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Buffering tetracaine increases instillation pain in healthy patients
Lowered pH is not the key to lowering pain from instillation of anesthetic eye drops, a study suggests.
Buffering of tetracaine HCl eyedrops increased the pain of their instillation significantly, according to researchers at Indiana University School of Medicine.
Christopher Weaver, MD, and colleagues randomized 60 healthy volunteers to receive either 2 drops of buffered or 2 drops of plain tetracaine in a randomly assigned eye. After a mean washout period of 24 days, participants had 2 drops of the other medication instilled in the same eye. Instillation pain was recorded on a visual analog scale (VAS) immediately and 5 minutes after instillation.
Immediately after instillation, the mean VAS score for buffered tetracaine was 29.1 mm, and the mean VAS score for plain tetracaine was 16 mm.
The study is published in the June issue of Annals of Emergency Medicine.