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 Patient control of pain medication after surgery reduces pain but increases use of morphine

McNicol ED, Ferguson MC, Hudcova J Patient controlled opioid analgesia versus non-patient controlled opioid analgesia for postoperative pain. Cochrane Database Syst Rev. 2015;6:CD003348.

Review question

In people who have just had surgery, is patient-controlled pain medication effective and safe?


Pain after surgery is often managed by intravenous (IV) medications such as morphine. Often, patients have to ask a nurse for their pain medications or wait until the medication has been scheduled. It has become more common, however, for patients to be able to control their own IV pain medicine, within limits set by their doctors, by pressing a button that operates a pump connected to the IV.

How the review was done

The researchers did a systematic review based on studies available up to January 2015.

They found 49 randomized controlled trials (3,412 people, age range 7 years to adulthood) that compared patient-controlled pain medication with pain medication given by medical staff (e.g., through the IV, by needle, or as pills). People in the patient-controlled group did not receive any pain medication given by medical staff.

What the researchers found

The quality of evidence varied. The following results on pain and morphine use are based on moderate-strength evidence.

Compared with pain medication given by medical staff, patient-controlled pain medication:

  • reduced pain in the first 24 hours after surgery; and
  • increased the amount of morphine used from 25 to 48 hours after surgery.

Groups did not differ for serious adverse events, sedation (calming effects), nausea and/or vomiting, itching, slow breathing, or difficulty emptying the bladder.


Patient control of pain medication reduces pain on the day after surgery but increases use of morphine during the second day after surgery compared with pain medication given by medical staff.

Patient-controlled pain medication vs pain medication given by medical staff after surgery*


Number of studies (number of people)

Effects of patient control of pain medication

Pain in the first 24 hours after surgery (on a scale of 0 to 100)

23 studies (1516 people)

9-point reduction in pain with patient-control of pain medication (reduction could be as little as 5 points and as many as 13 points)

Morphine use 25 to 48 hours after surgery

9 studies (449 people)

People used 5 times more morphine with patient-control of pain medication (could be an increase of as little as 3 times to as much as 8 times more)

*Includes evidence of moderate strength (evidence of low, very low, or unclear strength is not reported here).

Related Topics


Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

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