BNF for Children 2011-2012

722 Appendix 1: Interactions BNFC 2011–2012Appendix 1: InteractionsProgesterone see ProgestogensProgestogensNote Interactions of combined oral contraceptives may alsoapply to combined contraceptive patches and vaginal rings,see p. 398. For further information on interactions of oralprogestogen-only contraceptives, see also p. 403; parenteralprogestogen-only contraceptives, see also p. 404; the intrauterineprogestogen-only device, see also p. 405; hormonalemergency contraception, see also p. 408. Antibacterials: plasma concentration of dienogestincreased by erythromycin; metabolism of progestogensaccelerated by .rifamycins (reduced contraceptiveeffect—see p. 398). Anticoagulants: progestogens may enhance or reduceanticoagulant effect of coumarins; progestogensantagonise anticoagulant effect of .phenindione. Antidepressants: contraceptive effect of progestogensreduced by .St John’s wort (avoid concomitant use)Antidiabetics: progestogens antagonise hypoglycaemiceffect of antidiabetics. Antiepileptics: metabolism of progestogens acceleratedby .carbamazepine, .eslicarbazepine,.oxcarbazepine, .phenobarbital, .phenytoin,.rufinamide and .topiramate (reduced contraceptiveeffect—see p. 398); desogestrel possibly increasesplasma concentration of lamotrigineAntifungals: progestogens possibly increase plasmaconcentration of voriconazole; anecdotal reports ofcontraceptive failure and menstrual irregularitieswhen progestogens given with griseofulvin; occasionalreports of breakthrough bleeding when progestogens(used for contraception) given withterbinafine. Antivirals: plasma concentration of norethisteroneincreased by atazanavir; contraceptive effect ofprogestogens possibly reduced by .efavirenz andnelfinavir; metabolism of progestogens acceleratedby .nevirapine (reduced contraceptive effect—seep. 398). Aprepitant: possible contraceptive failure of hormonalcontraceptives containing progestogens when givenwith .aprepitant (alternative contraception recommended). Bosentan: possible contraceptive failure of hormonalcontraceptives containing progestogens when givenwith .bosentan (alternative contraception recommended)Ciclosporin: progestogens possibly increase plasmaconcentration of ciclosporinDiuretics: risk of hyperkalaemia when drospirenonegiven with potassium-sparing diuretics and aldosteroneantagonists (monitor serum potassium duringfirst cycle). Dopaminergics: progestogens increase plasma concentrationof .selegiline—manufacturer of selegilineadvises avoid concomitant useLipid-regulating Drugs: plasma concentration of norethisteroneincreased by atorvastatin; plasma concentrationof active metabolite of norgestimateincreased by rosuvastatin; plasma concentration ofnorgestrel increased by rosuvastatinMuscle Relaxants: progestogens possibly increaseplasma concentration of tizanidine (increased risk oftoxicity)Sitaxentan: plasma concentration of progestogensincreased by sitaxentanSugammadex: plasma concentration of progestogenspossibly reduced by sugammadex—manufacturer ofsugammadex advises additional contraceptive precautions. Ulipristal: contraceptive effect of progestogens possiblyreduced by .ulipristalProguanilAntacids: absorption of proguanil reduced by oralmagnesium salts (as magnesium trisilicate)Anticoagulants: isolated reports that proguanil mayenhance anticoagulant effect of warfarin. Antimalarials: avoidance of antimalarials advised bymanufacturer of .artemether/lumefantrine;Proguanil. Antimalarials (continued)increased antifolate effect when proguanil givenwith pyrimethamineHistamine: avoidance of antimalarials advised bymanufacturer of histamineVaccines: antimalarials inactivate oral typhoidvaccine—see p. 620Promazine see AntipsychoticsPromethazine see AntihistaminesPropafenoneAnaesthetics, Local: increased myocardial depressionwhen anti-arrhythmics given with bupivacaine, levobupivacaine,prilocaine or ropivacaine. Anti-arrhythmics: increased myocardial depressionwhen anti-arrhythmics given with other .antiarrhythmics. Antibacterials: metabolism of propafenone acceleratedby .rifampicin (reduced effect). Anticoagulants: propafenone enhances anticoagulanteffect of .coumarins. Antidepressants: metabolism of propafenone possiblyinhibited by paroxetine (increased risk of toxicity);increased risk of arrhythmias when propafenonegiven with .tricyclics. Antihistamines: increased risk of ventricular arrhythmiaswhen propafenone given with .mizolastine—avoid concomitant use. Antipsychotics: increased risk of ventricular arrhythmiaswhen anti-arrhythmics that prolong the QTinterval given with .antipsychotics that prolong theQT interval. Antivirals: plasma concentration of propafenone possiblyincreased by .fosamprenavir (increased risk ofventricular arrhythmias—avoid concomitant use);plasma concentration of propafenone increased by.ritonavir (increased risk of ventricular arrhythmias—avoidconcomitant use); increased risk ofventricular arrhythmias when propafenone givenwith .saquinavir—avoid concomitant use. Beta-blockers: increased myocardial depression whenanti-arrhythmics given with .beta-blockers; propafenoneincreases plasma concentration ofmetoprolol and propranolol. Cardiac Glycosides: propafenone increases plasmaconcentration of .digoxin (halve dose of digoxin)Ciclosporin: propafenone possibly increases plasmaconcentration of ciclosporinParasympathomimetics: propafenone possibly antagoniseseffects of neostigmine and pyridostigmineTheophylline: propafenone increases plasma concentrationof theophylline. Ulcer-healing Drugs: plasma concentration of propafenoneincreased by .cimetidinePropantheline see AntimuscarinicsPropiverine see AntimuscarinicsPropofol see Anaesthetics, GeneralPropranolol see Beta-blockersProstaglandinsACE Inhibitors: enhanced hypotensive effect whenalprostadil given with ACE inhibitorsAdrenergic Neurone Blockers: enhanced hypotensiveeffect when alprostadil given with adrenergicneurone blockersAlpha-blockers: enhanced hypotensive effect whenalprostadil given with alpha-blockersAngiotensin-II Receptor Antagonists: enhancedhypotensive effect when alprostadil given withangiotensin-II receptor antagonistsBeta-blockers: enhanced hypotensive effect whenalprostadil given with beta-blockersCalcium-channel Blockers: enhanced hypotensiveeffect when alprostadil given with calcium-channelblockersClonidine: enhanced hypotensive effect when alprostadilgiven with clonidineDiazoxide: enhanced hypotensive effect when alprostadilgiven with diazoxide