BNF for Children 2011-2012

366 6.2.1 Thyroid hormones BNFC 2011–20126 Endocrine systemthyroiditis (lymphadenoid goitre). Neonatal hypothyroidismrequires prompt treatment to facilitate normaldevelopment.Levothyroxine sodium (thyroxine sodium) is the treatmentof choice for maintenance therapy.Doses for congenital hypothyroidism and juvenile myxoedemashould be titrated according to clinicalresponse, growth assessment, and measurement ofplasma thyroxine and thyroid-stimulating hormone concentrations.In congenital hypothyroidism higher initialdoses may normalise metabolism more quickly, withassociated beneficial effects on mental development.Liothyronine sodium has a similar action to levothyroxinebut is more rapidly metabolised and has a morerapid effect; 20–25 micrograms is equivalent to approximately100 micrograms of levothyroxine. Its effectsdevelop after a few hours and disappear within 24 to48 hours of discontinuing treatment. It may be used insevere hypothyroid states when a rapid response isdesired.Liothyronine by intravenous injection is the treatment ofchoice in hypothyroid coma. Adjunctive therapyincludes intravenous fluids, hydrocortisone, and treatmentof infection; assisted ventilation is often required.LEVOTHYROXINE SODIUM(Thyroxine sodium)Cautions panhypopituitarism or predisposition toadrenal insufficiency (initiate corticosteroid therapybefore starting levothyroxine); cardiac disorders(monitor ECG; start at low dose and carefully titrate);long-standing hypothyroidism, diabetes insipidus,diabetes mellitus (dose of antidiabetic drugs includinginsulin may need to be increased); interactions:Appendix 1 (thyroid hormones)Pregnancy monitor maternal serum-thyrotrophinconcentration—levothyroxine may cross the placentaand excessive maternal concentration can be detrimentalto fetusBreast-feeding amount too small to affect tests forneonatal hypothyroidismSide-effects usually at excessive dosage includediarrhoea, vomiting; anginal pain, arrhythmias, palpitation,tachycardia, benign intracranial hypertension;tremor, restlessness, excitability, insomnia,headache, flushing, sweating, fever, heat intolerance,weight loss, nervousness; craniosynostosis and prematureclosure of epiphyses; menstrual irregularities;eosinophilia, liver dysfunction; muscle cramps, muscularweakness; transient hair loss; hypersensitivityreactions including rash, pruritus and oedema alsoreportedIndication and doseHypothyroidismNote Levothyroxine equivalent to 100 micrograms/m 2 /day can be used as a guide to the requirements inchildren. By mouthNeonate initially 10–15 micrograms/kg once daily(max. 50 micrograms daily), adjusted in steps of5 micrograms/kg every 2 weeks or as necessary;usual maintenance dose 20–50 micrograms dailyChild 1 month–2 years initially 5 micrograms/kgonce daily (max. 50 micrograms daily) adjusted insteps of 10–25 micrograms daily every 2–4 weeksuntil metabolism normalised; usual maintenancedose 25–75 micrograms dailyChild 2–12 years initially 50 micrograms oncedaily adjusted in steps of 25 micrograms dailyevery 2–4 weeks until metabolism normalised;usual maintenance dose 75–100 micrograms dailyChild 12–18 years initially 50 micrograms oncedaily adjusted in steps of 25–50 micrograms dailyevery 3–4 weeks until metabolism normalised;usual maintenance dose 100–200 microgramsdailyLevothyroxine (Non-proprietary) ATablets, levothyroxine sodium 25 micrograms, netprice 28-tab pack = £2.22; 50 micrograms, 28-tab pack= £1.09; 100 micrograms, 28-tab pack = £1.09Brands include Eltroxin cOral solution, levothyroxine sodium 25 micrograms/5 mL, net price 100 mL = £42.75; 50 micrograms/5 mL, 100 mL = £44.90; 100 micrograms/5 mL,100 mL = £52.75Brands include Evotrox c (sugar-free)Note All strengths of levothyroxine oral solution by Almusand branded as Evotrox c , have been reformulated (August2010) leading to an increase in potency of approximately10%; the manufacturer advises that the recommended dosehas not changed, but recommends increased monitoring ofpatients on these preparations as dose adjustments may benecessaryLIOTHYRONINE SODIUM(L-Tri-iodothyronine sodium)Cautions severe and prolonged hypothyroidism (initiatecorticosteroid therapy in adrenal insufficiency);cardiac disorders (monitor ECG; start at low dose andcarefully titrate); diabetes insipidus, diabetes mellitus(dose of antidiabetic drugs including insulin may needto be increased); interactions: Appendix 1 (thyroidhormones)Pregnancy does not cross the placenta in significantamounts; monitor maternal thyroid function tests—dosage adjustment may be necessaryBreast-feeding amount too small to affect tests forneonatal hypothyroidismSide-effects usually at excessive dosage includediarrhoea; anginal pain, arrhythmias, palpitation,tachycardia; restlessness, excitability, headache,flushing, sweating, weight loss; muscle cramps,muscle weaknessLicensed use unlicensed for use in childrenIndication and doseSee also notes aboveHypothyroidism. By mouthChild 12–18 years initially 10–20 microgramsdaily gradually increased to 60 micrograms daily in2–3 divided doses. By slow intravenous injection(replacement for oral levothyroxine)Convert daily levothyroxine dose to liothyronine(see notes above for approximate equivalence) andgive in 2–3 divided doses, adjusted according toresponse