Half of Tamiflu prescriptions went unused during 2009 H1N1 swine flu pandemic, sewage study concludes

Press release 2013/03 – Issued  by the  Centre for Ecology & Hydrology, UK

 

A new study concludes that  approximately half of the prescriptions of Tamiflu during the 2009-10 influenza  pandemic went unused in England. The unused medication represents approximately  600,000 courses of Tamiflu at a cost of around £7.8 million to the UK taxpayer.  The novel scientific method used in the study could help measure and improve  the effectiveness of future pandemic flu strategies.

The finding, published online in  the open access scientific journal PLOS ONE, comes from the first study of its  kind to use sewage water to estimate drug compliance rates, the degree to which  a patient correctly follows medical advice to take medication. The study  estimated usage of pharmaceuticals from large populations by sampling sewage  and recovering the active component of Tamiflu thus measuring drugs that were  actually consumed by patients, rather than those that were flushed away without  being consumed.

The work was led by scientists at  the UK’s Centre for Ecology & Hydrology working with colleagues at Uppsala,  Linnaeus and Umeå Universities, Sweden, and the  University of South Bohemia, Czech Republic.

Lead author Dr Andrew Singer, a  Chemical Ecologist from the Centre for Ecology & Hydrology, says,  “Influenza pandemics are rare, making a study such as this a unique and  important window into how people behave during a public health emergency such  as a pandemic. This study sheds new light on people’s willingness to follow  medical advice on antiviral usage. Importantly, this method could be used to  monitor how many people take certain kinds of medicine in real time and alert  national health authorities to the need for stronger public information  campaigns during pandemic emergencies.”

The research highlights that  despite the central role of antivirals in many nations’ influenza pandemic  preparedness plans, there remains considerable uncertainty regarding antiviral  compliance rates. Poor compliance drains resources by diverting limited  antiviral stocks from those who may need it most. Mis-used antivirals can lead  to antiviral resistance and represents a significant financial cost and health  risk. Previous research on antiviral compliance had focused on small  populations, typically fewer than 200, and used survey-based analyses of drug  compliance, which can be unreliable.

Dr Singer adds, “Our study was the  first compliance study to utilise waste water as an evidence base for whether a  population consumed Tamiflu or not. Because of this unique study design, we  were able to examine populations orders of magnitude larger than previous  studies. One population was just over 6,000 people and the second population  was 208,000. Tamiflu gets transformed into the active antiviral only after  being consumed, and is released into the sewage with every visit to the toilet.  This waste water epidemiology approach is particularly robust for drugs such as  Tamiflu and potentially more reliable than some survey based methods of  assessing compliance.”

Predictions of oseltamivir  consumption from Tamiflu recovered in sewage were compared with two sources of  national government statistics to derive compliance rates. Scenario and  sensitivity analysis indicated an estimated compliance rate between 45-60%,  (between 45 to 60 people out of every 100 people who received Tamiflu completed  the antiviral course, as prescribed).

Dr Singer says, “With  approximately half the collected antivirals going unused, there is a clear need  to improve public health messages so that less antiviral is wasted and that the  duration and severity of infection is reduced. Furthermore, we feel the waste  water epidemiology approach undertaken can potentially help shape future public  health messages, making them more timely, targeted, and population sensitive,  while potentially leading to less mis- and un-used antiviral, less wastage and  ultimately a more robust and efficacious pandemic preparedness strategy.”

Notes to Editors

For further information, or to request interviews with Dr Andrew Singer, please contact the CEH press office.

This research was supported by the  Swedish Research Council Formas, the Natural Environment Research  Council–Knowledge Transfer (PREPARE) Initiative contract NE/F009216/1 to  A.C.S., and the Ministry of Education, Youth and Sports of the Czech Republic  CENAKVA No. CZ.1.05/2.1.00/01.0024 and the Grant Agency of the University of  South Bohemia No. 047/2010/Z to R.G. and G.F.F. Hoffman – La Roche Ltd. donated  deuterated OC.

Full paper reference: Andrew C.  Singer, Josef D. Järhult, Roman Grabic, Ghazanfar A. Khan, Ganna Fedorova,  Jerker Fick, Richard H. Lindberg, Michael J. Bowes, Björn Olsen and Hanna  Söderström. ‘Compliance to oseltamivir among two populations in Oxfordshire,  United Kingdom affected by influenza A(H1N1)pdm09, November 2009 – a waste  water epidemiology study’ is published in PLOS ONE. The paper will be available from: http://dx.plos.org/10.1371/journal.pone.0060221.

Staff page of Dr Andrew Singer