Circadian rhythms in opioid-induced hyperalgesia: call for comprehensive research. Comment on Br J Anaesth 2023; 131: 1072–81

Editor—We read with interest the study by Shu and colleagues,1 which convincingly demonstrates that opioid-induced hyperalgesia (OIH) is subject to circadian variations. Although the study highlights the potential involvement of metabolic enzyme rhythms in OIH, we would like to highlight several issues that require further clarification.