The research aimed to study how different opioid pain medications affect the movement of human sperm. They mixed sperm with various opioids like fentanyl and naloxone in a lab setting to see how it changed sperm movement. Findings show that fentanyl, alfentanil, and sufentaril reduced sperm movement by acting on specific receptors, while butorphanol and dezocine affected sperm differently. Naloxone lessened the effect of some opioids on sperm movement. Higher concentrations of certain opioids completely stopped sperm movement. Overall, some opioids can reduce sperm movement by interacting with specific receptors, while others may use different pathways. Additionally, one opioid, pentazocine, was found to increase sperm movement.