Nalbuphine
Nalbuphine. Mixed κ-opioid agonist + μ-opioid antagonist — same ceiling effect as pentazocine. Used in obstetric analgesia (less… Subcutaneous half-life 2.3 h.
Mixed κ-opioid agonist + μ-opioid antagonist — same ceiling effect as pentazocine. Used in obstetric analgesia (less neonatal respiratory depression than pure agonists) + procedural pain. Not a controlled substance in the US.
PK: FOUR SEPARATE CROSS-ARM AVERAGES IN ONE RECORD. V 282 L is the mean of two dose arms stated separately (290 and 274); intramuscular F 0.82 is the mean of 81 and 83; the 2.4 h half-lives are the midpoint of a stated "ranged between 2.2 and 2.6 h"; and subcutaneous F 0.78 is neither of the stated 79 and 76 nor even their mean. Each is now the single stated 10 mg arm value, and one disposition half-life of 2.3 h is shared, which the paper itself licenses: the values held "regardless of dose given or route administered", and intramuscular and subcutaneous dosing "appear to be interchangeable". ka 1 is dropped as unsourced AND as quantitatively incompatible with the stated peak at 30 to 40 minutes, which it would place near 1.7 h. DESIGN CAVEAT NOT PREVIOUSLY RECORDED: the study used THREE PARALLEL GROUPS of twelve, not a crossover, so its bioavailability figures are between-group ratios. Oral half-lives of 6.9-7.7 h exist in the literature and are formulation-specific through enterohepatic recirculation; they must never be mixed into these parenteral rows. Two references are removed as a receptor-autoradiography study and a medicinal-chemistry synthesis paper, neither containing pharmacokinetics.
Pharmacokinetics
- IV — t½ 2.3 h · F 100% · Vd 290 L
- Intramuscular — t½ 2.3 h · F 81% · Vd 290 L
- Subcutaneous — t½ 2.3 h · F 79% · Vd 290 L
Sources: PMID:18467078, PMID:3691617, PMID:3429694