Lethality due to tramadol alone however, requires ingestion of at least 100 times the therapeutic 50 mg dose (i.e., 100 standard 50 mg tablets), and effects of its intoxication reflect more its monoaminergic activity and seizures, rather than MOR agonist-induced respiratory depression (De Decker et al., 2008; Shadnia et al., 2008; De Backer et al., 2010). Here, OPRM1 is linked to respiratory depression.