TABLE 2.

Clinical Case Examples¹⁰⁴

Clinical Scenario	Problem	Next Step
Patient is prescribed morphine 15mg PO q4hr PRN and uses 6 doses per day. Each dose reduces pain by 60% and causes no side effect; patient wakes every night to take PRN opioid.	Needs a long-acting opioid	This patient is using a total of 90mg/day of oral morphine. Extended-release morphine is available in 15mg, 30mg, 60mg, 100mg, and 200mg tablets. A clinician could start morphine extended release 45mg PO q12hr (replaces 100% of current daily use but requires prescribing both a 30mg tablet and a 15mg tablet); alternatively, a clinician could start morphine extended release 30mg PO q12hr (replaces 2/3 of current daily use but lower pill burden per day) and then reassess again in 1–2 weeks.
Patient is prescribed oxycodone 5mg PO q6hr PRN and uses all 4 allotted doses per day. Patient reports that each PRN dose reduces pain by 70% but pain relief lasts only 3 hours. By the time the patient is able to take the next PRN dose, the pain has escalated to an intolerable level. Patient has normal renal/hepatic function.	End-dose failure due to inappropriate dosing interval	A patient with normal renal and liver function should have a dosing interval of q4hr for an immediate release opioid. The proper regimen for this patient would be oxycodone 5mg PO q4hr, not q6hr. This patient may need addition of a long-acting opioid, but it would be appropriate to first properly prescribe the PRN regimen and then use the total daily opioid use to calculate an effective dose of an extended-release opioid.
Patient is prescribed morphine extended release 200mg PO q12hr and morphine immediate release 7.5mg PO q4hr PRN. Patient takes 3 PRN doses per day but reports that each PRN reduces pain from a 9/10 to an 8/10.	Inadequate dose of PRN opioid	A typical PRN opioid dose is calculated as approximately 10%-20% of the total daily opioid requirement. Thus, a patient using morphine 200mg PO q12hr (or 400mg/day) should have morphine immediate release PRN of approximately 40mg. Since morphine immediate release does not come in a 40mg tablet, it would be appropriate to start with one tablet of morphine immediate release 30mg and assess response.

Abbreviations: PO, orally; PRN, pro re nata (as needed); q12h, every 12 hours; q4h, every 4 hours; q6h, every 6 hours.

^aSee Goldberg & Smith 2013.¹⁰²