Hydromorphone levels and pain control in patients with severe chronic pain.

To better understand the use of narcotic analgesics, the hydromorphone concentration was measured in serum samples from 43 patients with chronic severe pain who were receiving this drug. At the time of blood sampling, pain intensity, mood, and cognitive performance were assessed. There was large individual variation in the dose-drug level relationship. Seven patients with bone or soft tissue pain and drug levels of greater than or equal to 4 ng/ml had good pain control, whereas 10 did not. None of 15 patients with levels less than 4 ng/ml had pain control, despite drug doses similar to those given patients with higher levels. Thus 60% of the patients without control of their pain had hydromorphone levels below the lowest level that produced pain control. No patient with pain from nerve infiltration or compression had good pain control, irrespective of the drug level or dose. Poor mood correlated with high pain intensity and low drug level. Impaired cognitive performance was not related to drug level. Knowing that there is a low concentration of narcotic in the blood of a patient with chronic severe pain who is receiving high drug doses and who shows lack of both efficacy and side effects may reassure health care professionals that further narcotic dosage escalation is appropriate.