The Conversion Ratio From Intravenous Hydromorphone to Oral Opioids in Cancer Patients

Context The lack of knowledge of the accurate conversion ratio (CR) between intravenous (IV) and oral hydromorphone and opioid rotation ratio (ORR) between IV hydromorphone and oral morphine equivalent daily dose (MEDD) may lead to poorly controlled pain or overdosing in cancer inpatients. Objectives We aimed to determine the CR and ORR from IV hydromorphone to oral hydromorphone and MEDD (obtained from oral morphine and oxycodone). Methods A total of 4745 consecutive inpatient palliative care consults during 2010–14 were reviewed for conversions from IV hydromorphone to oral hydromorphone, morphine or oxycodone. Patient characteristics, symptoms, and opioid doses were determined in patients successfully discharged on oral opioids without readmission within one week. Linear regression analysis was used to estimate the CR or ORR between the 24 hour IV hydromorphone mg dose before conversion and the oral opioid mg dose used before discharge. Results Among 394 patients on IV hydromorphone, 147 underwent conversion to oral hydromorphone and 247 underwent rotation to oral morphine (163) or oxycodone (84). The median (interquartile range) CR from IV to PO hydromorphone was 2.5 (2.14–2.75) with correlation of 0.95 (P < 0.0001). The median ORR (interquartile range) from IV hydromorphone to MEDD was 11.46 (9.84–13.00) with correlation of 0.93(P < 0.0001). The median ORR was 11.54 in patients receiving <30 mg of IV hydromorphone/day and 9.86 in patients receiving ≥30 mg (P = 0.0004). Conclusion Our study found that 1 mg of IV hydromorphone is equivalent to 2.5 mg of oral hydromorphone and 11.46 mg of MEDD. Hydromorphone at doses ≥30 mg/day may require a lower ORR to other opioids.