Method to change route of administration of an analgesic:
- Calculate total 24 hour dose used in current mode of administration (combine standing and breakthrough dosing used)
- Look up equianalgesic value of analgesic: morphine ratio IV:PO = 1:3, so 30 mg of oral morphine is equal to 10 mg of IV morphine (IV morphine is 3 times stronger than oral!). Do the math:
- Always consider use of long-acting oral formulations for consistent analgesia, such as MS Contin which can be dosed every 12 hours.
- Calculate breakthrough or rescue does: typically 10-20% of total 24 hour dose available every 2-4 hours PO, every 30-60 minutes IM or SC, and every 10-20 minutes IV, as needed.
Table of equinalgesic doses of opioid analgesics