Thyroxil Dosage/Direction for Use

In younger patients, and in the absence of heart disease, a serum Levothyroxine (T4) level of 70 to 160 nanomoles per liter, or a serum thyrotrophin level of less than 5 milli-units per liter should be targeted. A pre-therapy ECG is valuable because ECG changes due to hypothyroidism may be confused with ECG evidence of cardiac ischemia. If too rapid an increase in metabolism is produced (causing diarrhea, nervousness, rapid pulse, insomnia, tremors, and sometimes anginal pain where there is latent cardiac ischemia) dosage must be reduced, or withheld, for a day or two, and then re-started at a lower dose level.
Adults: Initially 50-100 micrograms daily (2 to 4 tablets daily), preferably taken before breakfast or first meal of the day. Adjust at three to four week intervals by 50 micrograms until normal metabolism is steadily maintained. The final daily 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 dose may be increased by 25 micrograms 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 criterion of dosage rather that serum levels.
Pediatric population: The maintenance dose is generally 100 to 150 micrograms per square meter 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 BW per day for the first 3 months. Thereafter, the dose should be adjusted individually according to the clinical findings, 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 2 to 4 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 myxedema 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 is 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: Oral.