Background Medical iatrogenesis represents a large proportion of avoidable direct and indirect health costs.

Purpose Evaluate quantitatively and qualitatively potential drug interactions by pharmaceutical assessment of hospitalised patients and outpatients’ prescriptions.

Material and methods A prospective observational monocentric one-day study including 590 prescriptions for (in/out) patients in a teaching hospital.

The analysis of prescription has been conducted with the help of the Vidal 2016 database and Theriaque.org (updated October 2017), the correlation of polypharmacy with drugs interactions by SPSS software v23.

Results Among the 590 prescriptions analysed corresponding to 1901 lines of prescription, an average of 3.23±1.918 (1, 11) of drugs per prescription and a median of 3.

Four-hundred and fifty-three prescriptions (76.8%) contained at least two drugs. We identified 128 prescriptions with at least one interaction (prevalence of 27.7%). A total of 165 interactions were counted with an average of 0.43 and a median of 0 interactions per prescription with at least two medications (0.8). A significant correlation has been demonstreted between number of drugs prescribed and number of interactions (r pearson=0.61 with p<0.05). There were three contraindications, 22 drug combinations discouraged (13.3%), 90 requiring precautions for use (54.5%) and 50 associations to consider (30.3%).

Different drug classes were incriminated in the occurrence of interactions: top of the list were cardiovascular drugs (45.5%) followed by drugs of the central nervous system (12.9%). The most specifically implicated drugs were captopril (10.8%), furosemide (6.3%) and acenocoumarol (4.8%).

Among the adverse effects that could be generated by these interactions, we note, first, cardiovascular effects at 37.4%, followed by metabolic disorders and nutrition with 18.4%. The most commonly observed adverse reactions were renal failure (26 cases) and orthostatic hypotension (23 cases).

This work allows us to establish a list of frequent drugs involved in the most frequent and serious drug interactions.

Conclusion Prevention of iatrogenicity is a complex problem. The pharmaceutical validation step is primordial in drug dispensing and requires a rich database of drug interactions that should be consulted in a systematic way. Following our study, an action plan was set up with the editing of a validation manual and a training schedule for pharmacists.

References and/or acknowledgements No conflict of interest.