Recent use of tamsulosin significantly increases the risk of serious adverse events during cataract surgery, although use of other alpha-blockers does not, according to a retrospective observational study.
The age range of those people having cataract surgery, and those being treated for benign prostatic hypertrophy (BPH) is similar, thus many men with BPH will have cataract surgery. Tamsulosin is a selective adrenergic alpha-1a receptor blocker widely used in the treatment of BPH, however these receptors are also present in the muscle that dilates the iris of the eye. As a result, tamsulosin may also impede mydriasis during surgery and lead to intra-operative floppy iris syndrome (IFIS): this is associated with a range of complications during cataract surgery. The authors of this study used data from Canadian healthcare administrative databases to assess the risk of such complications associated with use of tamsulosin and other alpha-blockers.
They obtained data from linked healthcare databases covering the population of Ontario to construct a study population of men aged over 65 who had cataract surgery over the period 2002 to 2007. Cases were those who had an adverse ophthalmological surgical outcome within 14 days of operation, and controls were selected from those who had no such adverse event. Each case was matched with up to four controls by age, surgeon performing the surgery, and year of surgery. Drug exposure of interest was tamsulosin, however exposure to other alpha-blockers was also assessed. Primary outcome was the risk of a composite of serious adverse events associated with tamsulosin and other alpha-blocker exposure compared to controls. Exposure was divided as recent, within the 14 days before surgery, and previous, within 14 days to one year before surgery. As a sensitivity analysis, the risk associated with exposure to proton-pump inhibitors (PPI) was also assessed, as there is no reason to expect that these drugs have any relevant effects.
There were 96,128 men who had cataract surgery during the study period: of these 3,550 (3.7%) had recent exposure to tamsulosin and 1,006 (1.1%) had previous exposure to tamsulosin; 7,426 (7.7%) had recent exposure to other alpha-blocking medications and 1,683 (1.1%) had previous exposure. There were 284 case patients who had a relevant adverse event in the 14 days after surgery, and 280 of these were matched with 1,102 controls.
In the primary analysis, 21 case patients (7.5%) and 30 control patients (2.7%) received tamsulosin in the 14 days before surgery (adjusted odds ratio 2.33; 95% CI, 1.22 to 4.43). In the analysis of other alpha-blockers, 21 case patients (7.5%) and 88 control patients (8.0%) received the medication in the 14 days preceding surgery (adjusted OR, 0.91; 95% CI, 0.54 to 1.54). There was no significant association with previous exposure to either tamsulosin or other alpha-blockers, nor with exposure to PPI. The authors calculated an estimate for number needed to harm of 255 (95% CI, 99 to 1,666).
Based on their analysis, the authors conclude that recent exposure to tamsulosin was associated with a significantly increased risk of serious complications following surgery for cataract. They discuss the strengths and limitations of their study, and comment on the possible mechanism of the effect. They note that while they did not find a statistically significant effect with other alpha-blockers, the 95% CI did not exclude a smaller but clinically significant increase in risk. They suggest that because the combination of tamsulosin use and cataract surgery will be fairly common, clinicians and patients should be aware of the potential risk.
An accompanying editorial discusses the study.