The House Energy and Commerce Committee has sent letters to Pfizer, GlaxoSmithKline, Eli Lilly, Johnson & Johnson and Serono, requesting the information by mid-February.
In the US, there has been an upsurge in interest in developing ways to safeguard the integrity of the pharmaceutical supply chain in the wake of an upswing in the number of cases of drug counterfeiting. The US Food and Drug Administration (FDA) has set up a taskforce to deal with the problem that is due to deliver its first advice early this year.
"We are interested in any ongoing efforts or plans by your company to prevent counterfeiting and diversion of your drugs, and to prevent any involvement of your products with illicit Internet sites and foreign pharmacies," said the committee in the letters.
The panel is interested in both the technological aspects of anti-counterfeiting, such as bar codes, identification numbers and 'track and trace' measures, as well as a series of new agreements put in place with wholesalers and distributors to prevent diversion of drugs.
Diversion of products into so-called 'secondary markets' overseas provides a route for counterfeit drugs to enter the supply chain, and this is believed to have contributed to a large-scale Lipitor fraud uncovered last year. But this is a thorny issue, with some claiming that the industry is using counterfeiting as an excuse to prevent parallel import of drugs from cheaper countries to those where they are more expensive.
Some of the medicines that are particularly prone to counterfeiting include Pfizer's cholesterol drug Lipitor (atorvastatin) and erectile dysfunction drug Viagra (sildenafil), Johnson & Johnson's red blood cell booster Procrit (epoetin alpha) and GSK's HIV treatments, notably Combivir (zidovudine plus lamivudine).
Serono has been approached because its growth hormone product Serostim (somatropin) is also a favourite of the counterfeiters. A report in 2002, published by Reconnaissance International, suggested that there was a thriving black market for this product among weight-lifters, athletes and perhaps even racehorse owners.