 5ARIs on parameters of human sexual function warrants further investigation.
authors.affiliation: Department of Urology, Ankara Numune Education and Research Hospital, Ankara, Turkey.
authors.forename: Cetin Volkan
authors.initials: CV
authors.lastname: Oztekin
authors.forename: Serap
authors.initials: S
authors.lastname: Gur
authors.forename: Nour A
authors.initials: NA
authors.lastname: Abdulkadir
authors.forename: Utku
authors.initials: U
authors.lastname: Lokman
authors.forename: Alp Özgür
authors.initials: AÖ
authors.lastname: Akdemir
authors.forename: Mesut
authors.initials: M
authors.lastname: Cetinkaya
authors.forename: Wayne J G
authors.initials: WJ
authors.lastname: Hellstrom
mesh_terms: D058891:5-alpha Reductase Inhibitors / Q000009:adverse effects*; D000818:Animals; D001378:Azasteroids / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D000068538:Dutasteride; D007172:Erectile Dysfunction / Q000139:chemically induced*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D010410:Penile Erection / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D000068538:Dutasteride