BNF for Children 2011-2012

718 Appendix 1: Interactions BNFC 2011–2012Appendix 1: InteractionsPerindopril see ACE InhibitorsPerphenazine see AntipsychoticsPethidine see Opioid AnalgesicsPhenazocine see Opioid AnalgesicsPhenelzine see MAOIsPhenindioneNote Change in patient’s clinical condition particularlyassociated with liver disease, intercurrent illness, or drugadministration, necessitates more frequent testing. Majorchanges in diet (especially involving salads and vegetables)and in alcohol consumption may also affect anticoagulantcontrol. Alcohol: anticoagulant control with phenindione maybe affected by major changes in consumption of.alcohol. Anabolic Steroids: anticoagulant effect of phenindioneenhanced by .anabolic steroids. Analgesics: anticoagulant effect of phenindione possiblyenhanced by .NSAIDs; increased risk ofhaemorrhage when anticoagulants given with intravenous.diclofenac (avoid concomitant use, includinglow-dose heparins); increased risk of haemorrhagewhen anticoagulants given with .ketorolac (avoidconcomitant use, including low-dose heparins);increased risk of bleeding when phenindione givenwith .aspirin (due to antiplatelet effect). Anti-arrhythmics: metabolism of phenindione inhibitedby .amiodarone (enhanced anticoagulant effect). Antibacterials: experience in anticoagulant clinicssuggests that INR possibly altered when phenindioneis given with .neomycin (given for local action ongut); anticoagulant effect of phenindione possiblyenhanced by levofloxacin and .tetracyclines; studieshave failed to demonstrate an interaction withphenindione, but common experience in anticoagulantclinics is that INR can be altered by acourse of broad-spectrum penicillins such as ampicillin;metabolism of phenindione possibly inhibitedby sulfonamides. Antivirals: anticoagulant effect of phenindione possiblyenhanced by .ritonavir. Clopidogrel: anticoagulant effect of phenindioneenhanced due to antiplatelet action of .clopidogrelCorticosteroids: anticoagulant effect of phenindionemay be enhanced or reduced by corticosteroids. Dipyridamole: anticoagulant effect of phenindioneenhanced due to antiplatelet action of .dipyridamole. Enteral Foods: anticoagulant effect of phenindioneantagonised by vitamin K (present in some .enteralfeeds )Iloprost: increased risk of bleeding when phenindionegiven with iloprost. Lipid-regulating Drugs: anticoagulant effect of phenindionemay be enhanced or reduced by.colestyramine; anticoagulant effect of phenindionepossibly enhanced by .rosuvastatin; anticoagulanteffect of phenindione enhanced by .fibrates. Oestrogens: anticoagulant effect of phenindioneantagonised by .oestrogensPrasugrel: possible increased risk of bleeding whenphenindione given with prasugrel. Progestogens: anticoagulant effect of phenindioneantagonised by .progestogens. Testolactone: anticoagulant effect of phenindioneenhanced by .testolactone. Testosterone: anticoagulant effect of phenindioneenhanced by .testosterone. Thyroid Hormones: anticoagulant effect of phenindioneenhanced by .thyroid hormones. Vitamins: anticoagulant effect of phenindione antagonisedby .vitamin KPhenobarbitalNote Primidone interactions as for phenobarbitalAlcohol: increased sedative effect when phenobarbitalgiven with alcoholAnalgesics: phenobarbital reduces plasma concentrationof methadone. Anti-arrhythmics: phenobarbital accelerates metabolismof disopyramide (reduced plasma concentra-Phenobarbital. Anti-arrhythmics (continued)tion); phenobarbital possibly reduces plasmaconcentration of .dronedarone—avoid concomitantuse. Antibacterials: phenobarbital accelerates metabolismof metronidazole (reduced effect); phenobarbitalpossibly reduces plasma concentration of rifampicin;phenobarbital accelerates metabolism of doxycycline(reduced plasma concentration); phenobarbital possiblyaccelerates metabolism of .chloramphenicol(reduced plasma concentration); phenobarbitalreduces plasma concentration of .telithromycin(avoid during and for 2 weeks after phenobarbital). Anticoagulants: phenobarbital accelerates metabolismof .coumarins (reduced anticoagulant effect). Antidepressants: phenobarbital reduces plasma concentrationof paroxetine; phenobarbital acceleratesmetabolism of .mianserin (reduced plasma concentration);anticonvulsant effect of antiepileptics possiblyantagonised by MAOIs and .tricyclic-relatedantidepressants (convulsive threshold lowered); anticonvulsanteffect of antiepileptics antagonised by.SSRIs and .tricyclics (convulsive thresholdlowered); avoid concomitant use of antiepilepticswith .St John’s wort; phenobarbital possibly acceleratesmetabolism of .tricyclics (reduced plasmaconcentration). Antiepileptics: plasma concentration of phenobarbitalpossibly increased by carbamazepine; phenobarbitalpossibly reduces plasma concentration of ethosuximide,rufinamide and topiramate; phenobarbitalreduces plasma concentration of lamotrigine,tiagabine and zonisamide; plasma concentration ofphenobarbital increased by oxcarbazepine, alsoplasma concentration of an active metabolite ofoxcarbazepine reduced; plasma concentration ofphenobarbital often increased by phenytoin, plasmaconcentration of phenytoin often reduced but may beincreased; plasma concentration of phenobarbitalincreased by .stiripentol; plasma concentration ofphenobarbital increased by valproate (also plasmaconcentration of valproate reduced). Antifungals: phenobarbital possibly reduces plasmaconcentration of itraconazole and .posaconazole;phenobarbital possibly reduces plasma concentrationof .voriconazole—avoid concomitant use; phenobarbitalreduces absorption of griseofulvin (reducedeffect). Antimalarials: possible increased risk of convulsionswhen antiepileptics given with chloroquine andhydroxychloroquine; anticonvulsant effect of antiepilepticsantagonised by .mefloquine. Antipsychotics: anticonvulsant effect of antiepilepticsantagonised by .antipsychotics (convulsive thresholdlowered); phenobarbital accelerates metabolism ofhaloperidol (reduced plasma concentration); plasmaconcentration of both drugs reduced when phenobarbitalgiven with chlorpromazine; phenobarbitalpossibly reduces plasma concentration of.aripiprazole—increase dose of aripiprazole; phenobarbitalpossibly reduces plasma concentration ofclozapine. Antivirals: phenobarbital possibly reduces plasmaconcentration of abacavir, darunavir, fosamprenavir,.indinavir, .lopinavir, .nelfinavir and .saquinavir;avoidance of phenobarbital advised by manufacturerof etravirineAnxiolytics and Hypnotics: phenobarbital oftenreduces plasma concentration of clonazepamAprepitant: phenobarbital possibly reduces plasmaconcentration of aprepitantBeta-blockers: phenobarbital possibly reduces plasmaconcentration of propranolol. Calcium-channel Blockers: phenobarbital probablyreduces effects of .calcium-channel blockers; avoidanceof phenobarbital advised by manufacturer ofisradipine; avoidance of phenobarbital advised by