Drug information centre queries and responses about drug interactions over 10 years-A descriptive analysis

Many people are treated with ≥1 drug, implying that risks of drug interactions need to be considered. The aim of this study was to describe drug interaction queries from healthcare professionals to a drug information centre in Sweden over 10 years focusing on drugs frequently asked about and the advice provided. Advice was recorded in mutually exclusive groups: Avoid, Adjust dose, Separate intake, Vigilance or No problem. For queries with Avoid, Adjust dose or Separate intake advice, alerts were extracted from an interaction database (Janusmed). Of 4335 queries to the centre in 2008-2017, 589 (14%) concerned interactions. Most were posed by physicians (91%) and concerned a specific patient (83%) before treatment initiation (76%). Sertraline, warfarin and methotrexate were the most frequently asked about, whereas queries about cyclophosphamide and rifampicine occurred most often in relation to the number of exposed patients. Advice provided in 557 (95%) replies comprised Avoid: n = 85 (15%), Adjust dose: n = 57 (10%), Separate intake: n = 17 (3%), Vigilance: n = 235 (42%) or No problem: n = 163 (29%). In all, 113 (71%) of 159 queries with Avoid/Adjust dose/Separate intake advice elicited an action alert on Janusmed, whereas 31 (20%) did not result in any alert at all. Summarized, seven in ten replies from the drug information centre recommended an explicit drug treatment action, regarding either specific prescribing aspects, for instance dose adjustments, or active follow-up including monitoring potential adverse reactions and/or laboratory results. Readily accessible decision support regarding drug interactions often provides relevant action alerts, but cannot be solely relied on.