General: If the dose of levothyroxine is increased too rapidly, symptoms such as diarrhoea, nervousness, rapid pulse, insomnia, tremors and sometimes anginal pain where there is latent myocardial ischemia may occur, and the dosage must be reduced or withheld for a day or two, then restarted at a lower level. A pre-therapy ECG is valuable, as changes induced by hypothyroidism may be confused with ECG evidence of ischaemia.
Adults: Initially 50 to 100 micrograms daily, and adjusted at 4 to 6 week intervals by 50 micrograms until attainment of clinical and biochemical euthyroidism. This may require doses of 100 to 200 micrograms daily.
With patients aged over 50 years, it is not advisable to exceed 50 micrograms a day initially. Where there is cardiac disease, 50 micrograms on alternate days is more suitable.