In an effort to prevent counterfeiting, Pfizer said it has started to ship Viagra bottles in the U.S. that feature radio chips under the labels. Pharmacists with the proper equipment can read the chip and check the electronic product code stored on it in order to ensure that the product is genuine.

Viagra, a prescription drug used to treat impotence, is one of the most counterfeited medicines in the U.S., said Pfizer. The high cost of the pills has spurred countless unofficial sales channels, many online, with dubious sources for the drug.

Bottles of Viagra will continue to feature barcodes with the same electronic product code. But the RFID (radio frequency identification) tags are difficult and expensive to duplicate so they add another layer of security, Pfizer said.

In order to take advantage of the extra layer of security, pharmacies will need to invest in RFID readers, which pick up the radio transmission from the RFID chip. The readers then communicate with Pfizer servers to verify the product code.

In 2004, the Food and Drug Administration in the U.S. began promoting the use of RFID to cut down on counterfeit drugs and issued general guidelines on using RFID in the supply chain. In late 2004, Pfizer said it would begin planning an RFID program with Viagra with the goal of launching the program in late 2005.

Pfizer said it has invested several million dollars on the RFID project for Viagra. The application is not yet capable of tracking and tracing the pills throughout the supply chain, a capability that would require additional investments. Pfizer is exploring the possibility of implementing track and trace support in the future.

Privacy advocates have cited concerns over the use of RFID in the supply chain for fear that the chips can track consumers' buying habits or transmit other personal information. Pfizer said that their chips are unlikely to travel home with consumers, though. Pharmacists typically dispense Viagra pills in quantities smaller than the amount that comes in a bottle from Pfizer, so it would be rare for a customer to end up with a bottle of Viagra with the RFID chip, Pfizer said.

Another pharmaceutical company, Purdue Pharma LP, began attaching RFID chips to bottles of the painkiller OxyContin in 2004 in an effort to cut down on theft of the pills throughout the distribution cycle. Purdue equipped law enforcement officials with RFID readers so they could help track stolen bottles of the drug.

The use of RFID in the supply chain is being driven in the U.S. by retailer Wal-Mart Stores, which has issued a mandate to its biggest suppliers that they must implement an RFID program in order to continue to do business with the retailer.