BNF for Children 2011-2012

BNFC 2011–2012 2.8.2 Oral anticoagulants 119dried prothrombin complex unavailable, fresh frozenplasma 15 mL/kg can be given but is lesseffective). INR > 8.0, no bleeding or minor bleeding—stopwarfarin and give phytomenadione (vitamin K 1 )2.5–5 mg by mouth using the intravenous preparationorally [unlicensed use], or 0.5–1 mg by slowintravenous injection (if complete reversal required5–10 mg by slow intravenous injection); repeat doseof phytomenadione if INR still too high after 24hours; restart warfarin when INR < 5.0. INR 5.0–8.0, no bleeding—stop warfarin; minorbleeding—stop warfarin and give phytomenadione(vitamin K 1 ) 1–2.5 mg by mouth using the intravenouspreparation orally [unlicensed use]; restartwarfarin when INR < 5.0. Unexpected bleeding at therapeutic levels—alwaysinvestigate possibility of underlying cause e.g.unsuspected renal or gastro-intestinal tract pathologyPregnancy Oral anticoagulants are teratogenic andshould not be given in the first trimester of pregnancy.Adolescents at risk of pregnancy should be warned ofthis danger since stopping warfarin before the sixthweek of gestation may largely avoid the risk of fetalabnormality. Oral anticoagulants cross the placenta withrisk of congenital malformations, and placental, fetal, orneonatal haemorrhage, especially during the last fewweeks of pregnancy and at delivery. Therefore, if at allpossible, oral anticoagulants should be avoided inpregnancy, especially in the first and third trimesters.Difficult decisions may have to be made, particularly inthose with prosthetic heart valves or with a history ofrecurrent venous thrombosis, pulmonary embolism, oratrial fibrillation.Babies of mothers taking warfarin at the time of deliveryneed to be offered immediate prophylaxis with at least100 micrograms/kg of intramuscular phytomenadione(vitamin K 1 ), see section 9.6.6.Dietary differences Infant formula is supplementedwith vitamin K, which makes formula-fed infants resistantto warfarin; they may therefore need higher doses.In contrast breast milk contains low concentrations ofvitamin K making breast-fed infants more sensitive towarfarin.Treatment booklets Anticoagulant treatment bookletsshould be issued to children or their carers, and areavailable for distribution to local healthcare professionalsfrom Health Authorities and from:3M Security Printing and Systems LimitedGorse StreetChaddertonOldham, OL9 9QHTel: 0845 610 1112nhsforms@spsl.uk.comThese booklets include advice for children or theircarers on anticoagulant treatment, an alert card to becarried by the patient at all times, and a section forrecording of INR results and dosage information. Electroniccopies are also available at www.npsa.nhs.uk/nrls/alerts-and-directives/alerts/anticoagulant.WARFARIN SODIUMCautions see notes above; also recent surgery; recentischaemic stroke; history of gastro-intestinal bleeding;peptic ulcer; concomitant use of drugs that increaserisk of bleeding; bacterial endocarditis (increased riskof bleeding; use only if warfarin otherwise indicated);avoid cranberry juice; interactions: Appendix 1(warfarin)Contra-indications haemorrhagic stroke; significantbleeding; avoid use within 48 hours postpartumHepatic impairment avoid in severe impairment,especially if prothrombin time already prolongedRenal impairment use with caution (avoid in severeimpairment)Pregnancy see notes aboveBreast-feeding not present in milk in significantamounts; no evidence of harm; see also notes aboveSide-effects haemorrhage—see notes above; alsonausea, vomiting, diarrhoea, jaundice, hepatic dysfunction,pancreatitis, pyrexia, alopecia, purpura,rash, ‘purple toes’, skin necrosis (increased risk inpatients with protein C or protein S deficiency)Licensed use not licensed for use in childrenIndication and doseTreatment and prophylaxis of thrombotic episodes. By mouthNeonate (under specialist advice) 200 micrograms/kgas a single dose on first day, reduced to100 micrograms/kg once daily for following 3 days(but if INR still below 1.4 use 200 micrograms/kgonce daily, or if INR above 3 use 50 micrograms/kg once daily, if INR above 3.5 omit dose); thenadjusted according to INR, usual maintenance100–300 micrograms/kg once daily (may need upto 400 micrograms/kg once daily especially ifbottle fed—see notes above)Child 1 month–18 years 200 micrograms/kg(max. 10 mg) as a single dose on first day, reducedto 100 micrograms/kg (max. 5 mg) once daily forfollowing 3 days (but if INR still below 1.4 use200 micrograms/kg (max. 10 mg) once daily, or ifINR above 3 use 50 micrograms/kg (max. 2.5 mg)once daily, or if INR above 3.5 omit dose); thenadjusted according to INR, usual maintenance100–300 micrograms/kg once daily (may need upto 400 micrograms/kg once daily especially ifbottle fed—see notes above)Note Induction dose may need to be altered according tocondition (e.g. abnormal liver function tests, cardiacfailure), concomitant interacting drugs, and if baselineINR above 1.3Warfarin (Non-proprietary) ATablets, warfarin sodium 500 micrograms (white), netprice 28-tab pack = £1.49; 1 mg (brown), 28-tab pack= 93p; 3 mg (blue), 28-tab pack = 95p; 5 mg (pink), 28-tab pack = £1.03. Label: 10, anticoagulant cardBrands include Marevan cOral suspension, warfarin sodium 5 mg/5 mL, netprice 150-mL = £90.00. Label: 10, anticoagulant cardExtemporaneous formulations available seeExtemporaneous Preparations, p. 62 Cardiovascular system