This patient with acute severe pain should be treated with hydromorphone. The opioid analgesic hydromorphone is a very effective pain medication. It is preferred over morphine in the setting of kidney failure because it is metabolized primarily by the liver and is less likely to lead to the accumulation of potentially toxic metabolites. When a parenteral route of medication administration is indicated, such as when titrating medication for acute pain, either intravenous or subcutaneous routes are acceptable. The intravenous route results in a faster onset of action, although the medication wears off faster; the subcutaneous route has only a slightly slower onset of action, but the effect may last longer. Absorption and effect are very reliable with both routes of administration. Although the intravenous route tends to be more commonly used, subcutaneous administration is a reasonable alternative in hospitalized patients who may not be good candidates for intravenous medications or may not wish intravenous access, as may occur in patients receiving comfort care measures.

Fentanyl transdermal patches should only be used in patients who already have some degree of opioid tolerance, and this patient is opioid naïve. Additionally, the onset of action for a fentanyl patch is 12 to 18 hours, far too long for a patient with acute severe pain.

Morphine is contraindicated in the setting of significant kidney failure (estimated glomerular filtration rate <30 mL/min/1.73 m²), even at the end of life, due to the accumulation of toxic metabolites that may cause neurotoxicity with symptoms of delirium, myoclonus, and seizure.

This patient has no bowel sounds on examination, and it is unclear whether she would absorb oral medication, such as tramadol. Additionally, oral medications have a longer onset of action than either intravenous or subcutaneous routes. In the setting of acute severe pain, a parenteral route with more reliable absorption and shorter onset of action is more appropriate.