Handling of drug–drug interactions in clinical pharmacy practice

Abstract

Introduction Potential drug-drug interactions (DDI) are an important risk factor for adverse drug events (ADE). Automatic interaction check systems have been implemented in many hospitals but they are often not used by physicians due to “alert fatigue”. We tried to find out how often clinical pharmacists intervene because of DDI, and what are the reasons for this decision. Methods 1. All interventions of clinical pharmacists in our hospital in 2015, routinely documented with the GSASA-tool, were analysed for DDI. 2. A sample of medication profiles was checked for DDI (classes 1–4) using the ABDA database provided by emediat (integrated in our electronic prescribing tool) and compared to documented interventions of DDI. 3. Using a structured form, clinical pharmacists were asked after ward rounds, whether and why they did an interaction check, whether and why they intervened and whether the intervention was accepted by the physician. Results 1. One hundred and forty-six of 1170 (12%) interventions concerned DDI. Acceptance rate of DDI interventions was 93% compared to 87% of all interventions. 2. Twenty-seven out of 524 detected DDI (5%) were discussed during ward rounds. Most detected DDI (398) belonged to class 3. Intervention rate was 6.7% for class 1 DDI, 15.6% for class 2 DDI, 4.8% for class 3 DDI and 2.5% for class 4 DDI (lowest risk of DDI). 3. The evaluation and handling of DDI were observed in 83 patient charts involving 3 clinical pharmacists. In this sample (with potential observation bias), the intervention rate was 7% (21 of 313 DDI). In 24 cases, an interaction check was not performed, mainly because the interaction was known (15). Reasons for no intervention were: medication on demand (122), low DDI class or low risk of ADE (25), medication necessary/no alternative (9), other intervention more important (3), other such as discharge planned or no clinical relevance (131). Most frequent reasons for intervention were risk of toxic reaction (10) or of reduced effect (7). Seventeen (of 21) interventions were accepted by the physician in charge. Conclusions Interventions regarding possible DDI are low, because clinical pharmacists often judge DDI as not clinically relevant. Acceptance rate was high, possibly due to high clinical relevance. Physicians may have neither time nor enough pharmacologic knowledge to find out relevant DDI. Therefore, an automatic interaction check integrated in prescribing tools does not necessarily improve DDI detection. Clinical pharmacists can help to fill this gap, but should not forget others, equally important drug related problems.