Pharmacologic Pain Management
Principles
Treat pain with a mechanism-informed, multimodal plan and reassess benefit and harm. Nonopioid foundations include acetaminophen and NSAIDs when not contraindicated, topical agents for localized pain, and selected adjuvants such as gabapentinoids, SNRIs, or TCAs for neuropathic pain. Opioids can be appropriate for severe acute pain or selected chronic cancer or noncancer pain, but start low, titrate to function, and monitor.
Opioid safety
Before starting, assess risk, check the prescription drug monitoring program, discuss goals and adverse effects, and consider a written agreement. Constipation is predictable; prescribe a bowel regimen. Sedation and respiratory depression are dose-related and increased by benzodiazepines, alcohol, and renal or hepatic impairment. Tolerance is needing more for the same effect; physical dependence is withdrawal on abrupt stop; opioid-induced hyperalgesia is worsening pain with escalating dose; addiction is compulsive use despite harm. These are distinct.
Traps
Questions often test equianalgesia and incomplete cross-tolerance. When rotating opioids, reduce the calculated equianalgesic dose, often by 25-50%, then titrate. Avoid meperidine for chronic pain because of neurotoxic metabolites. Tramadol lowers seizure threshold and can cause serotonin syndrome. Do not add a second long-acting opioid or combine benzodiazepines casually.
Worked example
A patient on morphine 60 mg/day has poorly controlled cancer pain and sedation. Calculate the equianalgesic dose, reduce for incomplete cross-tolerance, and reassess frequently. Rule of thumb: the right dose is the lowest one that improves function with acceptable adverse effects, not the dose that makes the number zero.