Washington ? An association representing more than 36,000 pharmacies is issuing guidelines for possible federal legislation to restrict sales of cold medications containing a substance often used in the illegal manufacture of methamphetamine — or “speed.”

Pseudoephedrine, a main ingredient in a number of over-the-counter drugs like Sudafed, Nyquil and Sinutab, can be extracted by boiling down the cold medicines; toxic chemicals are then used to turn the substance into highly concentrated meth.

The National Association of Chain Drug Stores, moving to avoid a hodgepodge of state laws, is calling for an overarching federal law that would require that such products be kept behind the pharmacy counter and sold only by a licensed pharmacist or pharmacy personnel.

Purchases should be limited to 9 grams — or 366 30-milligram pills — in 30 days, the association says.

The guidelines also suggest that drugstores be required to keep written or electronic logs of all pseudoephedrine purchases to assist law enforcement efforts.