When trying a new eye drop, how long to determine its efficacy?
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5 months ago
BrianB • 80
@brianb

When trying a new (different) eye drop prescription, how long is reasonable before making a determination on the drop's effectiveness (or lack of)?

I recently tried Rhopressa, which seemed ok for the first few days, but then I was seeing pressure spikes (as measured at with Icare Home) that I didn't have with Brimonidine.

I am now looking at trying something other options, and would like to hear others' experiences (and/or what is general medical guidance) on how long one should expect to use a new drop before deciding if it is working or not.

rx:medications eye-drops • 140 views
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5 months ago
david 3.2k
@david_fe

The exact answer depends on the drop you are switching from as well as your own body chemistry. Your genetics can determine how quickly you clear drugs from your system. However, I can give you a rule of thumb.

At a minimum, I would give it two weeks. In most cases, the prior medications will have from zero to negligible effects two weeks after being discontinued.

Therefore, the several days of home intraocular pressure monitoring toward the end of those that period can be assumed to be free of any influence from the prior medication(s).

However, if you want to be even more confident, you could give it four weeks. By four weeks you can be almost absolutely certain that all the prior medication is out of your system or at least no longer producing any effect on your IOP.

My personal experience is that timolol, normally a very short-lived glaucoma medication, continues to exert strong effects on my IOP for more than a week after a single drop. Therefore, I would certainly have to allow two weeks washout before I can be confident my IOP is no longer reduced because of that medication.

Various published studies use different washout periods, but four weeks is a common one. I seem to recall reading some studies with two week washout periods. That duration seems reasonable for home monnitoring, but for a clinical study I think it is too short.

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I guess I didn't give the Rhopressa enough time then? Or did I?

On Dr's instructions I stopped Brimonidine for a week (during which time I saw IOP numbers in general a couple points higher). Then started the Rhopressa, which seemed to be OK for 5 days or so, but then I was getting some significant spikes that I had not seen previously. I stopped the Rhopressa and went back to the Brimonidine and I stopped seeing the spikes. Is it reasonable then to conclude the Rohpressa was the culprit? (seemed so to me)

I'm now looking at trying some different drops and am just looking for some general guidance on how long before making conclusions.

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