Purpose The aim of the present study was to assess the longterm tolerability and efficacy of intranasal fentanyl (INFS) in opioid-tolerant patients with breakthrough cancer pain (BTP).Patients and methods A 6 months, observational, prospective, cohort study design was employed to follow advanced cancer patients with BTP receiving INFS under routine clinical practice. Eligible adult cancer patients suffering from BTP had been prescribed INFS at effective doses. Data were collected at T0 and at month intervals for six months. The principal outcomes were the evaluation of possible serious adverse effects with prolonged use of INFS, the efficacy of BTP treatment with INFS, the quality of sleep, the rate of INFS discontinuation, and reasons for that.Results Seventy-five patients were surveyed. Thirty-four patients (45.3 %) had a follow-up at 3 months, and twelve patients (16 %) were followed up at 6 months. The mean opioid doses, expressed as oral morphine equivalents, ranged 111-180 mg/day, while the mean INFS doses were 87-119 μg. Adverse effects were reported in a minority of patients and were considered to be associated with opioid therapy used for background pain. The quality of sleep significantly improved during the first 3-4 months. Finally, efficacy based on a general impression regarding the efficacy of INFS was good-excellent in most patients and statistically improved in time up to the third month. Conclusion The long-term use of INFS in advanced cancer patients is effective and safe. No serious adverse effects were found up to six months of assessment. The level of quality of sleep and patients' satisfaction was relatively good, considering the advanced stage of disease.
