lPREGNANCYLevothyroxine may cross the placenta.
Excessive or insufficient maternal thyroid hormones can
be detrimental to fetus.
Dose adjustmentsLevothyroxine requirement may
increase during pregnancy.
MonitoringAssess maternal thyroid function before
conception (if possible), at diagnosis of pregnancy, at
antenatal booking, during both the second and third
trimesters, and after delivery (more frequent monitoring
required on initiation or adjustment of levothyroxine).
lBREAST FEEDINGAmount too small to affect tests for
neonatal hypothyroidism.
lPRESCRIBING AND DISPENSING INFORMATION
Levothyroxine equivalent to 100 micrograms/m^2 /day can
be used as a guide to the requirements in children.
lPATIENT AND CARER ADVICE
Medicines for Children leaflet: Levothyroxine for
hypothyroidismwww.medicinesforchildren.org.uk/
levothyroxine-for-hypothyroidismlMEDICINAL FORMS
There can be variation in the licensing of different medicines
containing the same drug. Forms available from special-order
manufacturers include: capsule, oral suspension, oral solution
Tablet
▶Levothyroxine sodium (Non-proprietary)
Levothyroxine sodium anhydrous 12.5 microgramLevothyroxine
sodium 12. 5 microgram tablets| 28 tabletP£ 2. 80 – £ 14. 00 DT =
£ 13. 60
Levothyroxine sodium anhydrous 25 microgramLevothyroxine
sodium 25 microgram tablets| 28 tabletP£ 3. 05 DT = £ 1. 87 |
500 tabletP£ 41. 61 – £ 56. 25
Levothyroxine sodium 25 microgram tablets lactose free|
100 tabletPs
Levothyroxine sodium anhydrous 50 microgramLevothyroxine
sodium 50 microgram tablets lactose free| 100 tabletPs
Levothyroxine sodium 50 microgram tablets| 28 tabletP£ 1. 50
DT = £ 0. 97 | 1000 tabletP£ 38. 93 – £ 55. 71
Levothyroxine sodium anhydrous 75 microgramLevothyroxine
sodium 75 microgram tablets| 28 tabletP£ 2. 10 – £ 4. 00 DT = £ 2. 73
Levothyroxine sodium anhydrous 100 microgramLevothyroxine
sodium 100 microgram tablets lactose free| 100 tabletPs
Levothyroxine sodium 100 microgram tablets| 28 tabletP£ 1. 50
DT = £ 0. 96 | 1000 tabletP£ 38. 93 – £ 56. 07
▶Eltroxin(AMCo)
Levothyroxine sodium anhydrous 25 microgramEltroxin
25 microgram tablets| 28 tabletP£ 2. 54 DT = £ 1. 87
Levothyroxine sodium anhydrous 50 microgramEltroxin
50 microgram tablets| 28 tabletP£ 1. 77 DT = £ 0. 97
Levothyroxine sodium anhydrous 100 microgramEltroxin
100 microgram tablets| 28 tabletP£ 1. 78 DT = £ 0. 96
Oral solution
▶Levothyroxine sodium (Non-proprietary)
Levothyroxine sodium anhydrous 5 microgram per
1mlLevothyroxine sodium 25 micrograms/ 5 ml oral solution sugar
free sugar-free| 100 mlP£ 118. 63 DT = £ 94. 94
Levothyroxine sodium anhydrous 10 microgram per
1mlLevothyroxine sodium 50 micrograms/ 5 ml oral solution sugar
free sugar-free| 100 mlP£ 91. 22 DT = £ 89. 66
Levothyroxine sodium anhydrous 20 microgram per
1mlLevothyroxine sodium 100 micrograms/ 5 ml oral solution sugar
free sugar-free| 100 mlP£ 165. 00 DT = £ 164. 88Liothyronine sodium
(L-Tri-iodothyronine sodium)
lINDICATIONS AND DOSE
Hypothyroidism
▶BY MOUTH
▶Child 12–17 years:Initially 10 – 20 micrograms daily;
increased to 60 micrograms daily in 2 – 3 divided dosesHypothyroid coma
▶BY SLOW INTRAVENOUS INJECTION
▶Child 12–17 years: 5 – 20 micrograms every 12 hours,
increased to 5 – 20 micrograms every 4 hours if
required, alternatively initially 50 micrograms for
1 dose, then 25 micrograms every 8 hours, reduced to
25 micrograms twice daily
Hypothyroidism (replacement for oral levothyroxine)
▶BY SLOW INTRAVENOUS INJECTION
▶Child:Convert daily levothyroxine dose to liothyronine
and give in 2 – 3 divided doses, adjusted according to
response
DOSE EQUIVALENCE AND CONVERSION
▶ 20 – 25 micrograms of liothyronine sodium is equivalent
to approximately 100 micrograms of levothyroxine
sodium.
▶Brands without a UK licence may not be bioequivalent
and dose adjustment may be necessary.lCAUTIONSCardiac disorders (monitor ECG; start at low
dose and carefully titrate).diabetes insipidus.diabetes
mellitus (dose of antidiabetic drugs including insulin may
need to be increased).prolonged hypothyroidism (initiate
corticosteroid therapy in adrenal insufficiency).severe
hypothyroidism (initiate corticosteroid therapy in adrenal
insufficiency)
lINTERACTIONS→Appendix 1 : thyroid hormones
lSIDE-EFFECTS
GENERAL SIDE-EFFECTS
▶Rare or very rareAlopecia.angina pectoris (more common
at excessive dosage).arrhythmia (more common at
excessive dosage).diarrhoea (more common at excessive
dosage).heat intolerance.muscle cramps.muscle
weakness.palpitations (more common at excessive
dosage).tachycardia (more common at excessive dosage).
vomiting (more common at excessive dosage)
▶Frequency not knownAgitation.fever.flushing.headache
.hyperhidrosis.insomnia (more common at excessive
dosage).oedema.restlessness (more common at excessive
dosage).skin reactions.tremor (more common at
excessive dosage).weight decreased
SPECIFIC SIDE-EFFECTS
▶Rare or very rare
▶With intravenous useEpiphyses premature fusion.
idiopathic intracranial hypertension.menstruation
irregular
lPREGNANCYDoes not cross the placenta in significant
amounts. Excessive or insufficient maternal thyroid
hormones can be detrimental to fetus.
Dose adjustmentsLiothyronine requirement may increase
during pregnancy.
MonitoringAssess maternal thyroid function before
conception (if possible), at diagnosis of pregnancy, at
antenatal booking, during both the second and third
trimesters, and after delivery (more frequent monitoring
required on initiation or adjustment of liothyronine).
lBREAST FEEDINGAmount too small to affect tests for
neonatal hypothyroidism.
lPRESCRIBING AND DISPENSING INFORMATION
Switching to a different brandPatients switched to a different
brand should be monitored (particularly if pregnant or if
heart disease present) as brands without a UK licence may
not be bioequivalent. Pregnant women or those with heart
disease should undergo an early review of thyroid status,
and other patients should have thyroid function assessed if
experiencing a significant change in symptoms. If
liothyronine is continued long-term, thyroid function tests
should be repeated 1 – 2 months after any change in brand.486 Thyroid disorders BNFC 2018 – 2019
Endocrine system6