Exposure to potentially inappropriate drugs and drug-drug interactions in elderly nursing home residents in Helsinki, Finland: a cross-sectional study.

BACKGROUND AND OBJECTIVE: Multiple drug use is common among old, frail nursing home residents who are, as a consequence, susceptible to adverse effects and drug interactions. This study uses the updated Beers criteria for potentially inappropriate drug (PID) use in older adults to determine the extent and nature of PIDs in older nursing home residents in Helsinki, Finland. The study also uses the Swedish, Finnish, INteraction X-referencing (SFINX) interaction database to assess the possibility of clinically significant class D ("clinically significant interaction, and the combination should be avoided") drug-drug interactions (DDIs) in the same population.

METHODS: This study is a cross-sectional assessment of all nursing home residents aged > or = 65 years in Helsinki. The residents' demographic information and medical data were collected from medical charts in February 2003.

RESULTS: Of all nursing home residents in Helsinki, 82% (n = 1987) were eligible for analysis. Their mean age was 83.7 (SD 7.7) years, 80.7% were female and 69.5% were diagnosed with dementia. The mean number of drugs given on a regular basis per resident was 7.9 (SD 3.6) per day. Of the study population, 34.9% regularly used at least one PID. Residents taking PIDs were more likely to be taking psychotropic medication and to be taking nine or more drugs daily, and less likely to have a diagnosis of dementia, than patients not taking PIDs. The three most prevalent PIDs were: (i) short-acting benzodiazepines in greater than recommended doses (13.9% of all residents), of which temazepam >15 mg/day was the most commonly used agent and, indeed, the most common PID (taken by 13.5% of all residents); (ii) hydroxyzine (7.1%); and (iii) nitrofurantoin (6.3%). Together, these three PIDs accounted for 76.9% of all PID use. Of all residents, 4.8% were susceptible to a clinically significant DDI. The most common potential DDIs were related to the use of potassium-sparing diuretics, carbamazepine and codeine. Compared with residents not exposed to potential DDIs, residents exposed to potential DDIs were more likely to be younger, to have a prior history of stroke, to be taking psychotropics, to be taking nine or more drugs daily and to be taking PIDs.

CONCLUSION: Use of PIDs is very common among nursing home residents, and this increases the likelihood of DDIs. Monitoring patients for PID use and potential drug interactions could increase the quality of prescribing.