Tamsulosin for BPH associated with hospitalizations for hypotension

Tamsulosin for benign prostatic hyperplasia (BPH) may be associated with about twice the rate of severe hypotension requiring hospitalization during the first 8 weeks of treatment and the first 8 weeks after restarting treatment, researchers found.

To characterize the risk of hypotension requiring hospitalization among men ages 40 to 85 who were treated with tamsulosin (Flomax), researchers designed a population-based, retrospective cohort study based on claims data from a private insurer database comprising 102 U.S. health care plans for more than 68 million patients from January 2001 through June 2011.

Researchers looked at all men who received tamsulosin or a 5α reductase inhibitor (5ARI) after a minimum of 6 months of enrollment to test a between-patient methodology, and then a self-controlled case series to test within-patient methodology. Results appeared online Nov. 5 at BMJ.

Among 383,567 new users of study drugs (tamsulosin, n=297,596; 5ARI, n=85,971), there were 2,562 hospitalizations for severe hypotension. Rates of hypotension were higher for tamsulosin (42.4 events per 10,000 person-years) than for 5ARIs (31.3 events per 10,000 person-years). The cohort analysis found an increased rate of hypotension in the tamsulosin group during weeks 1 to 4 (rate ratio [RR], 2.12; 95% CI, 1.29 to 3.04) and weeks 5 to 8 (RR, 1.51; 95% CI, 1.04 to 2.18). There was no significant increase during weeks 9 to 12 (RR, 1.34; 95% CI, 0.97 to 1.84).

After tamsulosin was restarted, rates of hypotension also increased at weeks 1 to 4 (RR, 1.84; 95% CI, 1.46 to 2.33) and 5 to 8 (RR, 1.85; 95% CI, 1.45 to 2.36), although the risk increase during weeks 9 to 12 was not significant (RR, 1.34; 95% CI, 0.97 to 1.84). Rates of hypotension increased during maintenance treatment (RR, 1.19; 95% CI, 1.07 to 1.32).

The researchers noted that the self-controlled case series yielded similar results as the cohort analysis. After new drug treatment was started, hypotension risk rose during weeks 1 to 4 of new use (RR, 2.56; 95% CI, 2.15 to 3.05), weeks 5 to 8 (RR, 1.66; 95% CI, 1.30 to 2.11) and weeks 9 to 12 (RR, 1.54; 95% CI, 1.19 to 2.01). After treatment was restarted, hypotension rose during weeks 1 to 4 (RR, 1.58; 95% CI, 1.24 to 2.01) and weeks 5 to 8 (RR, 1.60; 95% CI, 1.25 to 2.05) and during maintenance drug treatment (RR, 1.38; 95% CI, 1.21 to 1.57).

Lower rate ratios for hypotension in the later time blocks of 5 to 8 weeks or 9 to 12 weeks may represent hypotension risk among patients who tolerated the drug during earlier periods, the researchers noted. They added that patients who are adherent to tamsulosin may also achieve better control of lower urinary tract symptoms, which could result in a lower risk of falls. The researchers advised physicians to counsel patients about the drug's apparent “first dose phenomenon.”