Oral versus topical carbonic anhydrase inhibitors use not tied to serious adverse events in glaucoma: JAMA

Canada: A recent study in the journal JAMA Ophthalmology shows that the risk of a serious adverse reaction after the prescription of an oral or topical carbonic anhydrase inhibitor is low and similar between agents. Given, the low risk, the researchers suggest reconsidering the reluctance toward prescribing an oral carbonic anhydrase inhibitor.

Glaucoma is a group of eye conditions that damages the optic nerve and is known to affect more than 60 million patients worldwide. Carbonic anhydrase inhibitors (CAIs) decrease aqueous humor production, and hence lower intraocular pressure. It is seen that ophthalmologists are reluctant to prescribe oral carbonic anhydrase inhibitors owing to their potential for life-threatening systemic adverse reactions. 

Against the above background, Marko M. Popovic, Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, Ontario, Canada, and colleagues aimed to conduct a population-based analysis of the safety of oral or topical carbonic anhydrase inhibitors in clinical care. 

The study was conducted in Ontario, Canada. The study identified consecutive patients older than 65 years who have prescribed an oral or topical carbonic anhydrase inhibitor between January 1, 1995, and January 1, 2020. Patients were matched 1-to-1 based on sex, age, and diabetes status.

Time zero was defined as the date of the first identified prescription for the medication, and the primary analysis focused on the first 120 days of follow-up. The primary endpoint was a severe complicated adverse event of either Stevens-Johnson syndrome, toxic epidermal necrolysis, or aplastic anemia.

Overall, during the 25-year study period, 128 942 matched patients have initiated an oral or topical carbonic anhydrase inhibitor. The mean age was 75 years, 71 958 (55.8%) were women, and 25 058 (19.4%) had a diagnosis of diabetes. 

"This population-level analysis showed that oral CAIs were a safe treatment with a low incidence of serious adverse events," wrote the authors. "When compared with topical CAIs, there was a modest difference in the risk of a SCAR event and no increased risk of a general adverse drug reaction."

However, the researchers conclude that oral CAIs should not be initiated casually, and appropriately informed consent discussions must be had with patients initiating these agents. At the same time, they suggest reconsidering the reluctance toward prescribing oral CAIs, given the low risk of severe adverse events.

Reference:

Popovic MM, Schlenker MB, Thiruchelvam D, Redelmeier DA. Serious Adverse Events of Oral and Topical Carbonic Anhydrase Inhibitors. JAMA Ophthalmol. Published online January 27, 2022. doi:10.1001/jamaophthalmol.2021.5977