A long-term open, clinical and pharmacokinetic assessment of sublingual buprenorphine in patients suffering from chronic pain.

Buprenorphine was administered as sublingual tablets to 70 patients suffering from chronic pain of malignant or non-malignant origin. Daily doses ranging from 0.4 mg to 3.2 mg were administered and good analgesia was reported by the majority of patients. The most common unwanted effects were drowsiness/sleepiness, nausea and/or vomiting and sweating which appeared to be dose related but the incidence of dizziness was not related to daily dose. The incidence of all these unwanted effects except drowsiness/sleepiness decreased after the first week's treatment. No buprenorphine related changes in vital signs or laboratory values were observed and no signs of tolerance or physical dependence were seen in the short term period after discontinuation of treatment. A significant positive correlation between buprenorphine plasma concentration and daily dose was observed but there was no correlation between plasma levels and pain relief.