What Do Medical Records Tell Us About Potentially Harmful Co-Prescribing?

Background: Previous efforts document drug-drug interactions in ambulatory care. Yet little is known about medical record documentation or clinical management when interacting medications are received. Methods: The study population was identified from the HMO Research Network's Centers for Education and Research on Therapeutics (n = 2,020,037). A random sub-sample of patients >= 18 years of age with drug coverage in 2000 initiating a co-dispensing for (1) warfarin with a nonsteroidal anti-inflammatory drug (n = 97), (2) digoxin with verapamil or diltiazem (n = 100), or (3) lovastatin/simvastatin with diltiazem or verapamil (n = 89) was identified. Results: The majority (63%-74%) of patients had documentation indicating receipt of both drugs during a single office visit. Documentation of risks and patient education was less common (<= 14%, with all corresponding upper bounds of the 95% CIs < 23%). Clinical management changes were more frequently documented, ranging from 64% (95% CI: 47-81%) for lovastatin/simvastatin patients to 79% (95% CI: 60-99%) for warfarin patients. Conclusions: The findings, although indicating that clinicians are likely aware of concomitant receipt of interacting medications, call into question the adequacy of medical record documentation as well as clinical management when interacting drugs are co-prescribed in the ambulatory setting.