title: Do food and dose timing affect the efficacy of sildenafil? A randomized placebo-controlled study.
abstract: BACKGROUND
  Sildenafil citrate has been used worldwide by men with erectile dysfunction. The prescribing information for sildenafil suggests ingestion 1 hour before sexual activity and also notes reduced maximum plasma concentration and delayed time to maximum concentration following ingestion with a high-fat meal. The clinical impact of coingestion of food and these factors has never been evaluated.
  
  
  OBJECTIVE
  To determine, using a naturalistic study design, whether sildenafil taken 1 hour before or during a meal compared with usual ingestion 30-60 minutes before sexual activity affects efficacy or patient satisfaction.
  
  
  METHODS
  After a 1-2-week washout, 48 men (29-79 years old), currently satisfied with sildenafil, followed each of four regimens: (A) sildenafil 1 hour before a meal and placebo 30-60 minutes before planned coitus vs. (B) placebo 1 hour before a meal and sildenafil 30-60 minutes before coitus; and (C) sildenafil during a meal and placebo 30-60 minutes before coitus vs. (D) placebo during a meal and sildenafil 30-60 minutes before coitus. Subjects were not instructed to change their regular dietary habits during the course of the study.
  
  
  METHODS
  Change from baseline in the International Index of Erectile Function (IIEF) Erectile Function (EF) domain score, responses to Sexual Encounter Profile (SEP) questions 2 (erection sufficient for penetration) and 3 (erection sufficient to complete intercourse), and measures of patient preference and satisfaction.
  
  
  RESULTS
  Mean changes in IIEF-EF domain scores were 11.4 for regimens A and B and 11.2 for C and D. Positive SEP2 responses were recorded for 93.9% and 91.8% of intercourse attempts in A and B and 91.4% and 92.6% in C and D. Corresponding results for SEP3 were 84.7% and 85.9%, and 83.4% and 87.5%, respectively. There were no significant differences between pairs of treatments on satisfaction. The time between sildenafil ingestion and intercourse attempt (0-0.5 to >10 hours) had no significant effect on responses to SEP2, but decreased responses to SEP3 from a maximum of 92.8% at 1.5-2 hours to 81.6% at more than 10 hours (P = 0.003).
  
  
  CONCLUSIONS
  No significant loss of efficacy occurs when sildenafil is taken shortly before or with a meal. The duration of action for sildenafil may exceed 10 hours.
authors.affiliation: Western Clinical Research, Inc., Torrance, CA, USA. Electronic address: wewedoc@aol.com.
authors.forename: Norman
authors.initials: N
authors.lastname: Zinner
mesh_terms: D000328:Adult; D000368:Aged; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D007172:Erectile Dysfunction / Q000188:drug therapy*; D018565:Food-Drug Interactions; D006801:Humans; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D010410:Penile Erection / Q000187:drug effects; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage*; D010879:Piperazines / Q000008:administration & dosage*; D011687:Purines / Q000008:administration & dosage; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000008:administration & dosage*; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000008:administration & dosage*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate