BNF for Children 2011-2012

BNFC 2011–2012 Appendix 1: Interactions 715Oestrogens (continued)Beta-blockers: oestrogens antagonise hypotensiveeffect of beta-blockers. Bosentan: possible contraceptive failure of hormonalcontraceptives containing oestrogens when givenwith .bosentan (alternative contraception recommended)Calcium-channel Blockers: oestrogens antagonisehypotensive effect of calcium-channel blockersCiclosporin: oestrogens possibly increase plasma concentrationof ciclosporinClonidine: oestrogens antagonise hypotensive effect ofclonidineCorticosteroids: oral contraceptives containingoestrogens increase plasma concentration of corticosteroidsDiuretics: oestrogens antagonise diuretic effect ofdiuretics. Dopaminergics: oestrogens increase plasma concentrationof ropinirole; oestrogens increase plasmaconcentration of .selegiline—manufacturer of selegilineadvises avoid concomitant useLipid-regulating Drugs: absorption of ethinylestradiolreduced by colesevelam; plasma concentration ofethinylestradiol increased by atorvastatin and rosuvastatinMethyldopa: oestrogens antagonise hypotensive effectof methyldopa. Modafinil: metabolism of oestrogens accelerated by.modafinil (reduced contraceptive effect—seep. 398)Moxonidine: oestrogens antagonise hypotensive effectof moxonidineMuscle Relaxants: oestrogens possibly increaseplasma concentration of tizanidine (increased risk oftoxicity)Nitrates: oestrogens antagonise hypotensive effect ofnitratesSitaxentan: plasma concentration of oestrogensincreased by sitaxentanSomatropin: oestrogens (when used as oral replacementtherapy) may increase dose requirements ofsomatropinTacrolimus: ethinylestradiol possibly increases plasmaconcentration of tacrolimusTheophylline: oestrogens increase plasma concentrationof theophylline (consider reducing dose oftheophylline)Thyroid Hormones: oestrogens may increase requirementsfor thyroid hormones in hypothyroidismVasodilator Antihypertensives: oestrogens antagonisehypotensive effect of hydralazine, minoxidil andsodium nitroprussideOestrogens, conjugated see OestrogensOfloxacin see QuinolonesOlanzapine see AntipsychoticsOlmesartan see Angiotensin-II Receptor AntagonistsOlsalazine see AminosalicylatesOmeprazole see Proton Pump InhibitorsOndansetron see 5HT 3 AntagonistsOpioid AnalgesicsAlcohol: enhanced hypotensive and sedative effectswhen opioid analgesics given with alcoholAnaesthetics, General: fentanyl inhibits metabolism ofetomidate (consider reducing dose of etomidate);opioid analgesics possibly enhance effects of intravenousgeneral anaesthetics and volatile liquidgeneral anaestheticsAntibacterials: plasma concentration of alfentanilincreased by erythromycin; avoidance of premedicationwith opioid analgesics advised by manufacturerof ciprofloxacin (reduced plasma concentrationof ciprofloxacin) when ciprofloxacin used for surgicalprophylaxis; metabolism of alfentanil, codeine,fentanyl, methadone and morphine accelerated byrifampicin (reduced effect); metabolism of oxycodonepossibly accelerated by rifampicin; metabolism ofoxycodone inhibited by telithromycinOpioid Analgesics (continued). Anticoagulants: tramadol enhances anticoagulanteffect of .coumarins. Antidepressants: plasma concentration of methadonepossibly increased by fluoxetine, fluvoxamine,paroxetine and sertraline; possible increased serotonergiceffects when pethidine or tramadol given withduloxetine; possible increased serotonergic effectswhen tramadol given with mirtazapine or venlafaxine;CNS excitation or depression (hypertension orhypotension) when pethidine given with .MAOIs—avoid concomitant use and for 2 weeks after stoppingMAOIs; possible CNS excitation or depression(hypertension or hypotension) when opioid analgesicsgiven with .MAOIs—some manufacturersadvise avoid concomitant use and for 2 weeks afterstopping MAOIs; possible increased serotonergiceffects and increased risk of convulsions whentramadol given with .MAOIs—some manufacturersadvise avoid concomitant use and for 2 weeks afterstopping MAOIs; possible CNS excitation or depression(hypertension or hypotension) when opioidanalgesics given with .moclobemide—manufacturerof moclobemide advises consider reducing dose ofopioid analgesics; possible CNS excitation ordepression (hypertension or hypotension) whendextromethorphan or pethidine given with.moclobemide—avoid concomitant use; increasedrisk of CNS toxicity when tramadol given with.SSRIs or .tricyclics; plasma concentration ofmethadone possibly reduced by St John’s wort;sedative effects possibly increased when opioidanalgesics given with tricyclics. Antiepileptics: effects of tramadol reduced by carbamazepine;plasma concentration of methadonereduced by carbamazepine and phenobarbital;dextropropoxyphene enhances effects of.carbamazepine; morphine increases bioavailabilityof gabapentin; metabolism of methadone acceleratedby phenytoin (reduced effect and risk of withdrawaleffects). Antifungals: metabolism of buprenorphine inhibited by.ketoconazole (reduce dose of buprenorphine);metabolism of alfentanil inhibited by fluconazole (riskof prolonged or delayed respiratory depression);metabolism of alfentanil possibly inhibited by itraconazole;plasma concentration of alfentanil andmethadone increased by .voriconazole (considerreducing dose of alfentanil and methadone); plasmaconcentration of oxycodone increased by.voriconazole; plasma concentration of fentanylpossibly increased by .triazoles. Antihistamines: sedative effects possibly increasedwhen opioid analgesics given with .sedating antihistaminesAntimuscarinics: possible increased risk of antimuscarinicside-effects when codeine given withantimuscarinics. Antipsychotics: enhanced hypotensive and sedativeeffects when opioid analgesics given with antipsychotics;increased risk of ventricular arrhythmiaswhen methadone given with .antipsychotics thatprolong the QT interval; increased risk of convulsionswhen tramadol given with antipsychotics; increasedrisk of ventricular arrhythmias when methadonegiven with .amisulpride—avoid concomitant use. Antivirals: plasma concentration of methadone possiblyreduced by abacavir and nevirapine; methadonepossibly reduces plasma concentration of didanosine;plasma concentration of methadone reduced byefavirenz, fosamprenavir, nelfinavir and ritonavir;plasma concentration of dextropropoxypheneincreased by .ritonavir (risk of toxicity)—avoidconcomitant use; plasma concentration of buprenorphinepossibly increased by ritonavir; plasmaconcentration of alfentanil and fentanyl increased by.ritonavir; plasma concentration of pethidinereduced by .ritonavir, but plasma concentration oftoxic pethidine metabolite increased (avoid conco-Appendix 1: Interactions