Increased risk of severe hypotension in men treated with tamsulosin

By MD Will Boggs

NEW YORK (Reuters Health) - Especially after starting or restarting treatment for benign prostatic hyperplasia, tamsulosin appears to be associated with an increased risk of severe hypotension, according to a retrospective cohort study and self-controlled case series.

"Our data suggest tamsulosin increases the risk for hypotension in a similar fashion to terazosin and other non-selective alpha-blockers, at drug initiation and restart," said Dr. Mahyar Etminan from University of British Columbia in Vancouver, Canada. "This information should be conveyed to prescribing physicians to inform appropriate counseling strategies."

"Simple messages to patients, such as getting out of bed slowly to counteract the rapid onset of orthostatic hypotension, taking the first dosage at nighttime to assess dizziness, or entering the recumbent position after faintness may help reduce unnecessary hospitalizations," Dr. Etminan told Reuters Health by email.

Because tamsulosin is associated with lower rates of asthenia, dizziness and severe hypotension in clinical trials than are non-selective alpha1 blockers such as terazosin and doxazosin, the drug carries a warning for hypotension and syncope but not the black box warning of the less selective alpha blockers in its class.

Dr. Etminan and colleagues used data from the IMS Lifelink database to study the risk of severe hypotension at time-varying intervals during the course of tamsulosin treatment in middle-aged and older men with benign prostatic hyperplasia.

The overall incidence of hypotension was 29.1 events per 10,000 person-years. The incidence was higher among men taking tamsulosin (42.4 events per 10,000 py) than among men taking 5-alpha-reductase inhibitors (31.3 events per 10,000 py).

In the cohort analysis, the risk of severe hypotension was increased more than two-fold during the first four weeks of treatment with tamsulosin and by 51% during weeks 5 through 8 (but not during weeks 8 through 12).

Similarly, upon restarting tamsulosin treatment, the risk of severe hypotension increased by 84% during weeks 1 through 4 and by 85% during weeks 5 through 8.

Maintenance treatment was associated with only a 16% higher risk of hypotension, the researchers report in BMJ, online November 5. Results of the self-controlled case series (using the same database) yielded similar results.

"It should also be noted that our outcome was intended to capture severe events requiring hospitalization, but not small changes in blood pressure," Dr. Etminan said. "The extent to which patients experience orthostatic hypotension in clinical practice is likely greater than for hospital admission for hypotension."

"While studies have shown tamsulosin has a higher unbound drug fraction in the prostate than in the plasma, making the argument for uroselectivity, our results show that hypotension is still a concern with this medication," Dr. Etminan concluded. "Our main message is that physicians and patients should be aware of this potential adverse event."

SOURCE: http://bit.ly/1dDfRy2

BMJ 2013.

(c) Copyright Thomson Reuters 2013. Click For Restrictions - http://about.reuters.com/fulllegal.asp