The cold medicine industry is battling a new strain of legal headaches involving the unlawful use of pseudoephedrine, a key ingredient in decongestants that’s used to make crystal meth.

In Oklahoma, a wrongful death lawsuit involving the murder of a state trooper killed by a meth cook has been filed against the makers and sellers of pseudoephedrine, alleging that the drug companies long knew the product was being used for methamphetamine but did nothing about it. Green v. Pfizer, No. CJ-05-00115 (Cotton Co., Okla., Dist. Ct.).