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Letters Rogue online pharmacy

Success of rogue online pharmacies: sewage study of sildenafil in the Netherlands

BMJ 2014; 349 doi: (Published 02 July 2014) Cite this as: BMJ 2014;349:g4317
  1. Bastiaan J Venhuis, senior scientific officer1,
  2. Pim de Voogt, professor of environmental chemistry2,
  3. Erik Emke, scientific researcher2,
  4. Ana Causanilles, PhD student2,
  5. Peter H J Keizers, scientific officer1
  1. 1National Institute for Public Health and the Environment RIVM, PO Box 1, 3720 BA Bilthoven, Netherlands
  2. 2KWR Watercycle Research Institute, PO Box 1072, 3430 BB, Nieuwegein, Netherlands
  1. bastiaan.venhuis{at}

The internet continues to harbour thousands of rogue online pharmacies.1 We investigated the success of their practice by measuring the sewage load of the erectile dysfunction drug sildenafil in three cities in the Netherlands.

We measured concentrations of sildenafil and two metabolites at the three main sewage treatment plants serving Amsterdam, Eindhoven, and Utrecht for seven consecutive days.2 Total sewage load was back calculated to original sildenafil consumption.3 For a conservative estimate, we assumed that there were no losses in sewage due to degradation.4 We found no indication of dumping of unused drugs.

We estimated the consumption of legitimately dispensed sildenafil from the national dispensary database from 12 months before the study to three months after. We used the repetitive dispensing behaviour for each patient in the sampled area to estimate consumption during the seven days of sampling. About a quarter of the dispensed sildenafil was prescribed to treat pulmonary hypertension.

The figure shows that at least 60% of the sewage loads of sildenfil were not explained by legitimately prescribed sildenafil. The illicit fraction was similar for each city, despite major differences in tourism and commuting.


Estimated sildenafil consumption in three cities in the Netherlands by type of prescription (illicit and dispensed)

We conclude that the unexplained fraction of sildenafil in sewage is primarily illicit. If our results are representative of other communities, the consumption of illicit erectile dysfunction drugs might dwarf the consumption of the legitimately dispensed versions. The apparent success of rogue online pharmacies would be an important area of further inquiry.


Cite this as: BMJ 2014;349:g4317


  • Competing interest: None declared.

  • Pim de Voogt is also professor of environmental chemistry at the Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands.

  • Full response at:


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