- Circumstances, associated or not with hypothyroidism, where it is necessary to slow down the TSH.
In younger patients, and in the absence of heart disease, a serum Levothyroxine (T4) level of 70 to 160 nanomols per litre, or a serum thyrotrophin level of less than 5 milli-units per litre should be targeted. A pre-therapy ECG is valuable because ECG changes due to hypothyroidism may be confused with ECG evidence of cardiac ischaemia. If too rapid an increase in metabolism is produced (causing diarrhoea, nervousness, rapid pulse, insomnia, tremors, and sometimes anginal pain where there is latent cardiac ischaemia,) dosage must be reduced, or withheld, for a day or two, and then re-started at a lower dose level.
Adults: Initially, 50 to 100 micrograms daily (two to four tablets daily), preferably taken before breakfast or your first meal of the day. Adjust at three to four week intervals by 50 micrograms until normal metabolism is steadily maintained. The final dose may be up to 100 to 200 micrograms.
Elderly: as for patients aged over 50 years
For patients over 50 years, initially, it is not advisable to exceed 50 micrograms daily. In this condition, the daily dose may be increased by 50 micrograms at intervals of every 3-4 weeks, until stable thyroxine levels are attained. The final daily dose may be up to 50 to 200 micrograms.
Patients over 50 years with cardiac disease:
Where there is cardiac disease, 25 micrograms daily or 50 micrograms on alternate days is more suitable. In this condition, the daily dosage may be increased by 25 microgram increments at intervals of every 4 weeks, until stable thyroxine levels are attained. The final daily dose may be up to 50 to 200 micrograms.
For patients aged over 50 years, with or without cardiac disease, clinical response is probably a more acceptable criteria of dosage rather that serum levels.
The maintenance dose is generally 100 to 150 micrograms per m2 body surface area. The dose for children depends on their age, weight and the condition being treated. Regular monitoring using serum TSH levels, as in adults, is required to make sure he/she gets the right dose. Infants should be given the total daily dose at least half an hour before the first meal of the day.
Congenital hypothyroidism in infants:
For neonates and infants with congenital hypothyroidism, where rapid replacement is important, the initial recommended dosage is 10 to 15 micrograms per kg body weight per day for the first three months. Thereafter, the dose should be adjusted individually according to the clinical findings and thyroid hormone and TSH values.
Acquired hypothyroidism in children:
For children with acquired hypothyroidism, the initial recommended dosage is 12.5-50 micrograms per day. The dose should be increased gradually every two to four weeks according to the clinical findings and thyroid hormone and TSH values until the full replacement dose is reached.
Infants should be given the total daily dose at least half an hour before the first meal of the day.
Juvenile myxoedema in children:
The initial recommended dosage is 25 micrograms daily. In such conditions, the daily dose may be increased by 25 micrograms at intervals of every 2 - 4 weeks, until mild symptoms of hyperthyroidism are seen. The dose will then be reduced slightly.
In children under 5 years of age, the administration of whole tablets is not recommended. It is also not recommended that tablets are crushed and dispersed in water or other liquids, owing to limited solubility which could lead to dosing inaccuracy. In this age group it is preferable to administer an approved oral solution of levothyroxine.
Method of administration
For oral use.
Hair loss may occur during the first few months of treatment. This effect is usually temporary as your body adjusts to this medication. If this effect lasts or gets worse, tell your doctor or pharmacist promptly.
Consult your doctor or pharmacist prior to starting or stopping a new medication.