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Traditionally, opioids have been administered as fixed doses at fixed dose intervals. This approach has been largely ineffective. Patient-controlled analgesia (PCA) and upgraded traditional approaches incorporating flexibility in dose size and dose interval, and titration for an effect in individual patients with the monitoring of pain and sedation scores, can greatly improve the efficacy of opioid administration. Optimising opioid use, therefore, entails optimising the titration process.

Opioids have similar pharmacodynamic properties but have widely different kinetic properties. The most important of these is the delay between the blood concentrations of an opioid and its analgesic or other effects, which probably relate to the delay required for blood and brain and spinal cord (CNS) equilibrium. The half-lives of these delays range from approximately 34 minutes for morphine to 1 minute for alfentanil. The …