Background Drug dispensing errors are a common reason for medicines errors in hospitals, although they don’t usually reach the patient. Different situations contribute to their appearance, such as the availability of drugs from the same supplier, similarity in names, physical closeness, etc.

Purpose To analyse the drugs most commonly involved in medicines errors during the dispensing process in a tertiary hospital.

To study the possible causes thereof.

Materials and methods Since 2011, medicines errors detected during the drug dispensing process after prescription-transcription in hospitalised patients have been recorded using an internal pharmacy database.

Data collected: drug involved, pharmaceutical form, prescription frequency, person notifying, whether the report was correct and possible reason.

We extracted errors reported from 571 hospital beds over 2 years (July/2011–June/2013) from the database and analysed each one.

Results 1049 dispensing errors were detected and included in the database, all notified by staff nurses. 81.7% were confirmed to be errors. In 14 cases, the medicines box was empty (because of movements in patient census). In 4 cases, different drugs were involved.

Pharmaceutical forms detected were oral (79.24%), injectable (14.71%), inhalational (4.3%) and topical (1.66%).

11.86% of the reported errors corresponded to High-Alert Medicines from the ISMP (Institute For Safe Medication Practices) list. The most frequent were heparins (7.11%), which accounted for 4.12% of the total of prescriptions. Insulin and anticoagulant drugs only had 4 and 6 errors, respectively.

Other common drugs involved and the frequency of their prescription compared to the total of prescriptions were: furosemide (5.93%-3.14%), omeprazole (4.86%-4.65%), amoxicillin/clavulanic acid (2.97%-2%), ipratropium (2.25%-0.82%), piperacillin/tazobactam (1.78%-1.76%), methylprednisolone (1.78%-1.11%), carvedilol (1.66%-1.01), amlodipine (1.42%-0.76%), atorvastatin (1.42%-0.53%) and levothyroxine (1.42%-0.33%).

For 9 of these drugs, there were similar presentations with different doses and/or physical proximity.

Conclusion The main drugs involved in dispensing errors are drugs for which there are various doses and frequent prescriptions (such as heparins) or those most frequently prescribed (such as omeprazole and furosemide), specially oral drugs. The number of errors with High-Alert Medicines was low.

It’s important to know the distribution/availability of similar drugs to establish corrective measures for procurement and distribution and to minimise errors.

No conflict of interest.