(P-580) 5-alpha Reductase Inhibitors and the Risk of Anemia Among Men with Benign Prostatic Hyperplasia

Background: Although 5-alpha reductase inhibitors (5αRIs) are effective for the treatment of benign prostatic hyperplasia, their antiandrogenic effects could increase the risk of anemia. However, few studies have examined this potential adverse drug reaction.

Objectives: To compare the rate of anemia among men with incident BPH prescribed 5αRIs to that of men prescribed α-blockers in the United Kingdom (UK).

Methods: We conducted a matched, active comparator, new-user cohort study using the UK’s Clinical Practice Research Datalink (CPRD Gold). The study population consisted of men aged 40+ years with incident BPH who initiated 5αRIs or α-blockers between January 1st, 1998, and February 20, 2019. The date of this first 5αRI or α-blocker prescription defined cohort entry. Men with a prior diagnosis of anemia or prostate cancer were excluded. Men who initiated 5αRIs were matched 1:1 on propensity score to men who initiated α-blockers. We defined 5αRIs and α-blockers exposure using an as-treated approach. The primary endpoint was anemia, defined by a hemoglobin measurement below 130 g/l based on the World Health Organization criteria. Secondary endpoints were mild (129-110g/l), moderate (109-80g/l), and severe ( <80g/l) anemia. We used Cox-proportional hazards models to estimate hazard ratios (HR) and 95% confidence interval (CIs) for anemia.

Results: From a base cohort of 140,738 men with incident BPH, 9,429 new users of 5αRIs were matched to 9,429 new users of α-blockers. These patients generated 7,684 and 5,940 person-years (PYs) of follow-up, respectively. The median age was 72 years (interquartile range: 65-78 years). The propensity score matching produced a well-balanced cohort for patient characteristics, with all characteristics having standardized differences of ≤ 0.1. A total of 2,865 new users of 5αRIs and 2,407 new users of α-blockers developed anemia, representing rates of 37.3 (95% CI: 35.9-38.7) and 40.5 (95% CI: 38.9-42.2) per 100 PYs, respectively. 5αRIs was not associated with an increased risk of anemia compared to α-blockers (HR: 0.95, 95% CI: 0.90-1.00). The secondary analyses showed a 24% increased risk of mild anemia with 5αRIs compared to α-blockers (HR: 1.24, 95% CI: 1.05-1.47). The HRs for moderate and severe anemia were 1.27 (95% CI: 0.96-1.68) and 0.97 (95% CI: 0.92, 1.03), respectively.

Conclusions: 5αRIs were not associated with an increased risk of anemia compared to α-blockers among men with BPH. Although there is some evidence of modest increases in mild and moderate anemia that suggest the need for patient monitoring, this study provides reassurance regarding the anemia risk of 5αRIs in men with BPH.