A dose of one analgesic that is equivalent in pain-relieving effects to that of another analgesic - the dose in steady state providing the same analgesic response.
The equivalent dose has been standardized to 10 mg of parental morphine in most studies.
Items that may influence relative potencies
- Major organ dysfunction, particularly renal and hepatic impairment, but also adrenal insufficiency, hypothyroidism, and abnormal levels of protein binding
- Demography, including race, age, and gender
An equianalgesic chart
is a conversion chart that lists equivalent doses of analgesics. Equianalgesic charts are used for calculation of an equivalent dose (a dose which would offer an equal amount of analgesia) between different analgesics.
Equianalgesic doses need to be calculated when switching from one drug to another, when changing routes of administration, or both.
Adapted from Arnold R and Weissman D. Palliative Care Network of Wisconsin. Fast facts and concepts #36. Calculating opioid dose conversion. Internet. Accessed on January 25, 2016. Available at http://www.mypcnow.org/#!blank/w5nqk