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Analgesic efficacy. This graph illustrates a typical dose-response curve for orally administered (PO) analgesics. The dose-response curve for opioids such as morphine demonstrates unlimited efficacy in which greater doses provide greater analgesia. At equipotent doses, all opioids demonstrate a similar dose response. In contrast, nonopioids demonstrate a “ceiling” effect that generally is adequate for relief of mild to moderate pain (pain relief rating of 4–5 in this scale). For ibuprofen, doses greater than 400 mg do not provide further analgesia. For aspirin (ASA) and acetaminophen (APAP), this ceiling effect is achieved at 1000 mg and is somewhat lower than that provided by nonsteroidal anti-inflammatory drugs (NSAIDs).

Molecular structures of morphine, codeine, and derivatives. The top row illustrates molecular structures for morphine and its two derivatives, hydromorphone and oxymorphone. The subtle changes indicated by the asterisks enhance affinity for the opioid receptors, which accounts for greater potency. The bottom row illustrates codeine and its derivatives, which differ from their morphine-derived counterparts only in a methyl substitution (circled). Approximately 60% of an oral dose of codeine-related products is absorbed and may be subjected to varying degrees of demethylation by CYP2D6 to its active metabolite. Framed molecules are those credited with the analgesic effect provided by various codeine-related products. Codeine has little affinity for opioid receptors. Roughly 10% of an absorbed dose is demethylated to morphine, which is credited with its analgesic effect. Hydrocodone and oxycodone have good receptor affinity and provide an analgesic effect. The analgesic effect of hydrocodone is credited to both the parent drug and its active metabolite, hydromorphone, but analgesia provided by oxycodone is almost entirely the result of the parent drug. Very little is demethylated to oxymorphone.

Relationships between analgesic efficacy of fentanyl (%MPE) and A118G genotypes.

Frequency of need for postoperative analgesics following sagittal split mandibular osteotomy (SSMO) compared with that following oral soft tissue surgery.

Analgesic Doses Taken During the First 72 Hours Postoperatively in Opioid-Using and Opioid-Naïve Patients.

Patients with chronic pain on opioid therapy used more analgesics (mean, SD) during the first 72 hours postoperatively vs opioid-naïve patients without chronic pain.