Nubain Mechanism of Action

Pharmacology: Pharmacokinetics: Nalbuphine HCl is a potent analgesic, 10 mg of which is comparable in analgesic potency to 8-10 mg of morphine sulfate, whether administered IV, SC or IM.
The onset of action occurs within 2-3 min after IV administration of nalbuphine HCl and in <10 min following SC or IM injection.
Clinical experience suggests that in some patients, analgesia may be longer lasting than from comparable doses of morphine, effects having been observed in acute and chronic pain for 3-8 hrs. The half-life (t_½) of nalbuphine is 5 hrs.
Nubain has the effect of lowering the cardiac work load and can be used immediately in myocardial infarction (use with caution where emesis is involved). Hemodynamic studies in patients with severe arteriosclerotic heart changes reveal that nalbuphine HCl has circulatory effects similar to those of morphine ie, a minimal decrease in oxygen consumption, cardiac index, left ventricular end diastolic pressure and cardiac work.
Nubain antagonist activity is ¼ as potent as nalorphine and approximately 1/40 that of naloxone.