Whenever possible, the enteral route of administration is best as it is the easiest route and offers the most stable pharmacokinetics. If the enteral route is not able to be used or if adequate analgesia is not able to be obtained in a timely manner then intravenous administration should be used. Intramuscular administration is not recommended because it hurts and has unpredictable pharmacokinetics. With a competent patient, the use of an intravenous patient-controlled analgesia (PCA) has been demonstrated to offer the best overall pain management option (see sections on PCA below).
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