Stuart Guthrie1, Thomas Jensen2, Richard C Hartley2, Kanna Ramaesh1, David Lockington3. 1. Tennent Institute of Ophthalmology, Gartnavel General Hospital, 1053 Great Western Road, Glasgow, G12 0YN, UK. 2. WestCHEM School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK. 3. Tennent Institute of Ophthalmology, Gartnavel General Hospital, 1053 Great Western Road, Glasgow, G12 0YN, UK. davidlockington@hotmail.com.
Abstract
PURPOSE: Unpreserved phenylephrine is often used as an off-licence intracameral surgical adjunct during cataract surgery to assist with pupil dilation and/or stabilise the iris in floppy iris syndrome. It can be delivered as a neat 0.2 ml bolus of either 2.5 or 10% strength, or in a range of ad-hoc dilutions. We wished to assess the accuracy of intracameral phenylephrine preparation in clinical practice. METHODS: Phenylephrine 0.2 ml was analysed both neat (2.5 and 10%) and in diluted form (ratio of 1:1 and 1:3). Samples were analysed using the validated spectrophotometric method. RESULTS: A total of 36 samples were analysed. The standard curve showed linearity for phenylephrine (R2 = 0.99). Wide variability was observed across all dilution groups. There was evidence of significant differences in the percentage deviations from intended results between dilutions (p < 0.001). Mean percentage deviation for 1:3 dilution was significantly greater than neat (p = 0.003) and 1:1 dilution (p = 0.001). There was no evidence of a significant difference between 1:1 and neat (p = 0.827). CONCLUSIONS: Current ad-hoc dilution methods used to prepare intracameral phenylephrine are inaccurate and highly variable. Small volume 1 ml syringes should not be used for mixing or dilution of drug. Commercial intracameral phenylephrine products would address dosage concerns and could improve surgical outcomes in cases of poor pupil dilation and/or floppy iris syndrome.
PURPOSE: Unpreserved phenylephrine is often used as an off-licence intracameral surgical adjunct during cataract surgery to assist with pupil dilation and/or stabilise the iris in floppy iris syndrome. It can be delivered as a neat 0.2 ml bolus of either 2.5 or 10% strength, or in a range of ad-hoc dilutions. We wished to assess the accuracy of intracameral phenylephrine preparation in clinical practice. METHODS:Phenylephrine 0.2 ml was analysed both neat (2.5 and 10%) and in diluted form (ratio of 1:1 and 1:3). Samples were analysed using the validated spectrophotometric method. RESULTS: A total of 36 samples were analysed. The standard curve showed linearity for phenylephrine (R2 = 0.99). Wide variability was observed across all dilution groups. There was evidence of significant differences in the percentage deviations from intended results between dilutions (p < 0.001). Mean percentage deviation for 1:3 dilution was significantly greater than neat (p = 0.003) and 1:1 dilution (p = 0.001). There was no evidence of a significant difference between 1:1 and neat (p = 0.827). CONCLUSIONS: Current ad-hoc dilution methods used to prepare intracameral phenylephrine are inaccurate and highly variable. Small volume 1 ml syringes should not be used for mixing or dilution of drug. Commercial intracameral phenylephrine products would address dosage concerns and could improve surgical outcomes in cases of poor pupil dilation and/or floppy iris syndrome.
Authors: Nick Mamalis; Henry F Edelhauser; Daniel G Dawson; Jesse Chew; Russell M LeBoyer; Liliana Werner Journal: J Cataract Refract Surg Date: 2006-02 Impact factor: 3.351
Authors: Ramón Lorente; Victoria de Rojas; Paula Vázquez de Parga; Claudio Moreno; Juan Varela; Maria Luisa Landaluce; Julia Méndez; Betty Lorente Journal: Ophthalmology Date: 2012-06-17 Impact factor: 12.079