FAST ONSET OF ACTION IS IMPORTANT IN OPTIMAL TREATMENT OF ACUTE POST-OPERATIVE PAIN
Pharmacokinetics and pharmacodynamics are key to offering optimal treatment of acute post-operative pain.1 To best match the post-operative pain profile, analgesia should be immediate release, have a rapid onset and a short duration of action.1 The onset of pain relief is dependent on different parameters, e.g.:
- Plasma uptake: this varies considerably depending on the method of administration and the properties of the formulation. It is important to know how both impact on plasma uptake.2
- Blood-brain equilibration: some commonly-used opioids have slow blood-brain equilibration times.3,4 This is dependent on the lipophilicity of the drug molecule – lipophilic molecules cross the blood-brain barrier more quickly.
1 de Leon-Casasola O et al. A review of the literature on multiple factors involved in postoperative pain course and duration. Postgrad Med. 2014; 126: 42-52.
2 Hoskin PJ et al. The bioavailability and pharmacokinetics of morphine after intravenous, oral and buccal administration in healthy volunteers. Br J Clin Pharmac. 1989; 27: 499-505.
3 Lötsch J et al. The transfer half-life of morphine-6-glucuronide from plasma to effect site assessed by pupil size measurement in healthy volunteers. Anesthesiology. 2001; 95: 1329-38.
4 Schafer SL, Flood P. The pharmacology of opioids. In Geriatric Anesthesiology. New York, NY: Springer Verlag. 2007: Ch. 15, Table 15-1.