slightly increases the exposure to roflumilast.

Study

▶ H2 receptor antagonists potentially decrease the exposure to

sofosbuvir. Adjust dose, see ledipasvir with sofosbuvir p. 628,

sofosbuvir with velpatasvir p. 629, and sofosbuvir with

velpatasvir and voxilaprevir p. 630.oStudy

▶ Cimetidine slightly increases the exposure to SSRIs (citalopram,

escitalopram). Adjust dose.oStudy

▶ Cimetidine slightly increases the exposure to SSRIs (paroxetine,

sertraline).oStudy

▶ Cimetidine is predicted to increase the risk of toxicity when

given with tegafur.rTheoretical

▶ Teriflunomide is predicted to increase the exposure to H2

receptor antagonists (cimetidine, famotidine).oStudy

▶ Cimetidine increases the concentration of theophylline. Adjust

dose.rStudy

▶ Cimetidine

o

increases the exposure to tricyclic antidepressants.

Study

▶ H2 receptor antagonists are predicted to decrease the

concentration of velpatasvir. Adjust dose, see sofosbuvir with

velpatasvir p. 629.oStudy

▶ Cimetidine slightly increases the exposure to venlafaxine.n

Study

▶ Cimetidine slightly increases the exposure to zolmitriptan.

Adjust zolmitriptan dose, p. 482.nStudy

Haloperidol → see TABLE 8 p. 1376 (hypotension), TABLE 9 p. 1377 (QTinterval prolongation), TABLE 11 p. 1377 (CNS depressant effects),

TABLE 10 p. 1377 (antimuscarinics)

FOOD AND LIFESTYLE Dose adjustment might be necessary if

smoking started or stopped during treatment.

▶ Antiepileptics (carbamazepine, fosphenytoin, phenobarbital,

phenytoin, primidone) decrease the concentration of

haloperidol. Adjust dose.oStudy → Also see TABLE 11

p. 1377

▶ Haloperidol potentially increases the risk of overheating and

dehydration when given with antiepileptics (zonisamide). Avoid

in children.rTheoretical

▶ Antifungals, azoles (itraconazole) increase the concentration of

haloperidol.oStudy

▶ Haloperidol is predicted to decrease the effects of dopamine

receptor agonists. Avoid.oTheoretical → Also see TABLE 8

p. 1376 → Also see TABLE 9 p. 1377 → Also see TABLE 10 p. 1377

▶ Enzalutamide decreases the concentration of haloperidol.

Adjust dose.oStudy

▶ Haloperidol potentially opposes the effects of glycerol

phenylbutyrate.oTheoretical

▶ Haloperidol is predicted to decrease the antihypertensive

effects of

Theoretical

guanethidine

→ Also see TABLE 8

. Monitor and adjust dose.

p. 1376

o ▶ HIV-protease inhibitors (ritonavir) are predicted to increase the

exposure to haloperidol.rTheoretical

▶ Haloperidol decreases the effects of levodopa.rStudy →

Also see TABLE 8 p. 1376

▶ Mitotane decreases the concentration of haloperidol. Adjust

dose.oStudy

▶ Rifampicin decreases the concentration of haloperidol. Adjust

dose.oStudy

▶ Haloperidol potentially decreases the effects of sodium

phenylbutyrate.oAnecdotal

▶ SSRIs (fluoxetine) increase the concentration of haloperidol.

Adjust dose.oAnecdotal

▶ SSRIs (fluvoxamine) increase the concentration of haloperidol.

Adjust dose.oStudy

▶ Venlafaxine

r

slightly increases the exposure to haloperidol.

Study → Also see TABLE 9 p. 1377 → Also see TABLE 11 p. 1377

Heparin (unfractionated) → see TABLE 16 p. 1379 (increased serum

potassium), TABLE 3 p. 1375 (anticoagulant effects)

▶ Ranibizumab increases the risk of bleeding events when given

with heparin (unfractionated).rTheoretical

Hepatitis B immunoglobulin → see immunoglobulins

HIV-protease inhibitors → see TABLE 9 p. 1377 (QT-interval

prolongation)

atazanavir. darunavir. fosamprenavir. lopinavir.ritonavir. saquinavir.tipranavir.

▶ Caution on concurrent use of atazanavir, lopinavir with

ritonavir, and ritonavir with drugs that prolong the PR

interval.

▶ Concurrent use of saquinavir with drugs that prolong the

PR interval is contra-indicated.

▶ Caution with concurrent use of tipranavir with drugs that

increase risk of bleeding.

▶ Tipranavir

r

slightly decreases the exposure to abacavir. Avoid.

Study

▶ HIV-protease inhibitors are predicted to increase the exposure

Study

to abemaciclib. Avoid or adjust abemaciclib dose, p. 967.r

▶ HIV-protease inhibitors (lopinavir, ritonavir, saquinavir) are

predicted to increase the exposure to afatinib. Separate

administration by 12 hours.oStudy

▶ Ritonavir

o

is predicted to decrease the exposure to agomelatine.

Theoretical

▶ Ritonavir

Study

decreases the exposure to albendazole.o ▶ HIV-protease inhibitors are predicted to markedly increase the

Study

exposure to aldosterone antagonists (eplerenone). Avoid.r

▶ HIV-protease inhibitors (ritonavir, saquinavir) are predicted to

increase the exposure to aliskiren.oTheoretical

▶ HIV-protease inhibitors increase the exposure to almotriptan.

nStudy

▶ HIV-protease inhibitors are predicted to moderately increase

the exposure to alpha blockers (alfuzosin, tamsulosin). Use with

caution or avoid.oStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to alpha blockers (doxazosin).oStudy

▶ HIV-protease inhibitors moderately increase the exposure to

alprazolam. Avoid.oStudy

▶ HIV-protease inhibitors (ritonavir, tipranavir) are predicted to

increase the exposure to amfetamines.rTheoretical

▶ Ritonavir decreases the exposure to aminophylline. Adjust

dose.oStudy

▶ Ritonavir is predicted to decrease the exposure to anaesthetics,

local (ropivacaine).oTheoretical

▶ Antacids are predicted to decrease the absorption of

atazanavir. Atazanavir should be taken 2 hours before or

1 hour after antacids.rTheoretical

BNF 78 H2 receptor antagonists — HIV-protease inhibitors 1463

Interactions | Appendix 1

A1

HIV-protease inhibitors (continued)

▶ Antacids are predicted to decrease the absorption of

tipranavir. Separate administration by 2 hours.oStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to antiarrhythmics (amiodarone). Avoid.rTheoretical → Also

see TABLE 9 p. 1377

▶ HIV-protease inhibitors are predicted to increase the exposure

to antiarrhythmics (disopyramide).rTheoretical → Also see

TABLE 9 p. 1377

▶ HIV-protease inhibitors very markedly increase the exposure to

antiarrhythmics (dronedarone). Avoid.rStudy → Also see

TABLE 9 p. 1377

▶ Ritonavir is predicted to increase the exposure to

antiarrhythmics

r

(flecainide). Avoid or monitor side effects.

Theoretical

▶ HIV-protease inhibitors are predicted to increase the exposure

to antiarrhythmics (lidocaine). Avoid.rStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to

r

antiarrhythmics (propafenone). Monitor and adjust dose.

Study

▶ HIV-protease inhibitors are predicted to increase the exposure

to anticholinesterases, centrally acting (galantamine). Monitor

and adjust dose.oStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to antiepileptics (carbamazepine) and antiepileptics

(carbamazepine) are predicted to decrease the exposure to

HIV-protease inhibitors

Theoretical

. Monitor and adjust dose.r

▶ HIV-protease inhibitors are predicted to affect the exposure to

antiepileptics (fosphenytoin, phenytoin) and antiepileptics

(fosphenytoin, phenytoin) decrease the concentration of HIVprotease inhibitors.rTheoretical

▶ Ritonavir slightly decreases the exposure to antiepileptics

(lamotrigine).rStudy

▶ HIV-protease inhibitors are predicted to very slightly increase

the exposure to antiepileptics (perampanel).nStudy

▶ HIV-protease inhibitors are predicted to affect the

concentration of antiepileptics (phenobarbital, primidone) and

antiepileptics (phenobarbital, primidone) are predicted to

decrease the concentration of

Theoretical

HIV-protease inhibitors.r

▶ Ritonavir is predicted to decrease the concentration of

antiepileptics (valproate).rAnecdotal

▶ Antifungals, azoles (fluconazole) slightly increase the exposure

to tipranavir. Avoid or adjust dose.oStudy

▶ Antifungals, azoles (miconazole) are predicted to increase the

concentration of HIV-protease inhibitors. Use with caution and

adjust dose.oTheoretical

▶ Antifungals, azoles (posaconazole) are predicted to increase the

exposure to HIV-protease inhibitors.oStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to antifungals, azoles (isavuconazole). Avoid or monitor side

effects.rStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to antifungals, azoles (itraconazole). Use with caution and

adjust dose.rStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to antifungals, azoles (ketoconazole). Use with caution and

adjust dose.oStudy

▶ HIV-protease inhibitors are predicted to affect the exposure to

antifungals, azoles (voriconazole) and antifungals, azoles

(voriconazole) potentially affect the exposure to HIV-protease

inhibitors.rStudy → Also see TABLE 9 p. 1377

▶ HIV-protease inhibitors are predicted to increase the exposure

to antihistamines, non-sedating (mizolastine). Avoid.rStudy

▶ HIV-protease inhibitors are predicted to increase the exposure

to

Study

antihistamines, non-sedating (rupatadine). Avoid.o ▶ HIV-protease inhibitors decrease the exposure to antimalarials

(atovaquone). Avoid if boosted with ritonavir.oStudy

▶ HIV-protease inhibitors are predicted to increase the

concentration of antimalarials (piperaquine).rTheoretical

▶ HIV-protease inhibitors are predicted to decrease the exposure

to antimalarials (proguanil). Avoid.oStudy

▶ HIV-protease inhibitors are predicted to affect the exposure to

antimalarials (quinine).rStudy → Also see TABLE 9 p. 1377

▶ HIV-protease inhibitors are predicted to increase the exposure

to apalutamide.nStudy → Also see TABLE 9 p. 1377

▶ Ritonavir is predicted to increase the exposure to apixaban.

Avoid.rTheoretical

▶ HIV-protease inhibitors are predicted to markedly increase the

exposure to aprepitant.oStudy

▶ HIV-protease inhibitors are predicted to slightly increase the

exposure to

o