Final answer:
Fentanyl has a rapid onset and shorter duration compared to morphine due to its chemical structure and pharmacokinetic properties.
Step-by-step explanation:
Fentanyl has a rapid onset and shorter duration compared to morphine due to its chemical structure and pharmacokinetic properties. Fentanyl is a synthetic opioid that is more lipophilic, meaning it has a higher affinity for fat molecules. This allows it to rapidly cross the blood-brain barrier and bind to opioid receptors in the brain, resulting in quick onset of analgesic effects. Additionally, fentanyl is metabolized more quickly than morphine, leading to a shorter duration of action.