This audio article is from VisualFieldTest.com.
Read the full article here: https://visualfieldtest.com/en/washout-and-rescue-protocols-in-april-2026-iop-lowering-studies
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Excerpt:
Introduction
Clinical trials of new glaucoma (intraocular-pressure–lowering) medications often pause patients’ existing eye drops to establish a clear “untreated” baseline pressure. This is known as a washout period (). By measuring eye pressure after stopping prior treatment, researchers can accurately judge how much the new drug lowers pressure. However, taking patients off therapy raises safety concerns (pressure can rebound) and can cause some people to fail screening. Trials therefore include strict rescue rules (to restart treatment if pressure gets too high) and careful monitoring. Understanding these washout and rescue protocols helps explain why trial results may differ from everyday practice.
Washout Durations and Sequences by Medication Class
Trials use different washout lengths for different drug classes, based on how long medications linger in the eye. In general:
Prostaglandin analogs (PGAs) (e.g. latanoprost, travoprost, bimatoprost): Washout periods are often around 4 to 8 weeks. A systematic review found that patients typically returned to baseline pressure about 4–5 weeks after stopping latanoprost (). However, PGA effects can variably persist — one study found some patients still had slightly lowered pressure 8 weeks after stopping latanoprost (). Travoprost and bimatoprost also generally need several weeks; most studies use ~4 weeks, although evidence is limited (). Patients on PGAs may undergo multiple checks up to 6–8 weeks after stopping.
Beta-blockers (e.g. timolol): These are typically washed out by stopping the drop for 4 weeks. Research showed that a 2-week break is usually too short (). After stopping timolol, pressure often edges back toward a higher baseline by 3–4 weeks.
Alpha-2 agonists (brimonidine): These often require about 4–5 weeks off. In one trial, 15 patients washed out brimonidine over 5 weeks to reach baseline ().
Carbonic anhydrase inhibitors (CAIs) (dorzolamide, brinzolamide): Although less well studied, trials commonly use around 2–4 weeks off, as their effects diminish more quickly than PGAs.
Miotics (e.g. pilocarpine): These have a very short duration of effect. Usually a break of 1–2 weeks suffices. (Miotics are rarely used long-term today.)
In trials where patients are on more than one medication, the protocols may pause all drops at once or sometimes stagger them. Typically all prior medications are stopped together and sufficient time is allowed for the slowest drug to clear. The washout lengths above are chosen so that most patients return to their true “untreated” IOP. As noted by Stewart et al., too short a washout might make a new drug look less effective, while an unnecessarily long washout only prolongs high risk pressure ().
Stewart and colleagues found, for example, that stopping brimonidine needed about 5 weeks to return to baseline, whereas stopping latanoprost sometimes took up to 8 weeks (). (They also showed that travoprost effects were not fully gone after 2 weeks ().) Because evidence is limited, many trials simply follow “industry standards” (often 4–6 week washouts for PGAs and 4 weeks for older drugs) based on these and other data.
Rescue Criteria and Safety Monitoring
During washout, patient safety is paramount. Trials define rescue criteria
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