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Clinical safety of oral sildenafil citrate (VIAGRATM) in the treatment of erectile dysfunction

International Journal of Impotence Research volume 10, pages 6974 (1998) | Download Citation



Sildenafil citrate has been shown to be effective in a wide range of patients with erectile dysfunction and has been approved in the United States for this indication. The overall clinical safety of oral sildenafil, a potent inhibitor of phosphodiesterase type 5, in the treatment of erectile dysfunction was evaluated in more than 3700 patients (with a total of 1631 years of exposure worldwide). Safety and tolerability data were analysed from a series of double-blind, placebo-controlled studies and from 10 open-label extension studies of sildenafil in the treatment of erectile dysfunction. A total of 4274 patients (2722 sildenafil, 1552 placebo; age range 19–87 y) received double-blind treatment over a period of up to six months’ duration, and 2199 received long-term, open-label sildenafil for up to 1 y. The most commonly reported adverse events (all causes) were headache (16% sildenafil, 4% placebo), flushing (10% sildenafil, 1% placebo), and dyspepsia (7% sildenafil, 2% placebo) and they were predominantly transient and mild or moderate in nature. These adverse events reflect the pharmacology of sildenafil as a phosphodiesterase type 5 inhibitor. No cases of priapism were reported. The rate of discontinuation due to adverse events (all causes) was comparable for patients treated with sildenafil (2.5%) and placebo (2.3%). In open-label extension studies, 90% of patients completed long-term sildenafil treatment, with only 2% withdrawing due to adverse events. Sildenafil is a well-tolerated oral treatment for erectile dysfunction.

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  1. Department of Urology, Queen’s University, Kingston General Hospital, Kingston, Ontario, Canada

    • A Morales
  2. Urology Department, Southmead Hospital, Bristol, UK

    • C Gingell
  3. Pfizer Central Research, Sandwich, UK

    • M Collins
    •  & IH Osterloh
  4. Pfizer Central Research, Groton, Connecticut, USA

    • PA Wicker


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Correspondence to A Morales.

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