Acute Pain The Dental Pain Model

There are a number of situations in which patients experience acute pain. The post third molar extraction dental pain model is a useful model for the study of analgesia of acute pain. As described by Averbuch and Katzper [44], the model is relatively easy to study and there are few confounding factors. The dental pain studies are conducted in subjects scheduled to have their third molars removed. To be included in analysis, the subjects must experience moderate to severe pain following the extraction procedure. The study drug is administered after the pain assessment. Subjects can receive a local anesthetic, intravenous sedative agents, or antianxiety agents during the surgery; however, subjects cannot receive any analgesic for 24 hours prior to study. The efficacy endpoints include pain intensity score measured by a 4-point categorical scale (from 0=none to 3=severe) and pain relief score measured by a 5-point categorical scale (from 0=no relief to 4=complete relief). The scores are determined beginning just prior to drug administration and at various times until six hours postdose. Rescue analgesia medication is allowed, but subjects are excluded from further pain measurements afterwards. A measure of efficacy is the pain intensity difference (PID). The PID is calculated by subtracting the pain intensity at a specific assessment time from the baseline score. Positive values indicate a lessening of the patient's pain, while a negative value indicates increasing pain. One problem pointed out by Averbuch and Katzper is that patients who begin with severe pain can achieve a greater reduction in pain than patients who begin with moderate pain. One can stratify patients by baseline pain severity for statistical analysis. Investigators can use the dental pain model to compare two or more different drugs, to compare a new dug to placebo, or to evaluate several different doses of one drug. Although the dental pain model is simple and well defined, it is not clear how well the model represents all acute pain situations.

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