Background Reconciliation of discrepancies in the patient's treatment may improve the quality of healthcare in a population susceptible to drug errors.

Purpose To analyse differences detected in home treatment after hospital discharge for polymedicated patients (typically ≥6 drugs in their treatment) over 64 years of age.

Materials and methods Cross-sectional study of patients undergoing treatment, over 64 years of age, admitted to the internal medicine ward in the period March to July of 2011. The authors reviewed the medicines documented in the electronic medical records prior to admission, on discharge as well as on the day of home visits (at least 3 weeks after discharge). During the visits, the patient, family and/or carer were interviewed in order to find out the patient's current medicines and to detect possible discrepancies. Discrepancies were considered to be present when there were unexplained differences between the medicines documented in the electronic medical record and those actually taken by the patient.

Results A total of 52 patients were included in this study and our findings showed that the 92.3% displayed at least one discrepancy in their usual chronic medicines between what was prescribed and taken. The different types of discrepancies detected were as follows: 49.2% of the patients were noted as not taking a drug they had previously been taking (omission), 53.6% were still taking a drug that had been suspended (commission), 73.0% had a difference in dose, route and/or frequency of administration, in 28.9% no substitution had been performed and 11.8% had duplication.

Conclusions Discrepancies between what is prescribed and taken in the chronic treatment of polymedicated patients over 64 years old are a common event, especially those relating to dose, route and/or frequency of administration.