Analogues of erectile dysfunction drugs: an under-recognised threat.

OBJECTIVES To investigate the problem of drug analogue adulteration in male erectile dysfunction health products. DESIGN Survey of over-the-counter male erectile dysfunction health products available in convenience stores and pharmacies in Hong Kong. SETTING Tertiary referral centre for clinical toxicology analysis in Hong Kong. MAIN OUTCOME MEASURES The pattern and extent of adulteration of male erectile dysfunction health products with sildenafil, tadalafil, and vardenafil as well as their structurally modified analogues. RESULTS Of 26 products studied, one (4%) was found to contain undeclared sildenafil, while 14 (54%) contained drug analogues of different kinds. The latter included acetildenafil, hydroxyacetildenafil, hydroxyhomosildenafil, and piperidenafil. The first three were analogues of sildenafil and the last was an analogue of vardenafil. One young patient presented with ataxia after taking an acetildenafil-containing product. CONCLUSIONS The positive rate of concealed drug analogues in male erectile dysfunction health products is alarmingly high. Such analogues are difficult to detect by ordinary laboratory methods, and might be used in an attempt to evade regulatory inspection. Without going through the stringent drug testing process, the adverse effects of these chemicals remain largely unknown and unpredictable. Effective surveillance system and control measures are needed urgently. The medical profession and the public should be alerted to this under-recognised threat.