Pre-emptive analgesia and protective premedication. What is the difference?

The management of postoperative pain has been greatly informed by an increasing understanding of the basic science of pain transmission. The idea that analgesia given before the injury would be more effective than the same analgesia given after the injury was named pre-emptive analgesia. The evidence for this phenomenon in postoperative pain management has been very mixed. The methodological problems of such studies, and the difficulties of all the major outcome measures make comparison of the studies available difficult. In the 20 years since the concept was proposed there has been a change in anaesthetic practice that in effect incorporates pre-emptive analgesia with opiates. Evidence for any pre-emptive analgesic with non-steroidal anti-inflammatory drugs is very poor, but the use of local anaesthetic blocks continues to be an area of study. Pre-emptive use of analgesic drugs is not the magic bullet to prevent postoperative pain, but is a strategy of use, among others for managing postoperative pain. Protective analgesia is a strategy that has grown out of the same desire to give drugs before injury to reduce the pain experienced afterwards. In this case the drugs under study have not been primary analgesics, but adjuvant drugs used commonly in the non-acute pain arena. In particular, the drug gabapentin, and to a lesser extent its related drug pregabalin. These drugs have been given by mouth as a pre-medicant, 1 hour before surgery in a variety of operations. A recent meta-analysis of the existing literature shows reduction of postoperative morphine consumption but little reduction in reporting of opiate side effects. Pregabalin, which has a better pharmacokinetic profile, may be a better alternative, and is currently under study. Neither gabapentin nor pregabalin are licensed for use in postoperative pain, and it is unlike that the manufacturers will seek such a licence.