Preventable and non-preventable adverse drug events in hospitalized patients

OBJECTIVE: To analyse the prevalence of preventable adverse drug events (pADEs) and non-preventable adverse drug reactions (ADRs) as well as the determinants of both pADEs and ADRs. METHODS: Adverse events experienced by patients admitted to two Dutch hospitals with functioning computerized physician order entry (CPOE) systems were prospectively identified through chart review. For both pADEs and non-preventable ADRs a causal relationship between adverse events and patients' drugs was established using the simplified Yale algorithm. RESULTS: pADEs and non-preventable ADRs were experienced by 349 (58%) patients, of whom 307 (88%) had non-preventable ADRs. Multi-morbidity (adjusted odds ratio [ORadj] 1.90 and 1.28 respectively), length of stay (OR adj 1.13 and 1.11), admission to the geriatric ward (ORadj 7.78 and 3.82) and number of medication orders (ORadj 1.25 and 1.13) were significantly associated with pADEs and ADRs. Admission to the gastroenterology/rheumatology ward (ORadj 0.22 and 0.40) was inversely related to both pADEs and ADRs. Other determinants for ADRs only were female sex (ORadj 1.77) and use of drugs affecting the nervous system (ORadj 1.83). Age was a significant determinant for pADEs only (ORadj 1.07). CONCLUSIONS: More than half of the patients admitted to the hospitals are harmed by drugs, of which most are non-serious, non-preventable ADRs. Determinants of both pADEs and ADRs overlap to a large extent. Our results imply the need for signalling early potential adverse events during the normal use of drugs in multimorbid patients or those in geriatric wards. Subsequent therapeutic interventions may improve their well-being more than focusing on errors in the medication process only.