Background
We report a case in which stromal deposits were produced due to drug interaction in a 61-year-old patient following phototherapeutic keratectomy (PTK).Methods
In our case, the patient herself added the use of indomethacin eye drops to the prescribed topical antibiotic treatment and eye gel (5× ciprofloxacin plus 3× indomethacin, eye gel overnight) following PTK. At 5 days the central stroma was not reepithelialised; instead, whitish, round deposits were found in the stroma. Mixing indomethacin and ciprofloxacin eye drops 1:1, the pH of the mixture changed to 5.6, and a yellow precipitate was formed; this was analysed by 1H-NMR spectroscopy. To investigate the solubility of the two drugs at the pH of the mixture, the pH of each solution was independently set to 5.6 by addition of hydrochloric acid or sodium hydroxide.Results
In the precipitate both indomethacin and ciprofloxacin were detected. After setting the pH to 5.6, a yellow precipitate was observed in the indomethacin solution; however, the ciprofloxacin solution remained clear.Conclusions
Interaction may occur if ciprofloxacin and indomethacin are used together. It is better to avoid the use of the two drugs at the same time, particularly in the case of a large epithelial defect when stromal deposition of the drugs may be produced.Each author states that he/she has no proprietary interest in the development or marketing of this or any competing instrument or piece of equipment. No financial interests.