The efficacy and safety of oral sildenafil in Thai men with erectile dysfunction: a randomized, double-blind, placebo controlled, flexible-dose study

J Med Assoc Thai. 2003 Mar;86(3):195-205.


Objective: To evaluate the efficacy and safety of sildenafil citrate (Viagra) in a randomized, double-blind, placebo-controlled, flexible-dose study in Thai men with erectile dysfunction of broad-spectrum etiology and more than 6 months' duration.

Material and method: 125 patients aged 26 to 77 years were randomized at 4 centers in Thailand to receive either sildenafil citrate (50 mg initially, increased if necessary up to 100 mg or decreased to 25 mg depending on efficacy and/or tolerability) (n = 63) or a matching placebo (n = 62) taken on an 'as needed' basis approximately 1 hour prior to anticipated sexual activity for a period of 12 weeks. Efficacy was assessed by the patients' responses to the 15-question International Index of Erectile Function (IIEF), to questions on the event log of sexual activity, and to the global efficacy assessment question concerning improvement in erections.

Results: At the conclusion of the study, both the primary efficacy variables relating to the achievement and maintenance of erections sufficient for sexual intercourse and the secondary efficacy variables, which included the 5 separate domains of sexual functioning of the IIEF, the percentage of successful attempts at sexual intercourse, and the global efficacy assessment question concerning improvement in erections, were all significantly improved statistically by sildenafil in comparison with placebo except in the sexual desire domain which showed no difference. The percentage of successful attempts at sexual intercourse in the sildenafil group was 66.16 per cent while in the placebo group it was 33.05 per cent. The percentage of global efficacy assessment was improved in the sildenafil group by 82.5 per cent compared to 36.1 per cent in the placebo group. Adverse events considered treatment-related occurred in 19 patients (30.2%) receiving sildenafil and 7 (11.3%) receiving placebo. The most common adverse events with sildenafil were vasodilatation (flushing), headache, and dizziness, which occurred in 14.3 per cent, 6.3 per cent, and 6.3 per cent of patients respectively. All events were mild in nature.

Conclusions: Sildenafil is a safe and effective treatment for erectile dysfunction of broad-spectrum etiology in Thai men. Its efficacy appears similar to that reported in other studies in Western populations.

Publication types

  • Clinical Trial
  • Comparative Study
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Analysis of Variance
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Drug Administration Schedule
  • Erectile Dysfunction / diagnosis
  • Erectile Dysfunction / drug therapy*
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Piperazines / administration & dosage*
  • Probability
  • Purines
  • Reference Values
  • Sildenafil Citrate
  • Sulfones
  • Thailand
  • Treatment Outcome


  • Piperazines
  • Purines
  • Sulfones
  • Sildenafil Citrate