LOOK-ALIKE SOUND-ALIKE ERRORS WITHIN PHARMACY FILLING ERRORS: A FIVE-YEAR EVALUATION OF TALL MAN LETTERING IN A MALAYSIAN PUBLIC HOSPITAL

Abstract

Background and Objectives: Tall Man lettering (TML) is a recommended strategy to reduce Look-Alike Sound-Alike (LASA) medication errors. However, real-world data evaluating its impact in Malaysian hospital pharmacy settings remains limited. This study aimed to characterise pharmacy filling errors over five years and examine the proportion of LASA-related drug selection errors involving TML-listed medications in a Malaysian public tertiary hospital.

Methods: A five-year retrospective cross-sectional study (2019–2023) was conducted based on pharmacy filling error data. Errors were categorised by type of errors, with drug selection errors further classified as LASA or non-LASA based on the institutional LASA and TML list. Descriptive analysis and Fisher’s exact test were performed to measure associations.

Results and Discussion: A total of 2,500 filling errors were identified (56.16 per 100,000 prescriptions), with wrong drug selection accounting for 75.8% (n=1,894) of cases. Only 8.1% (n=153) of selection errors were LASA-related, of which 98.0% involved medications included in the institutional TML list. LASA errors were significantly associated with medications included in the institutional Tall Man lettering list (p <0.001). In contrast, the majority of selection errors were non-LASA and involved mostly unrelated drug pairs, as well as drugs with varying strengths and dosage forms.

Conclusions: Most pharmacy filling errors were actually non-LASA errors and occurred beyond recognised LASA pairs. While TML remains relevant for targeted high-risk medications, the higher occurrence of non-LASA errors suggests that strategies focused on name differentiation alone may not address the key contributors of filling errors. Broader system-level safety strategies are therefore required to reduce filling errors meaningfully.