Americans wanting to buy many common cold medicines would have to go to a drug store and ask the pharmacist under legislation introduced on Wednesday aimed at fighting the spread of the illegal stimulant methamphetamine.

The proposed Senate bill would apply to medicines, such as Sudafed, that contain the decongestant pseudoephedrine - the main ingredient in methamphetamine, or “meth.”

The medicines now sold widely from grocery shelves and elsewhere would have to be stored behind the pharmacy counter and dispensed by a pharmacist or a pharmacy technician, although a prescription would not be needed. Purchasers would have to sign for it and show identification.

The aim is to help fight “crooks and cooks” who buy common cold and sinus pills and turn them into dangerous meth in makeshift labs, Missouri Republican Sen. Jim Talent said. Methamphetamine is a growing problem in states across the country, and doctors do not have good techniques of treating addiction.

Similar efforts to restrict pseudoephedrine sales have failed in the past because big drug makers opposed it, backers of the legislation acknowledged. But this version is modeled on a successful program in Oklahoma and already has significant bipartisan support, they said.

Sen. Dianne Feinstein, a California Democrat and co-sponsor of the bill, said her staff had gone to a local supermarket and purchased many boxes of cold pills “and nobody lifted an eyelid.”

In rural areas where pharmacies are scarce, other outlets could sell the medicines behind the counter.

The legislation limits purchases to nine grams, or about 300 pills, in a 30-day period. That many pills could be turned into about 25 doses of methamphetamine in an illicit lab, an aide to Feinstein said. More than 9,000 such labs were seized by authorities in the United States in 2002, the most recent year statistics are available, the aide said.

The legislation would fund state programs to track pseudoephedrine purchases by computer.