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Route of administration is one of the determinants of effective postoperative analgesia. Each route has risks and benefits described below. The most widely used are intravenous and oral due to their greater predictability and ease of delivery. Other methods of treatment may become important when standard routes of administration are not available.


Intravenous (IV) medication administration is the most common approach to postoperative pain relief due to ease of delivery, speed of onset, and variety of medications available. Since most patients have an IV placed for their procedure, it is also a guaranteed access point for medications. If a patient does not have IV access, though, this may not be an option.

Pain medications can be delivered via IV either by health-care team or through patient-controlled analgesia (PCA). PCA often results in improved patient satisfaction scoring due to the immediacy and control over the delivery of pain medication. Some studies have shown that PCA administration reduces total opioid administered. Nevertheless, patient pain scores are equivocal to nurse/staff administered IV pain medication.

Patient-controlled analgesia requires patient comprehension, cooperation, and physical ability to depress a button. Also, PCA introduces susceptibility to patient, family, or staff misuse. Finally, there is a risk of dosing errors if machines are not set properly.

Common drug choices for IV administration for postoperative pain include: fentanyl, sufentanil, morphine, meperidine, hydromorphone, methadone, Ketorolac, and acetaminophen.


Orally administered medications are another commonly used method of postoperative (PO) pain control. The PO route is particularly useful in the ambulatory surgery setting. Administration by this route generally has a longer duration of action and allows patients to reach a comfortable state of pain control prior to discharge. This route is easy to use and can be used to control pain in patients without IV access.

The PO route is suboptimal for treatment of severe pain because of limited titration ability and prolonged time to peak effect. It is also not tolerated in patients with postoperative nausea or vomiting. Oral administration of medications may have low bioavailability, and increased side effects with the higher doses required for therapeutic effect.

Common drug choices for PO administration for postoperative pain include: morphine, meperidine, methadone, hydromorphone, oxycodone IR, NSAIDs, and acetaminophen.


The intramuscular (IM) route involves medication injection into the muscle body. The benefit of using this route is the ability to deliver medications without IV access. This route also works for patients unable to tolerate PO. Problems associated with IM administration are pain on injection as well as residual pain at the site of injection. The delivery system via this route is unpredictable because of wide swings in drug concentration, requiring frequent monitoring after administration.

Common drug choices include: ...

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