Breakthrough pain is not a fixed fraction of constant cancer pain

This journal recently published a paper by Currow et al., entitled "A randomised, double-blind, crossover, dose ranging study to determine the optimal dose of oral opioid to treat breakthrough pain for patients with advanced cancer already established on regular opioids" (Currow et al., 2010). Currow et al. demonstrated that for breakthrough pain (BTP) there were no differences between giving rescue opioids doses of 1/6, 1/8 or 1/12 of the scheduled daily opioid dose.