Use of ATC to describe duplicate medications in primary care prescriptions

We aimed to demonstrate the suitability of the Anatomical Therapeutic Chemical Classification (ATC) to describe duplicate drugs and duplicate drug classes in prescription data and describe the pattern of duplicates from public and private primary care clinics of Kuala Lumpur, Malaysia. We analyzed prescription data year 2005 from all 14 public clinics in Kuala Lumpur with 12,157 prescriptions, and a sample of 188 private clinics with 25,612 prescriptions. As ATC Level 5 code represents the molecule and Level 4 represents the pharmacological subgroup, we used repetitions of codes in the same prescription to describe duplicate drugs or duplicate drug classes and compared them between the public and private clinics. At Level 4 ATC, prescriptions with duplicates drug classes were 1.46% of all prescriptions in private and 0.04% in public clinics. At Level 5 ATC, prescriptions with duplicate drugs were 1.81% for private and 0.95% for public clinics. In private clinics at Level 5, 73.3% of prescriptions with duplicates involved systemic combination drugs; at Level 4, 40.3% involved systemic combination drugs. In the public sector at Level 5, 95.7% of prescriptions with duplicates involved topical products. Repetitions of the same ATC codes were mostly useful to describe duplicate medications; however, we recommend avoid using ATC codes for tropical products for this purpose due to ambiguity. Combination products were often involved in duplicate prescribing; redesign of these products might improve prescribing quality. Duplicates occurred more often in private clinics than public clinics in Malaysia.