Sterility and stability of manually diluted 2.5 % phenylephrine hydrochloride for pupillary dilatation

Abstract

Introduction : Comparing with 10 % phenylephrine hydrochloride, the 2.5 % concentration is potentially safer, and has been proved to be equally effective in pupillary dilatation for posterior eye segment examination, but it is not commercially available in Thailand.

Objective : To study the sterility and stability of manually diluted 2.5 % phenylephrine hydrochloride solutions.

Setting : Outpatient eye clinic, King Chulalongkorn Memorial Hospital.

Research design : Clinical experimental study.

Methods : The 10% phenylephrine hydrochloride was manually diluted with normal saline solution, Tears Naturale II^® eye drop, balanced salt solution and Opsil tears^® eye drop to make four kinds of 2.5 % phenylephrine hydrochloride solutions. All of the solutions were cultured on day 0, 1, 3, 5, 7, 10, and 14 after dilution to detect microbial contamination. The 2.5 % solutions, in combination with 1 % tropicamide, were then applied to the patients 0, 1, 3, 5, 7, 10, and 14 days after the dilution. The pupillary size before and after application of the solutions was measured under slit lamp biomicroscope.

Results : All of the microbial culture results were negative. A total of 189 eyes from 101 patients (29 men, 72 women) were recruited. The mean age of the patient was 50.6 + 17.3 years. The normal saline solution group included 28 patients, the Tear Naturale II^® eye drop group included 22 patients, the balanced salt solution group included 25 patients and the Opsil tears^® eye drop group included 26 patients. The manually diluted 2.5 % phenylephrine hydrochloride solutions can increase the pupillary size to approximate 7.1 to 8.8 mm.

Conclusion : All of the manually diluted 2.5 % phenylephrine hydrochloride solutions in combination with 1% tropicamide has sufficient clinical efficacy for the pupillary dilatation. The sterility and stability of the solutions maintained for at least 2 weeks.