Management of Severe Pain

Opioid therapy is the cornerstone of management of patients presenting with severe pain. Our practice is to begin with reassurance of patients and their families. We tell them that to relieve the pain as quickly as possible, we will initiate the use of intravenous opioid medications immediately but that we will begin oral pain medication as soon as the pain is well controlled. Without this explanation, patients have misinterpreted a “morphine drip” as an indication that they were considered terminal.

The starting dose is calculated from the patient’s current opioid dose (10% of their 24-hour opioid requirement) or weight (e.g., 0.05 mg/kg/hr of morphine). After the opioid bolus dose is administered, the patient should be monitored continuously during dose titration. If the patient was on standing opioid medication, the medication is continued when possible or converted to a continuous infusion if necessary. Pain is reassessed 20 minutes after the patient receives a bolus dose. If the pain remains severe (7, 8, or 9 of 10), a subsequent bolus dose is administered at double the dose. If the pain has decreased to moderate (4, 5, or 6), another bolus at the same dose as the immediately previous dose is used. If the pain score is below 4, the patient is carefully monitored. At 4 to 8 hours, either a continuous infusion is begun or the ongoing infusion rate is adjusted upward based on the amount of opioid taken as boluses during that period. There is no maximal opioid dose; we give whatever is required to relieve the pain. If the patient falls asleep, this is usually an indication that pain relief has been achieved, not that the dose should be lowered. We lower the dose if the respiratory rate falls to below 10 to 12 breaths/min or if there are signs or symptoms of neurotoxicity (e.g., myoclonus).

Agents to prevent side effects are begun along with the opioid. All patients are given a stool softener and an irritant agent such as senna (one or two tablets orally daily to twice daily, up to a maximum of 8 pills per day). If a more laxative effect is needed, lactulose (15-30 mL) or polyethylene glycol (17 g) is added. In opioid-naive patients, prochlorperazine (Compazine 10 mg taken orally two or three times daily) is ordered as needed to treat nausea. In patients with bone or nerve pain, appropriate adjuvants are added.

When pain relief is adequate, the patient is converted to an equivalent dose of oral or transdermal opioid. If morphine is used, for example, the patient will need three times the parenteral dose that was effective. For example, a patient who requires 10 mg of morphine per hour (i.e., 240 mg/24 hours given intravenously) will need 720 mg/day of the oral sustained-release agent (240 mg every 8 hours). This can also be given orally as 360 mg every 12 hours. Two hours after the long-acting oral opioid is begun, the drip is discontinued. Short-acting immediate-release morphine should be available for rescue dosing at 10% of the total daily dose. For this patient, 60 to 90 mg every 3 to 4 hours is recommended. If the amount of opioid taken as a rescue dose is significant (>25% of the daily dose) for 1 or 2 days, the total dose of long-acting agent is adjusted upward accordingly.

Choice of Medication

Because a wide variety of medications are available, pharmacokinetic considerations and side effect profiles should be considered when choosing opioid agents. Intermittent moderate to severe pain lasting hours to several days is amenable to oral analgesics with short half-lives (3-4 hours) with appropriate potency (e.g., immediate-release oxycodone, morphine, hydromorphone [Dilaudid], or oxymorphone [Opana] when available). Severe pain of relatively constant intensity should be treated with oral sustained-release morphine or oxycodone taken every 8 or 12 hours,^1,2 hydromorphone (Exalgo) taken every 24 hours or oxymorphone (Opana ER) taken every 12 hours, methadone taken every 8 hours, or transdermal fentanyl renewed every 48 to 72 hours. Twelve- to 24-hour formulations of oral morphine (e.g., Kadian, Avinza) are available; for patients unable to take pills, the capsule can be opened and the pellets sprinkled on food or suspended in water and given through a feeding tube¹⁰.

Relative Potencies of Commonly Used Opioids

Conversions Between the Transdermal Fentanyl Patch and Morphine

Emetic Risks of Chemotherapy

Combination Antiemetic Regimens