require the reduction of the
dexamethasone dose when co-
administered with an NK 1 RA
have already been discussed.
Other strong CYP3A4 inducers
or inhibitors may also alter
the pharmacokinetics of
corticosteroids. Although
the manufacturer of
dexamethasone
states that dose-
adjustments may
also be required
in this case,
there is no clear
recommendation
on how to adjust
the dose. Antacids
and activated
charcoal may reduce
the bioavailability of
corticosteroids and their
co-adiministration should be
separated by at least 2 h. 25
Dexamethasone is associated
with a variety of pharmacodynamic
interactions. Nevertheless,
when short-term courses of
dexamethasone are used, as is the
case in the management of CINV,
the likelihood of adverse events
related to DDIs is probably lower
compared with more frequent use.
Those most commonly seen in
practice relate to the concomitant
use of corticosteroids with non-
steroidal antiinflammatory drugs
and anticoagulants, where the
risk of bleeding is increased and
patients should be monitored.
Concomitant use with antidiabetics
(insulin, sulfonylureas, metformin)
might lead to hyperglycaemia and
patients’ glucose concentrations
should be monitored more
frequently. The concomitant use
of corticosteroids with potassium-
depleting agents (that is,
diuretics) may cause
hypokalaemia and
patients’ potassium
levels should be
monitored. Also,
corticosteroids
may antagonise
the effect of
antihypertensives,
which may require
dose adjustment.
Short treatment
courses with smaller
corticosteroid doses are
probably not a contraindication
to vaccines. 26
Conclusions
Antiemetic drugs used to
prevent CINV are associated
with numerous DDIs. Usually,
monitoring of AEs or laboratory
parameters is sufficient but in
some cases avoidance of DDIs,
dose-adjustment (corticosteroids,
olanzapine), additional measures
(contraception) or the use of
another drug within the same class
(palonosetron vs other 5-HT 3 RAs)
might be necessary. Administration
of the most appropriate antiemetic
prophylaxis for the specific patient
is at the physicians’ discretion and
responsibility.
hospitalpharmacyeurope.com | 2019 | 79