US scientists have developed a method for screening Tamiflu in an attempt to foil counterfeiters.

Counterfeiters have targeted Tamiflu, an antiviral flu drug effective against bird flu, due its high cost and demand. Scientists have found fake Tamiflu containing vitamin C instead of the active ingredient, oseltamivir.

The high cost and demand for Tamiflu has made it a target for counterfeiters

Facundo Fernández and colleagues at Georgia Institute of Technology and the US Centers for Disease Control and Prevention, Atlanta, Georgia, used desorption electrospray ionisation mass spectrometry (DESI MS) to help authenticate Tamiflu capsules. They doped the electrospray solvent with crown ethers and studied the competitive complexation of the crown ethers with oseltamivir. They found that by using two different crown ethers with different binding affinities for oseltamivir, they could determine the amount of oseltamivir in the capsules without using an internal standard.

Niklas Lindegardh, head of the Clinical Pharmacology Laboratory at the Mahidol-Oxford Tropical Medicine Research Unit, Bangkok, Thailand, says he believes this is important research. 'Rapid analytical methods for screening potentially counterfeit Tamiflu capsules are of the utmost importance. The new reactive DESI method combines rapid throughput with ultimate selectivity and will provide an excellent tool for rapid semi-quantitative screening of large batches of capsules,' he says.

'The new method improves throughput by at least two orders of magnitude,' says Fernández. 'Even with existing instrumentation, this assay could be widely adopted.' He says the next challenge is to couple the ionisation reaction to portable detectors, such as ion mobility spectrometers or portable mass spectrometers. 'This will truly produce a network of point-of-care drug quality screening tools. The challenge is mostly on the engineering side. The basic knowledge is already there and we have proven the basic chemical concepts,' adds Fernández.

Edward Morgan