The pharmaceutical industry is helping state law enforcement officers track sales of a popular over-the-counter decongestant as part of a crackdown on "smurfing," a way of collecting a key ingredient in the illegal drug methamphetamine.

Authorities hope the industry-funded tracking system will tip the advantage in their favor in a long-running battle with meth cooks.

Pharmaceutical companies have been pushing to expand the tracking system amid growing calls to require prescriptions for pseudoephedrine, the legal decongestant that is also used to make meth.

South Carolina is among 10 states that have passed laws adopting NPLEx, the industry's system to track pseudoephedrine. Two states have begun requiring prescriptions for the drug, often marketed as cold and allergy medicine.

The decongestant remains available without a prescription in S.C., although retailers must keep it behind the counter.

Pharmacies statewide have been recording who is buying the drug and how much since 2006, but they had no means of sharing the information with each other until recently.

NPLEx, or National Precursor Log Exchange, puts all the purchases in one database, making it easier to track sales at different pharmacies. When a customer tries to buy more than the limit, retailers receive a recommendation to deny the sale, as a message is sent to the State Law Enforcement Division.

Sales of more than 6,000 boxes of pseudoephedrine have been blocked since the system went live in the state on Jan. 1, according to SLED records.

"Every single time a product gets blocked, you could be preventing a meth lab from happening," said Mandy Hagan, the director of state government relations for the Consumer Healthcare Products Association, the group leading the NPLEx lobbying effort.

Privacy Rights Clearinghouse and the Electronic Privacy Information Center said they aren't watching NPLEx but that the system raises general concerns about privacy of medical records.

"When personal information is collected into a database, there is always a chance of some secondary use," said Tena Friery, research director for the San Diego-based clearinghouse.

Federal law makes clear that information gathered by NPLEx is accessible to law enforcement only, Hagan said.

Kentucky, the state that pioneered the system, is blocking the sale of 10,000 grams of pseudoephedrine per month -- enough to make 5,000 grams of meth, Hagan said. Meth lab incidents in S.C. fell from 199 to 26 from 2004 to 2007 and then began climbing back up, reaching 77 in 2009, the last year for which data is available, according to the Drug Enforcement Administration.

Each lab costs an average of $2,200 to clean up and is often full of toxic chemicals that can sicken officers or explode, according to an audit by the U.S. Department of Justice's inspector general.

The state law that brought the tracking system to S.C. also lowered the caps on purchases of pseudoephedrine to 3.6 grams per day and 9 grams every 30 days. Ephedrine and phenylpropanolamine are also subject to the limits.

Customers who buy or possess more than the limit face up to five years in prison and a $5,000 fine for a first offense under the new law. Multiple offenses could result in a 10-year prison sentence or a minimum fine of $10,000.

Dr. Emmanuel Sarmiento of the Allergic Disease and Asthma Center in Greenville said it is rare for patients to need more than 240 milligrams a day.

Patients who do need more can get a letter from a doctor exempting them from state limits, he said. Taking high doses of pseudoephedrine for a sustained period can lead to heart arrhythmia and prostate problems, he said.

Oregon and Mississippi are the only states that require a prescription for pseudoephedrine. State Sen. Mike Fair, R-Greenville, said S.C.'s meth problem left the state with the choice between the tracking system and requiring prescriptions. Only if NPLEx turns out to be an "abject failure" does he expect lawmakers to revisit the prescription idea.

Walgreens, CVS, Rite Aid and Wal-Mart are among the retailers using NPLEx, according to SLED.

Retailers face up to three years in prison and $10,000 in fines for violating the law.

Purchases follow customers over state lines. North Carolina doesn't use the tracking system, and Georgia lawmakers are considering it, Hagan said.