Morphine PO:IV = 60:10 for opioid naive patient, 30:10 for others.

Oxycodone - may be used chronically for severe pain only when it is not combined with aspirin or acetaminophen-see precautions for Hydrocodone.

Methadone - is an excellent choice for opioid rotation. Where other opioids can be converted based on a fixed ratio, the starting methadone dose decreases proportionately as the dose of the previous drug increases. Put another way, the morphine:methadone ratio changes as the morphine dose increases. Calculate the equianalgesic dose using the following method, then reduce the calculated dose by 25-50% to determine the starting dose. The following table shows PO morphine:PO methadone.

Levorphanol - has long half life and begins to accumulate on days 2-3.

Transdermal Fentanyl (fentanyl patch) - 50 mcg/h patch = Morphine 100mg PO/24 h = 16 mg PO q4h = 1.4 mg/h IV.

Meperidine - should be used only for very short term moderate pain. It is very short acting (dose must be repeated at least every 3 hours) and rapidly accumulates neurotoxic metabolites.

Codeine - dosing is limited by the potential toxicities of the acetaminophen with which it is often combined. Side effects are more problematic than those for equianalgesic doses of other opioids. It should be used for short term moderate pain only. Unlike most other opioids, analgesia does not increase with doses greater than 200 mg ("ceiling dose").

Propoxyphene - is a weak opioid that rapidly accumulates neurotoxic metabolites and should not be used for severe or chronic pain.

Hydrocodone - dosing is limited by the potential toxicities of the acetaminophen or ibuprofen with which it is combined. It should be used for short term moderate pain only.