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J R Soc Med. 2002 October; 95(10): 528.
PMCID: PMC1279201

Epistaxis after sildenafil

Ms Hicklin and colleagues (August 2002 JRSM1) describe two cases of epistaxis after use of sildenafil to enhance penile erection. Such a complication is not unexpected, for two reasons. First, the enzyme inhibited by the drug, cyclic guanosine monophosphate-specific phosphodiesterase type 5 (PDE5), is present at several sites other than the corpus cavernosum, and known effects of the consequent vascular smooth muscle relaxation include headache in 16%, facial flushing in 10%, and hypotension and dizziness in 2% of patients2. Second, in-vitro research suggests that sildenafil can inhibit PDE5-induced platelet aggregation3. Cerebrovascular haemorrhage is a recognized, albeit rare, side-effect and bleeding from oesophageal varices4 and from haemorrhoids5 has been described after use of sildenafil.

In case 2 of Hicklin et al. the patient had been prescribed amlodipine. This drug is metabolized by the same enzyme (cytochrome p450) and could therefore affect the pharmacokinetics of sildenafil, rendering haemorrhage more likely.


1. Hicklin LA, Ryan C, Wong DKK, HInton AE. Nose-bleeds after sildenafil (Viagra). J R Soc Med 2002;95: 402-3 [PMC free article] [PubMed]
2. Morales A, Gingell C, Collins M et al. Clinical safety of oral sildenafil citrate (VIAGRA®) in the treatment of erectile dysfunction. Int J Impot Res 1998;10: 69-74 [PubMed]
3. Berkels R, Klotz T, Sticht G, Englemann U, Klaus W. Modulation of human platelet aggregation by the phosphodiesterase type 5 inhibitor sildenafil. J Cardiovasc Pharmacol 2001;37: 413-21 [PubMed]
4. Tzathas C, Christidou A, Ladas SD. Sildenafil (Viagra) is a risk factor for acute variceal bleeding. Am J Gastroenterol 2002;97: 1856 [PubMed]
5. Sheikh AR, Yasmeen S, Prindiville TP. Hemorrhoidal bleeding associated with sildenafil. Am J Gastroenterol 2001;96: 2518-19 [PubMed]

Articles from Journal of the Royal Society of Medicine are provided here courtesy of Royal Society of Medicine Press