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Safety analysis of long-term phenazopyridine use for radiation cystitis

Background Phenazopyridine is a urinary tract analgesic indicated for short-term treatment of irritation in the lower urinary tract. Despite the lack of evidence for extended use, it is often used in varying durations for supportive care for cancer patients with radiation-induced cystitis. The objective of this study was to compare the incidence of adverse drug reactions in patients with radiation cystitis receiving long-term phenazopyridine (>14-day supply) compared to a matched comparator group. Methods This retrospective cohort study compared adverse events among cancer patients with and without phenazopyridine exposure. Included patients received radiation and at least one chronic medication between 1 July 2008 and 30 June 2017. The phenazopyridine group also received >14-day supply of phenazopyridine during the study period. Patients were matched based on gender, age (±5 years), cancer diagnosis, and palliative or curative treatment intent. Data collection occurred at baseline, during the time of presumed exposure, and through the end of the study period for surveillance purposes. Results A total of 272 patients received phenazopyridine for >14-day supply during the study period. Of these, 90 patients were included and matched to an equal number of patients in the comparator group. The included patients were similar between groups and were largely male with a diagnosis of prostate cancer. Most patients received between a 30- and 60-day supply of phenazopyridine. There were a total of 13 adverse drug reactions in the phenazopyridine group and 18 in the comparator group (p = 0.32). No differences were identified between the phenazopyridine and comparator groups for the incidence of individual adverse drug reactions, emergency department visits, hospitalizations, or new diagnoses of hepatocellular or colorectal cancer. Conclusion There was no difference in adverse drug reactions among patients receiving phenazopyridine for >14 days compared to a matched comparator group. The overall incidence of adverse events in both groups was low.