A cross-sectional survey of patient drug prescriptions on two elderly psychiatric wards was carried out to estimate the potential of drug–drug interactions. Two standardised databases, British National Formulary (BNF; British Medical Association & Royal Pharmaceutical Society of Great Britain, 2007) and Upto Date (www.uptodate.com/), were employed.
A majority (96%) of drug prescriptions in our study could potentially cause drug–drug interactions. Most patients were on multiple drugs (on average eight drugs per patient). There was poor concordance between the two databases: BNF picked up fewer cases of potential drug–drug interactions than Upto Date (43 v. 152 instances) and they also estimated the potential for hazardousness differently.
Polypharmacy is common in elderly psychiatric patients and this increases the possibility of a drug–drug interaction. Estimating the risk of interactions depends on a sound knowledge in therapeutics and/or referring to a standardised source of information. the results of this study question the concordance of two well-referenced databases.
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