Thursday, July 7, 2005
This month's J of Palliative Medicine has an interesting gem buried in the correspondence section--a simplified morphine to methadone conversion scheme. Dr. William Plonk averaged published conversion ratios from 5 sources (Lawlor, Cancer 1998, 82:1167–73; Ripamonte, J Clin Oncol 1998, 16:3216–21; Mercadante, J Clin Oncol 1999, 17:3307–12; Mercadante, J Clin Oncol 2001, 19:2898–904; Mercadante, Supp Care Cancer 2003, 11:326–31), performed some math, and came up with this formula:
Estimated daily oral methadone dose (in mg) = (Daily oral morphine equivalents in mg)/15 + 15.
So 200mg of oral morphine a day converts to 28mg of oral methadone a day.