Updated

The nation's shortage of execution drugs is becoming increasingly acute as more compounding pharmacies conclude that supplying the lethal chemicals is not worth the bad publicity and the legal and ethical risks.

The scarcity of drugs for lethal injections has forced states to scramble for substitutes. And experts say that whatever alternatives are found will almost certainly face costly court challenges made more complicated by laws that cloak the process in secrecy.

On Monday, the Tulsa, Okla.-based compounding pharmacy the Apothecary Shoppe agreed to stop selling pentobarbital to the Missouri Department of Corrections after the pharmacy was named in a lawsuit filed by Missouri death row inmate Michael Taylor alleging that the drug could cause "inhumane pain."

Missouri previously paid $8,000 in cash for each dose of the drug.