Which statement best summarizes the relationship between drug classes and IOP lowering?

• A. They have no interaction
• B. They can have additive effects when used together
• C. They always cancel each other out
• D. They produce a fixed amount of reduction regardless of combination

Answer: (B)

Different drug classes lower IOP through distinct mechanisms, targeting both production and outflow of aqueous humor. When these different mechanisms are used together, their effects tend to add up, producing a greater total reduction in intraocular pressure than any one drug alone. This is why additive effects when used together best describe how drug classes interact to lower IOP.

It isn’t accurate to say there’s no interaction, or that they always cancel each other out, or that the reduction is the same no matter what combination is used. The actual drop depends on the drugs chosen and the patient’s baseline IOP, but the general principle is that combining agents from different classes can yield greater IOP lowering than a single agent.