Which opioid agonist does not act on delta and kappa receptors?

Remifentanil is an opioid agonist that is specifically designed to act primarily on the mu opioid receptors without significant activity on the delta and kappa receptors. This characteristic is crucial for its clinical use, as it allows for effective pain relief with a rapid onset and a short duration of action, making it ideal for procedures requiring quick recovery from anesthesia. Remifentanil is metabolized quickly by plasma esterases, leading to a very predictable and controllable effect, which is particularly useful in surgical settings.

The other options mentioned have varying degrees of action on delta and kappa receptors, which can influence their therapeutic effects and side effect profiles, but Remifentanil stands out for its selective action.