The general “Rule of Thumb” for drug administration in elderly folks is “to start low and go slow.” This is no different for opioids. In general, elderly patients have lower analgesic requirements secondary to increased brain sensitivity to opioids with age. According to Miller, sufentanil, alfentanil, remifentanil, and fentanyl are twice as potent in elderly patients. You can effectively halve your bolus dose with all these opioids.
The elderly are also impacted by age-related changes to pharmacokinetics, including decreased volume of the central compartment and decreased clearance. Elderly patients may have associated renal insufficiency that impairs elimination of active metabolites such as morphine-6-glucuronide, which will accumulate in the system leading to prolonged duration of action.
Unique considerations for administering opioids in the elderly also include increased incidence of postoperative delirium. This complication is multifactorial: some argue opioids can exacerbate delirium, but some attribute it to uncontrolled postoperative pain. In any case, a multimodal approach is beneficial with judicious use of opioids, starting with smaller doses and increasing dosing interval.