Introduction
When a patient with cystic fibrosis (CF) is diagnosed with an exacerbation, the next step may involve inpatient hospital admission with a complex treatment regimen. Commonly more than four medications are prescribed, which can facilitate an increased number of drug-drug interactions.1
Drug-drug interactions occur when the effect of one drug is impacted by the concurrent administration of another.2 This causes either a favourable or unfavourable response. The favourable response increases the drug effectiveness; however, the potential unfavourable response is the toxic effects in the body.3 The mechanisms of drug-drug interactions are split into either pharmacokinetic or pharmacodynamic interactions.
In pharmacokinetic drug-drug interactions, the plasma concentration of the interacting drugs may be increased or decreased. For pharmacodynamic drug-drug interactions, the interacting drugs may produce synergistic or antagonistic effects.2,3 These respective drug-drug interactions can cause adverse drug effects.4
It has been well documented that drug-drug related interactions can cause severe adverse reactions resulting in serious harm to patients.4 Studies have shown adverse drug reactions increase mortality, morbidity and are responsible for longer in-patient hospital stays.5 The percentage of in-patient adverse drug reactions as a direct result from drug-drug interactions range from 3-5%.5 Factors increasing the risk of drug-drug interactions include: age, polypharmacy and co-morbidities – in particular cardiovascular disease.6,7
With the average age of survival for cystic fibrosis increasing, the risk of cardiovascular disease in turn has increased.8,9 It has been reported cardiovascular medications are commonly implicated in severe drug-drug related reactions.6,10 Therefore, knowledge of these potential drug-drug interactions is essential for improvement of medication safety, as this is an example of avoidable patient harm. However, drug-drug interactions between CF exacerbation medications and cardiovascular medications are not well reported.
This article was written to highlight the potential drug-drug interactions and adverse effects between commonly prescribed medications used for a cystic fibrosis exacerbation and cardiovascular medications.