Respiratory depression, which is potentially life-threatening and causes substantial morbidity and mortality [11], has been proposed in specific patient populations, such as morbidly obese patients with normal renal function [12] and those with renal impairment and cytochrome P450 family 2 subfamily D member 6 (CYP2D6) gene duplication [13]. This evidence concerns the gene CYP2D6 and Respiratory insufficiency due to muscle weakness.