Thyroxil

Control of hypothyroidism. Congenital hypothyroidism in infants. Acquired hypothyroidism in childn. Juvenile myxedema.

Adult Initially 50-100 mcg daily before breakfast or 1st meal of the day. Adjust at 3-4 wk intervals by 50 mcg until normal metabolism is steadily maintained. Final daily dose: 100-200 mcg. Elderly >50 yr Not advisable to exceed 50 mcg daily. Daily dose may be increased by 50 mcg every 3-4 wk intervals, until stable thyroxine levels are attained. Final daily dose: 50-200 mcg. Patient >50 yr w/ cardiac disease 25 mcg or 50 mcg on alternate days. May increase daily dose by 25 mcg at 4-wk intervals, until stable thyroxine levels are attained. Final daily dose: 50-200 mcg. Childn Maintenance dose: 100-150 mcg/m² BSA. Infant Give total daily dose at least ½ an hr before the 1st meal of the day. Acquired hypothyroidism Initially 12.5-50 mcg daily, increased gradually every 2-4 wk. Juvenile myxoedema Initially 25 mcg daily. May increase by 25 mcg at 2-4 wk intervals until mild symptoms of hypothyroidism are seen. Infant & neonate Congenital hypothyroidism Initially 10-15 mcg/kg for the 1st 3 mth.

Should be taken on an empty stomach.

Hypersensitivity. Thyrotoxicosis, adrenal gland disorder or adrenal insufficiency.

Not to be used for the treatment of obesity or wt loss. Treatment in patients w/ panhypopituitarism or other causes predisposing to adrenal insufficiency may cause reactions including dizziness, weakness, malaise, wt loss, hypotension & adrenal crisis; initiate corticosteroid therapy prior to levothyroxine Na. Too high initial dose or too rapid dose increase may cause or aggravate symptoms of angina, arrhythmias, MI, cardiac failure or sudden raise in BP in elderly & in patients w/ cardiac symptoms, DM or diabetes insipidus. Increased thyroid hormone-sensitivity in patients w/ myxedema. Decreased thyroxine absorption in patients w/ malabsorption syndromes. Long-term therapy in women has been associated w/ increased bone resorption, especially in post-menopausal women receiving greater than replacement doses or suppressive doses of levothyroxine. Pregnancy & lactation.

Hypersensitivity reactions eg, skin rash & pruritus; increased appetite, abnormal wt loss; hyperthyroidism; abdominal cramps, nausea, vomiting, diarrhea; headache, tremors, seizure; anginal pain, cardiac arrhythmias, palpitations, tachycardia, increased BP, heart failure, MI; dyspnea; sweating, alopecia; flushing; cramps in skeletal muscle, muscular weakness, premature closure of epiphyses (in childn w/ compromised adult height); craniosynostosis (in infants); anxiety, emotional lability, nervousness, excitability, insomnia, restlessness; menstrual irregularity, impaired fertility; fatigue, heat intolerance, fever.

Increased effects of anticoagulants. May increase phenytoin levels. Enhanced metabolism of thyroid hormones w/ anticonvulsants eg, carbamazepine & phenytoin. Increased metabolism & excretion w/ enzyme inducers eg, rifampicin & barbiturates resulting in increased Na dose requirements. Enhanced effects of sympathomimetic agents. Accelerated response to TCAs. Decreased absorption w/ cholestyramine, Ca-, Al-, Mg-, Fe supplements, Al hydroxide, polystyrene sulfonates, sucralfate, lanthanum, bile acid sequestrants (eg, colestipol), anion/cation exchange resins (eg, kayexalate, sevelamer), Ca carbonate & ferrous sulphate, & PPIs. Decreased intestinal absorption w/ soy-containing compd & high fibre diets. Increased serum conc of thyroxine-binding globulin & increase Na dosage requirements w/ OCs, estrogen, tamoxifen, clofibrate, methadone & 5-fluorouracil. HMG-CoA reductase inhibitors (statins) may increase thyroid hormone requirements. Tyrosine kinase inhibitors (eg, imatinib & sunitinib) was associated w/ increased levothyroxine Na dosage requirements in hypothyroid patients. Medicines that partially inhibit peripheral transformation of T4 to T3 (eg, propranolol, amiodarone, lithium, iodide, oral contrast agents, propylthiouracil, glucocorticoids) lower T3 level & therapeutic effect. Sertraline can reduce serum levels of thyroxine. Levothyroxine can increase the need for insulin or oral antidiabetics in DM patients. Dosage adjustment may be necessary if co-administered w/ cardiac glycosides. Some drugs, including androgens & anabolic steroids, may decrease serum conc of thyroxine-binding globulin. False low plasma conc have been observed w/ concurrent anti-inflammatory treatment eg, phenylbutazone or ASA. Initial transient increase in serum free T4 w/ ASA.

Thyroid Hormones

H03AA01 - levothyroxine sodium ; Belongs to the class of thyroid hormones.

Rx