▶Fibrates(bezafibrate, ciprofibrate)increase the risk of
rhabdomyolysis when given withstatins(simvastatin). Adjust
simvastatindose,p. 134.rStudy
▶Gemfibrozilincreases the risk of rhabdomyolysis when given
withstatins. Avoid.rAnecdotal
▶Fibratesare predicted to increase the risk of hypoglycaemia
when given withsulfonylureas.oTheoretical
▶Gemfibrozilis predicted to increase the concentration of
taxanes(paclitaxel).rAnecdotal
▶Fibratesare predicted to decrease the efficacy of
ursodeoxycholic acid. Avoid.rTheoretical
Fidaxomicin
▶Antiarrhythmics(amiodarone, dronedarone)are predicted to
increase the exposure tofidaxomicin. Avoid.oStudy
▶Antifungals, azoles(itraconazole, ketoconazole)are predicted to
increase the exposure tofidaxomicin. Avoid.oStudy
▶Calcium channel blockers(verapamil)are predicted to increase
the exposure tofidaxomicin. Avoid.oStudy
▶Ciclosporinis predicted to increase the exposure to
fidaxomicin. Avoid.oStudy
▶HIV-protease inhibitors(lopinavir, ritonavir, saquinavir)are
predicted to increase the exposure tofidaxomicin. Avoid.
oStudy
▶Lapatinibis predicted to increase the exposure tofidaxomicin.
Avoid.oStudy
▶Macrolidesare predicted to increase the exposure to
fidaxomicin. Avoid.oStudy
▶Ranolazineis predicted to increase the exposure to
fidaxomicin. Avoid.oStudy
▶Vemurafenibis predicted to increase the exposure to
fidaxomicin. Avoid.oStudy
Fingolimod→seeTABLE 6p. 848 (bradycardia),TABLE 9p. 849 (QT-
interval prolongation)
▶Antiepileptics(carbamazepine, fosphenytoin, phenobarbital,
phenytoin, primidone)are predicted to decrease the exposure
tofingolimod.oStudy
▶Calcium channel blockers(diltiazem, verapamil)are predicted to
increase the exposure tofingolimod. Avoid.o
Theoretical→Also seeTABLE 6p. 848
▶Enzalutamideis predicted to decrease the exposure to
fingolimod.oStudy
▶Live vaccinesare predicted to increase the risk of generalised
infection (possibly life-threatening) when given with
fingolimod. Public Health England advises avoid (refer to
Green Book).rTheoretical
▶Mitotaneis predicted to decrease the exposure tofingolimod.
oStudy
▶Rifampicinis predicted to decrease the exposure tofingolimod.
oStudy
▶St John’s Wortis predicted to decrease the exposure to
fingolimod. Avoid.oTheoretical
Flavoxate→seeTABLE 10p. 849 (antimuscarinics)
Flecainide→see antiarrhythmics
Flucloxacillin→see penicillins
Fluconazole→see antifungals, azoles
Flucytosine
▶Amphotericinincreases the risk of toxicity when given with
flucytosine.rStudy
▶Cytarabinedecreases the concentration offlucytosine. Avoid.
rStudy
Fludarabine→seeTABLE 15p. 850 (myelosuppression)
▶Live vaccinesare predicted to increase the risk of generalised
infection (possibly life-threatening) when given with
fludarabine. Public Health England advises avoid (refer to
Green Book).rTheoretical
▶Fludarabineincreases the risk of pulmonary toxicity when
given withpentostatin. Avoid.rStudy→Also seeTABLE 15
p. 850
Fludrocortisone→see corticosteroids
Fluocinolone
ROUTE-SPECIFIC INFORMATIONWith intravitreal use in adults:
caution with concurrent administration of anticoagulant or
antiplatelet drugs (higher incidence of conjunctival
haemorrhage).Fluorouracil→seeTABLE 15p. 850 (myelosuppression),TABLE 5p. 847
(thromboembolism)
ROUTE-SPECIFIC INFORMATIONSince systemic absorption can
follow topical application, the possibility of interactions
should be borne in mind.
▶Fluorouracilincreases the concentration ofantiepileptics
(fosphenytoin, phenytoin). Monitor concentration and adjust
dose.rAnecdotal
▶Fluorouracilincreases the anticoagulant effect ofcoumarins.
rAnecdotal
▶Folates(folic acid)are predicted to increase the risk of toxicity
when given withfluorouracil. Avoid.rTheoretical
▶Folates(folinic acid)are predicted to increase the risk of
toxicity when given withfluorouracil. Monitor and adjust
dose.rTheoretical
▶H 2 receptor antagonists(cimetidine)slightly increase the
exposure tofluorouracil.rStudy
▶Live vaccinesare predicted to increase the risk of generalised
infection (possibly life-threatening) when given with
fluorouracil. Public Health England advises avoid (refer to
Green Book).rTheoretical
▶Metronidazoleincreases the risk of toxicity when given with
fluorouracil.rStudy
Fluoxetine→see SSRIs
Flupentixol→seeTABLE 8p. 848 (hypotension),TABLE 11p. 849 (CNS
depressant effects)
▶Flupentixolis predicted to decrease the effects ofdopamine
receptor agonists. Avoid.oTheoretical→Also seeTABLE 8
p. 848
▶Flupentixoldecreases the effects oflevodopa. Avoid or monitor
worsening parkinsonian symptoms.rTheoretical→Also
seeTABLE 8p. 848
Fluphenazine→see phenothiazines
Flurazepam→seeTABLE 11p. 849 (CNS depressant effects)
▶HIV-protease inhibitors(ritonavir)are predicted to increase the
exposure toflurazepam. Avoid.oTheoretical
Flurbiprofen→see NSAIDs
Fluticasone→see corticosteroids
Fluvastatin→see statins
Fluvoxamine→see SSRIs
Folates
folic acid.folinic acid.levofolinic acid..
▶Folatesare predicted to decrease the concentration of
antiepileptics(fosphenytoin, phenobarbital, phenytoin,
primidone). Monitor concentration and adjust dose.r
Study
▶Folatesare predicted to increase the risk of toxicity when
given withcapecitabine.rAnecdotal
▶Folic acidis predicted to increase the risk of toxicity when
given withfluorouracil. Avoid.rTheoretical
▶Folinic acidis predicted to increase the risk of toxicity when
given withfluorouracil. Monitor and adjust dose.r
Theoretical
▶Folatesare predicted to alter the effects ofraltitrexed. Avoid.
oStudy
▶Sulfasalazineis predicted to decrease the absorption offolates.
oStudy
▶Folatesare predicted to increase the risk of toxicity when
given withtegafur.rTheoretical
Folic acid→see folates
Folinic acid→see folates
Fondaparinux→seeTABLE 3p. 847 (anticoagulant effects)
Formoterol→see beta 2 agonists
Fosamprenavir→see HIV-protease inhibitors
Fosaprepitant
▶Antiepileptics(carbamazepine, fosphenytoin, phenobarbital,
phenytoin, primidone)are predicted to decrease the exposure
tofosaprepitant. Avoid.oTheoretical
▶Antifungals, azoles(itraconazole, ketoconazole, voriconazole)are
predicted to increase the exposure tofosaprepitant.o
Theoretical
▶Fosaprepitantis predicted to increase the exposure to
bosutinib.rTheoreticalBNFC 2018 – 2019 Fibrates—Fosaprepitant 923
Interactions|Appendix 1A1