Side-effect profile of sildenafil citrate (Viagra) in clinical practice

Urology. 2000 Sep 1;56(3):474-6. doi: 10.1016/s0090-4295(00)00649-x.


Objectives: Sildenafil citrate (Viagra) has been shown to be an effective treatment for erectile dysfunction. Initial studies reported a high tolerability and low incidence of certain characteristic adverse reactions. We sought to evaluate the incidence of side effects of sildenafil citrate, independent of industry support and constraints, utilizing a heterogeneous cohort of patients from a university-based practice.

Methods: A prospective, open-label, flexible-dose study of 256 patients treated with sildenafil citrate for erectile dysfunction was performed at a single institution. The patients were questioned explicitly about the occurrence of headache, flushing, dyspepsia, nasal congestion, visual changes, and other side effects.

Results: The adverse reactions most commonly observed were flushing (30.8%), headache (25. 4%), nasal congestion (18.7%), and heartburn (10.5%). All events were short lived and mild in nature. In the present study, 31.6% of patients experienced one or more adverse events. However, no one withdrew from the study because of the severity of these events. There was a significant association between higher doses and the occurrence of side effects.

Conclusions: The incidence of adverse events attributable to sildenafil citrate may be higher than initially reported, but an explanation may be the methodology of data collection and the industry-independent nature of this study. The side-effect profile is dose related and mild. Sildenafil citrate remains a safe and well-tolerated treatment for erectile dysfunction.

MeSH terms

  • Adult
  • Aged
  • Dizziness / chemically induced
  • Dyspepsia / chemically induced
  • Erectile Dysfunction / drug therapy*
  • Flushing / chemically induced
  • Headache / chemically induced
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Nose / drug effects
  • Phosphodiesterase Inhibitors / administration & dosage
  • Phosphodiesterase Inhibitors / adverse effects*
  • Piperazines / administration & dosage
  • Piperazines / adverse effects*
  • Prospective Studies
  • Purines
  • Sildenafil Citrate
  • Sulfones
  • Vision, Ocular / drug effects


  • Phosphodiesterase Inhibitors
  • Piperazines
  • Purines
  • Sulfones
  • Sildenafil Citrate