Introduction: Dose dependent adverse drug reactions are often caused by prescribing errors ignoring upper dose limits. Thus, computerised physician order entry incorporating maximum recommended therapeutic doses (MRTDs) might reduce prescriptions of excessive doses. We evaluated the suitability of MRTD information as published in the Summary of Product Characteristics (SPC) (MRTD(SPC)) or by the US Food and Drug Administration (MRTD(FDA)) and the value of Defined Daily Doses (DDD, World Health Organisation) as knowledge bases for an alerting system.
Methods: In a large set of critical-dose drugs (N = 140) we compared MRTD(FDA) and DDD values with the corresponding German MRTD(SPC). We then retrospectively assessed a set of 633 electronically prescribed drugs (EPDs) issued at a university hospital and calculated prescription rates of excessive doses.
Results: MRTD(FDA) was similar to MRTD(SPC) in 37% (N = 140), higher in 32%, and lower in 31% of drugs. On average, available DDD values (N = 129) were 1.6 times lower than MRTD(SPC), with 64% being lower, 33% similar, and 3% larger than MRTD(SPC). Prescription rates of excessive doses according to MRTD(FDA) were 2.5-fold higher (6.1%) than according to MRTD(SPC) (2.5%) (p < 0.01). However, only one in four EPDs categorised as overdosed according to MRTD(FDA) exceeded MRTD(SPC), and MRTD(FDA) values were available only for 67% of all assessed EPDs.
Conclusion: Our study revealed a remarkable number of prescriptions with doses exceeding approved limits. Their prevention appears feasible but the choice of an appropriate database for MRTDs is essential, and differences between available information sources are large.