Pharmacology of oral combination analgesics: rational therapy for pain.

No single analgesic agent is perfect and no single analgesic can treat all types of pain. Yet each agent has distinct advantages and disadvantages compared to the others. Hence, clinical outcomes might be improved under certain conditions with the use of a combination of analgesics, rather than reliance on a single agent. A combination is most effective when the individual agents act through different analgesic mechanisms and act synergistically. By activating multiple pain-inhibitory pathways, combination analgesics can provide more effective pain relief for a broader spectrum of pain, and might also reduce adverse drug reactions. This overview highlights the therapeutic potential of combining analgesic medications with different mechanisms of action, particularly a nonsteroidal anti-inflammatory drug (NSAID) or acetaminophen with an opioid or tramadol.