The majority of hospitalised patients have drug-related problems: results from a prospective study in general hospitals

Objective: To describe the frequency and types of drug-related problems (DRPs) in hospitalised patients, and to identify risk factors for DRPs and the drugs most frequently causing them. Methods: From May to December 2002, 827 patients from six internal medicine and two rheumatology departments in five hospitals in Norway were included in this study. We recorded demographic data, drugs used, relevant medical history, laboratory data and clinical/ pharmacological risk factors, i.e. reduced renal function, reduced liver function, heart failure, diabetes, compliance problems, drugs with a narrow therapeutic index and drug allergy. DRPs were documented after reviewing medical records and participation in multidisciplinary team discussions. An independent quality assessment team retrospectively assessed the DRPs in a randomly selected number of the study population. Results: Of the patients, 81% had DRPs, and an average of 2.1 clinically relevant DRPs was recorded per patient. The DRPs most frequently recorded were dose-related problems (35.1% of the patients) followed by need for laboratory tests (21.6%), non-optimal drugs (21.4%), need for additional drugs (19.7%), unnecessary drugs (16.7%) and medical chart errors (16.3%). The patients used an average of 4.6 drugs at admission. A multivariate analysis showed that the number of drugs at admission and the number of clinical/pharmacological risk factors were both independent risk factors for the occurrence of DRPs, whereas age and gender were not. The drugs most frequently causing a DRP were warfarin, digitoxin and prednisolone, with calculated risk ratios 0.48, 0.42 and 0.26, respectively. The drug groups causing most DRPs were B01A-antithrombotic agents, M01A-non-steroidal anti-inflammatory agents, N02A-opioids and C09A-angiotensin converting enzyme inhibitors, with risk ratios of 0.22, 0.49, 0.21 and 0.35, respectively. Conclusions: The majority of hospitalised patients in our study had DRPs. The number of drugs used and the number of clinical/pharmacological risk factors significantly and independently influenced the risk for DRPs. Procedures for identification of, and intervention on, actual and potential DRPs, along with awareness of drugs carrying a high risk for DRPs, are important elements of drug therapy and may contribute to diminishing drug-related morbidity and mortality.