Background and importance Insulin eye drops are an effective treatment for corneal neurotrophic ulcers due to the action of insulin as a tissue growth factor. Owing to the lack of studies on the stability of this eye drops, in clinical practice it is not possible to give them for more than 7 days of use. The purpose of this study was to assess whether the stability could be increased, making the preparation and dispensing by the Pharmacy Service easier, as well as making it more comfortable for the patient.
Aim and objectives The objective was to study the chemical stability and physical compatibility of eye drops of human insulin (Humulina and Actrapid) at 1 UI/mL, diluted in Systane, Liquifilm or 0.9% sodium chloride (0.9% NaCl), in polyethylene bottles, protected from light, at 24°C or 4.5°C, for 30 days.
Material and methods Three preparations were prepared for each condition. At the time of analysis, one sample for each preparation was analysed by high performance liquid chromatography. The time at which human insulin retained 90% of the initial concentration (T90) was obtained for each preparation. The method was validated according to the International Conference on Harmonisation Q2 (R1). Physical stability was evaluated by visual inspection, gravimetric analysis and pH measurement.
Results Humilina preparations, T90 was: (a) with Systane: 9 days at 4.5°C, 7 days at 24°C; (b) with Liquifilm: 9 hours at 4.5°C, 10 hours at 24°C; (c) with 0.9% NaCl: 1 day at 4.5°C, 15 hours at 24°C. Actrapid preparations, T90 was: (d) with Systane: 10 days at 4.5°C and 24°C; (e) with Liquifilm: 17 hours at 4.5°C, 6 hours at 24°C; (f) with 0.9% NaCl: 4 days at 4.5°C, 3 days at 24°C. During the study, neither changes in colour nor losses of weight were observed in the preparations assayed: variations of pH were higher than 5% from day 2 in all preparations with Humulina and Actrapid in 0.9% NaCl.
Conclusion and relevance Eye drops of human insulin (Humulina or Actrapid) at 1 UI/mL diluted in Systane, in polyethylene bottles and protected from light, can be used in clinical practice.
Conflict of interest No conflict of interest
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