Prescription drug warning labels (PWLs), small, colorful, auxiliary stickers applied by pharmacy personnel on prescription vials, are used to provide important, drug-specific information about medications. At present, the required information and the presentation of said labels is not standardized in the US, and they are not regulated by the FDA (Ault 2007). This is despite the fact that, these labels contain information that is critical to the safe and effective use of the products contained within.

Thirty-three subjects from two populations (18-29 and 50+) were characterized in a variety of ways and tested to objectively examine the performance of PWLs in five color contrasts. Tests of label performance included: eye tracking, recall and recognition and legibility. Data were evaluated in various ways.

Statistical analysis was performed using mixed models. There was not enough evidence to conclude an effect of color contrast on the noticeability of the PWL's, although findings indicated that subjects were more likely to notice and spend more time on the large white pharmacy label as compared to the cap and the PWL. It was revealed that subjects from the younger population were more likely to recognize the PWL's they had seen. It was also identified that certain categories of information (dosage, patient information) were recalled more than the others. Legibility findings were consistent with previous studies with the black on white color contrast being the easiest to read.