BNF for Children 2011-2012

720 Appendix 1: Interactions BNFC 2011–2012Appendix 1: InteractionsPhenytoin. Antipsychotics (continued)possibly increased or decreased by chlorpromazine;phenytoin possibly reduces plasma concentrationof .aripiprazole—increase dose ofaripiprazole; phenytoin accelerates metabolism ofclozapine and quetiapine (reduced plasma concentration). Antivirals: phenytoin possibly reduces plasma concentrationof abacavir, darunavir, lopinavir andsaquinavir; avoidance of phenytoin advised bymanufacturer of etravirine; phenytoin possiblyreduces plasma concentration of .indinavir, alsoplasma concentration of phenytoin possiblyincreased; plasma concentration of phenytoinreduced by nelfinavir; phenytoin possibly reducesplasma concentration of ritonavir, also plasma concentrationof phenytoin possibly affected; plasmaconcentration of phenytoin increased or decreasedby zidovudineAnxiolytics and Hypnotics: phenytoin often reducesplasma concentration of clonazepam; plasma concentrationof phenytoin increased or decreased bydiazepam; plasma concentration of phenytoin possiblyincreased or decreased by benzodiazepinesAprepitant: phenytoin possibly reduces plasma concentrationof aprepitantBupropion: phenytoin reduces plasma concentration ofbupropion. Calcium-channel Blockers: phenytoin reduces effectsof felodipine and verapamil; avoidance of phenytoinadvised by manufacturer of isradipine; avoidance ofphenytoin advised by manufacturer of nimodipine(plasma concentration of nimodipine possiblyreduced); plasma concentration of phenytoinincreased by .diltiazem but also effect of diltiazemreducedCardiac Glycosides: phenytoin possibly reducesplasma concentration of digoxin. Ciclosporin: phenytoin accelerates metabolism of.ciclosporin (reduced plasma concentration). Corticosteroids: phenytoin accelerates metabolism of.corticosteroids (reduced effect). Cytotoxics: phenytoin possibly reduces plasma concentrationof busulfan and etoposide; metabolism ofphenytoin possibly inhibited by fluorouracil(increased risk of toxicity); phenytoin increases antifolateeffect of methotrexate; plasma concentrationof phenytoin possibly reduced by cisplatin; avoidanceof phenytoin advised by manufacturer of gefitinib and.lapatinib; phenytoin reduces plasma concentrationof .imatinib—avoid concomitant use; phenytoinreduces plasma concentration of irinotecan and itsactive metaboliteDiazoxide: plasma concentration of phenytoin reducedby diazoxide, also effect of diazoxide may be reduced. Disulfiram: metabolism of phenytoin inhibited by.disulfiram (increased risk of toxicity). Diuretics: plasma concentration of phenytoin possiblyincreased by .acetazolamide; phenytoin antagoniseseffects of furosemide; phenytoin reduces plasmaconcentration of .eplerenone—avoid concomitantuse; increased risk of osteomalacia when phenytoingiven with carbonic anhydrase inhibitorsDopaminergics: phenytoin possibly reduces effects oflevodopaEnteral Foods: absorption of phenytoin possiblyreduced by enteral feedsFolates: plasma concentration of phenytoin possiblyreduced by folatesHormone Antagonists: phenytoin possibly acceleratesmetabolism of toremifene5HT 3 Antagonists: phenytoin accelerates metabolismof ondansetron (reduced effect)Leflunomide: plasma concentration of phenytoinpossibly increased by leflunomideLevamisole: plasma concentration of phenytoin possiblyincreased by levamisolePhenytoin (continued)Lipid-regulating Drugs: absorption of phenytoin possiblyreduced by colesevelam; combination ofphenytoin with fluvastatin may increase plasmaconcentration of either drug (or both)Lithium: neurotoxicity may occur when phenytoingiven with lithium without increased plasma concentrationof lithiumModafinil: plasma concentration of phenytoin possiblyincreased by modafinilMuscle Relaxants: phenytoin antagonises musclerelaxant effect of non-depolarising muscle relaxants(accelerated recovery from neuromuscular blockade). Oestrogens: phenytoin accelerates metabolism of.oestrogens (reduced contraceptive effect—seep. 398). Orlistat: possible increased risk of convulsions whenantiepileptics given with .orlistat. Progestogens: phenytoin accelerates metabolism of.progestogens (reduced contraceptive effect—seep. 398). Sulfinpyrazone: plasma concentration of phenytoinincreased by .sulfinpyrazoneSympathomimetics: plasma concentration of phenytoinincreased by methylphenidateTacrolimus: phenytoin reduces plasma concentrationof tacrolimus, also plasma concentration of phenytoinpossibly increased. Theophylline: plasma concentration of both drugsreduced when phenytoin given with .theophyllineThyroid Hormones: phenytoin accelerates metabolismof thyroid hormones (may increase requirements inhypothyroidism), also plasma concentration ofphenytoin possibly increasedTibolone: phenytoin accelerates metabolism of tibolone. Ulcer-healing Drugs: metabolism of phenytoin inhibitedby .cimetidine (increased plasma concentration);effects of phenytoin enhanced by .esomeprazole;effects of phenytoin possibly enhanced by omeprazole;absorption of phenytoin reduced by.sucralfate. Ulipristal: avoidance of phenytoin advised by manufacturerof .ulipristal (contraceptive effect of ulipristalpossibly reduced)Vaccines: effects of phenytoin enhanced by influenzavaccineVitamins: phenytoin possibly increases requirementsfor vitamin DPholcodineAntidepressants: manufacturer of pholcodine advisesavoid for 2 weeks after stopping MAOIsPhosphodiesterase Type-3 Inhibitors. Anagrelide: avoidance of enoximone and milrinoneadvised by manufacturer of .anagrelidePhysostigmine see ParasympathomimeticsPilocarpine see ParasympathomimeticsPimozide see AntipsychoticsPindolol see Beta-blockersPioglitazone see AntidiabeticsPiperacillin see PenicillinsPipotiazine see AntipsychoticsPiroxicam see NSAIDsPivmecillinam see PenicillinsPizotifenAdrenergic Neurone Blockers: pizotifen antagoniseshypotensive effect of adrenergic neurone blockersPlatinum Compounds. Aldesleukin: avoidance of cisplatin advised by manufacturerof .aldesleukin. Antibacterials: increased risk of nephrotoxicity andpossibly of ototoxicity when platinum compoundsgiven with .aminoglycosides or .polymyxins;increased risk of nephrotoxicity and ototoxicity whenplatinum compounds given with capreomycin;increased risk of nephrotoxicity and possibly ofototoxicity when cisplatin given with vancomycin