Does Oral Acetaminophen Lower Intraocular Pressure?

• The study design is prospective case series. Before treatment, study subjects will have their intraocular pressure measured at 8 am, 10 am, 12 pm and 4 pm. They will then take acetaminophen 650 mg qid for 7 days and the intraocular pressures again measured at 8 am, 10 am, 12 pm, and 4 pm. Subjects will then stop the acetaminophen and return one week later for one more set of intraocular pressure measurements at 8 am, 10 am, 12 pm, and 4 pm. The subjects will receive a reminder, by phone or text message, the day before each visit. Although measurement of intraocular pressure is part of routine clinical care, multiple intraocular pressure measurements over the course of three different days is not.

-- The subjects will not be masked to the intervention. The person measuring the intraocular pressure will be unaware of the purpose of the study, and hence there should be no bias in the measurement of the main outcome measure, intraocular pressure.

• Treatment will occur for 7 days only, and during that time we will not know if the treatment has been successful in lowering the intraocular pressure. The only basis upon which a participant would be removed would be if he or she reported adverse effects from the study medication before the one week.
• The rationale for choosing acetaminophen is that there are data that it may be effective in lowering intraocular pressure. The dose chosen for this study (650 mg qid), is a dosing regimen that is commonly used for the treatment of pain, and is below the maximum recommended daily dose of 3 gm/day. If this dosing scheme does NOT lower intraocular pressure, further investigations are not planned; if it does lower intraocular pressure, further studies will be performed to find the lowest effective dose.
• Acetaminophen has a several decades long safety record as an over the counter medication for the treatment of pain. The dose and route of administration proposed is standard. Many of the participants will likely have used acetaminophen in the past.