Background Look-alike packaging (LAP) designates similarity in labelling and packaging between two drugs. LAPs increase the risk of confusion while drug dispensing by technicians and pharmacists and drug administration by nurses, consequently leading to medication errors. No method exists to prospectively identify pairs of drugs and characteristics increasing confusion.

Objectives We propose a prospective identification method of LAPs in our hospital formulary, specifically on intravenous drugs. Our main objective was to validate our method of risk assessment. Other objectives were to evaluate the burden of LAP’s, to determine possible differences in results between different healthcare professionals (HCPs) and to identify risk factors of confusion inherent to drugs.

Method We selected 64 vials and 105 ampoules having a significant turnover in the pharmacy, allowing evaluation of risk for 2016 pairs of vials and 5460 pairs of ampoules. All pairs (primary packaging) were systematically observed by six HCPs independently (two nurses, two technicians and two pharmacists). If risk was identified by at least four HCPs, the pair was qualified as at “risk of confusion” (PairRC) and at “high risk of confusion” (PairHRC) if all HCPs perceived a risk. Inter-rater reliability was calculated (Cohen kappa test).

Results Inter-rater reliability varied from modest to good. A fifth of the vials and half the ampoules were identified at risk. No marked difference in number of pairs at risk was present amongst different professions, even though different pairs were identified by nurses. Risk factors of confusion are engravement and same manufacturer.

Conclusion Methods to identify risk of confusion prospectively should be implemented to propose preventive measures in order to reduce medication errors. Strategies for improvement may include over labelling, stockage in different places, educational strategies.

No conflict of interest.