Which statement is true about combining PGAs with other drug classes?

• A. It is always contraindicated to combine PGAs with other classes
• B. PGAs should never be used in combination with beta-blockers
• C. There is potential additive effect when combining across drug classes
• D. Combining PGAs with CAIs negates the effect

Answer: (C)

The idea being tested is that prostaglandin analogs can be used with other glaucoma medications to lower eye pressure more effectively because they work through different mechanisms. Prostaglandin analogs primarily increase outflow through the uveoscleral pathway, while beta-blockers and carbonic anhydrase inhibitors reduce the production of aqueous humor, and alpha agonists can do a bit of both. Because these drugs act on separate parts of the aqueous humor dynamics, their effects add up when used together, giving an additive IOP-lowering effect. This is why combinations like a prostaglandin analog with a beta-blocker are commonly used and why fixed-dose combinations that pair these agents are available. It’s not true that combining PGAs with other classes is always contraindicated, nor that they must never be used with beta-blockers, and there’s no rule that combining with CAIs negates the effect. Just be mindful that more medications can bring more side effects and adherence challenges, so monitoring and patient counseling are important.