Inter- and intra-patient variability in breakthrough pain episodes of opioid-treated patients with underlying chronic pain. An observational, prospective and multicenter study

Resumen

Objectives: Since, to date, there are few epidemiological data assessing the diversity in the characteristics of breakthrough pain episodes, the present study was performed to assess the intra-individual variability in the episodes of breakthrough pain in patients with underlying chronic pain controlled with opioids. Methods: An observational, prospective and multicenter study (CADI study) was conducted in the context of the routine clinical practice of Spanish pain specialists recruiting opioid-treated patients with underlying chronic pain. Data were recorded in three visits (baseline, at 7 and 28 days post-inclusion) and by the patient on a patient´s diary card, specifically designed to characterise the first 8 breakthrough pain episodes (type, intensity –using 100 mm Visual Analog Scale- and duration of pain), to assess the intra-individual and inter-individual variability in the intensity, duration and typology of episodes of breakthrough pain. Results: 50 opioid-treated patients were recruited (23 with oncologic pain and 27 with non oncologic pain, mean age of 61.1 years, 62% females). For all three parameters, inter-patient variability was higher than intra-patient variability throughout the episodes. Nevertheless, we found intra-patient variability in maximum pain intensity, pain intensity at the end of the episode, pain relief and duration of the episode. Conclusions: This is the first study to quantify the intra-patient variability of breakthrough pain. The results show a great variability in terms of intensity and duration of the episode and its typology. Although inter-patient variability is higher, the intra-patient variability is important enough to be taken into account in optimizing the approach and treatment selection.