Which receptor does Butorphanol primarily act on?

Butorphanol primarily acts on the kappa opioid receptor, which is a key aspect of its pharmacological profile. Kappa receptors play a significant role in mediating analgesic effects, particularly in the context of pain relief, and they contribute to the drug's ability to provide effective analgesia. Activation of kappa receptors also tends to result in fewer side effects commonly associated with mu receptor activation, such as respiratory depression and addiction potential, making butorphanol a useful option in certain clinical scenarios.

Additionally, while butorphanol does have some activity at mu receptors, its kappa receptor agonism is predominant, which differentiates it from other opioid analgesics that primarily target mu receptors. This selective action can lead to a ceiling effect on analgesia and a lower risk of side effects.

The other receptors listed, including the delta opioid receptor and alpha-2 adrenergic receptor, are less relevant to butorphanol’s primary action. Delta receptors are more associated with the modulation of emotional responses to pain rather than direct analgesic effects, and while alpha-2 adrenergic receptors are involved in pain modulation, butorphanol is not primarily known for activity on these receptors.