The prolonged execution of an Arizona death row inmate with a new, two-drug combo has highlighted the patchwork quilt approach that states now take with lethal drugs, with types, combinations and dosages varying widely. Oklahoma has authorized five different lethal injection protocols: a three-drug method beginning with sodium thiopental, pentobarbital, or midazolam, a two-drug procedure using midazolam and hydromorphone, or a single, lethal dose of pentobarbital. [...] supplies of the drugs started to run short as death penalty opponents in Europe put pressure on their drugmakers — which manufactured key anesthetics — to prohibit their use in executions. [...] states eager to avoid ongoing lawsuits alleging the old three-drug method caused inmates to suffer unconstitutional levels of pain looked for alternatives beginning about five years ago. The compounded version is difficult to come by, with most compounding pharmacists reluctant to expose themselves to possible harassment by death penalty opponents. Many death penalty experts, even some opponents, believe the quickest and most humane method is the firing squad.