Trimethoprim(continued)
▶Trimethoprimincreases the concentration ofantiepileptics
(fosphenytoin, phenytoin).oStudy
▶Antimalarials(pyrimethamine)increase the risk of side-effects
when given withtrimethoprim.rStudy
▶Trimethoprimis predicted to increase the anticoagulant effect
ofcoumarins.rStudy
▶Dapsoneincreases the exposure totrimethoprimand
trimethoprimincreases the exposure todapsone.rStudy
▶Trimethoprimincreases the concentration ofdigoxin.o
Study
▶Trimethoprimslightly increases the exposure tolamivudine.
oStudy
▶Trimethoprimis predicted to increase the risk of side-effects
when given withmethotrexate. Avoid.rTheoretical→Also
seeTABLE 2p. 847
▶Trimethoprimslightly increases the exposure torepaglinide.
Avoid or monitor blood glucose.oStudy
▶Rifampicindecreases the exposure totrimethoprim.o
Study
▶Trimethoprimis predicted to decrease the efficacy of
sapropterin.oTheoretical
Trimipramine→see tricyclic antidepressants
Tropicamide→seeTABLE 10p. 849 (antimuscarinics)
Trospium→seeTABLE 10p. 849 (antimuscarinics)
Tryptophan→seeTABLE 13p. 850 (serotonin syndrome)
▶Tryptophangreatly decreases the concentration oflevodopa.
oStudy
▶Tryptophanincreases the risk of side-effects when given with
monoamine-oxidase A and B inhibitors, irreversible.r
Anecdotal→Also seeTABLE 13p. 850
Typhoid vaccine, oral→see live vaccines
Ulipristal
▶Antiarrhythmics(dronedarone)are predicted to increase the
exposure toulipristal. Avoid if used for uterinefibroids.
oStudy
▶Antiepileptics(carbamazepine, eslicarbazepine, fosphenytoin,
oxcarbazepine, perampanel, phenobarbital, phenytoin,
primidone, rufinamide, topiramate)decrease the efficacy of
ulipristal. For FSRH guidance, seeContraceptives,
interactionsp. 497.rAnecdotal
▶Antifungals, azoles(fluconazole, isavuconazole, posaconazole)
are predicted to increase the exposure toulipristal. Avoid if
used for uterinefibroids.oStudy
▶Antifungals, azoles(itraconazole, ketoconazole, voriconazole)are
predicted to increase the exposure toulipristal. Avoid if used
for uterinefibroids.rStudy
▶Aprepitantdecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Bosentandecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Calcium channel blockers(diltiazem, verapamil)are predicted to
increase the exposure toulipristal. Avoid if used for uterine
fibroids.oStudy
▶Cobicistatis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.rStudy
▶Ulipristalis predicted to decrease the efficacy ofcombined
hormonal contraceptives. Avoid.rTheoretical
▶Crizotinibis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.oStudy
▶Ulipristalis predicted to decrease the efficacy ofdesogestrel.
Avoid.rTheoretical
▶Efavirenzdecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Enzalutamideis predicted to markedly decrease the exposure
toulipristal. Avoid and for 4 weeks after stoppingulipristal,
p. 507.rTheoretical
▶Ulipristalis predicted to decrease the efficacy ofetonogestrel.
Avoid.rTheoretical
▶Fosaprepitantdecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal▶Grapefruit juiceis predicted to increase the exposure to
ulipristal. Avoid if used for uterinefibroids.oTheoretical
▶Griseofulvinpotentially decreases the efficacy ofulipristal. For
FSRH guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶HIV-protease inhibitors(atazanavir, darunavir, fosamprenavir,
lopinavir, saquinavir, tipranavir)are predicted to increase the
exposure toulipristal. Avoid if used for uterinefibroids.r
Study
▶HIV-protease inhibitors(ritonavir)decrease the efficacy of
ulipristal. For FSRH guidance, seeContraceptives,
interactionsp. 497.rAnecdotal
▶Idelalisibis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.rStudy
▶Imatinibis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.oStudy
▶Ulipristalis predicted to decrease the efficacy of
levonorgestrel. Avoid.rTheoretical
▶Lumacaftoris predicted to decrease the efficacy ofulipristal.
Use additional contraceptive precautions.rTheoretical
▶Macrolides(clarithromycin)are predicted to increase the
exposure toulipristal. Avoid if used for uterinefibroids.r
Study
▶Macrolides(erythromycin)are predicted to increase the
exposure toulipristal. Avoid if used for uterinefibroids.
oStudy
▶Modafinildecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Netupitantis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.oStudy
▶Nevirapinedecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Nilotinibis predicted to increase the exposure toulipristal.
Avoid if used for uterinefibroids.oStudy
▶Ulipristalis predicted to decrease the efficacy of
norethisterone. Avoid.rTheoretical
▶Rifabutindecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
▶Rifampicindecreases the efficacy ofulipristal. For FSRH
guidance, seeContraceptives, interactionsp. 497.r
Anecdotal
Umeclidinium→seeTABLE 10p. 849 (antimuscarinics)
Urokinase→seeTABLE 3p. 847 (anticoagulant effects)
Ursodeoxycholic acid
▶Antacidsare predicted to decrease the absorption of
ursodeoxycholic acid. Separate administration by 2 hours.
oTheoretical
▶Ursodeoxycholic acidaffects the concentration ofciclosporin.
Use with caution and adjust dose.rAnecdotal
▶Fibratesare predicted to decrease the efficacy of
ursodeoxycholic acid. Avoid.rTheoretical
Ustekinumab→see monoclonal antibodies
Valaciclovir→seeTABLE 2p. 847 (nephrotoxicity)
▶Valacicloviris predicted to increase the exposure to
aminophylline.rAnecdotal
▶Mycophenolateis predicted to increase the risk of
haematological toxicity when given withvalaciclovir.o
Theoretical
▶Valacicloviris predicted to increase the exposure to
theophylline.rTheoretical
Valganciclovir→seeTABLE 15p. 850 (myelosuppression),TABLE 2
p. 847 (nephrotoxicity)
▶Valgancicloviris predicted to increase the risk of seizures when
given withcarbapenems(imipenem). Avoid.rAnecdotal
▶Valgancicloviris predicted to increase the exposure to
didanosine.oStudy
▶Mycophenolateis predicted to increase the risk of
haematological toxicity when given withvalganciclovir.
oTheoretical→Also seeTABLE 15p. 850
Valproate→see antiepileptics
Valsartan→see angiotensin-II receptor antagonists1006 Trimethoprim—Valsartan BNFC 2018 – 2019
Interactions|Appendix 1A1