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.