Showing papers on "Levothyroxine Sodium published in 1997"

Bioequivalence of Generic and Brand-name Levothyroxine Products in the Treatment of Hypothyroidism

Abstract: Objective. —To compare relative bioavailability of Synthroid, Levoxine (Levoxine has been renamed Levoxyl), and 2 generic levothyroxine sodium preparations. Design. —Single-blind (primary investigators blinded), randomized, 4-way crossover trial. Setting. —Ambulatory care. Patients. —Twenty-Two women with hypothyroidism who were clinically and chemically euthyroid and were receiving levothyroxine sodium, 0.1 or 0.15 mg. Interventions. —All patients received each of the 4 levothyroxine products for 6-week periods in the same dosage as their prestudy regimen with no washout period. The order of the drug sequences was randomly determined before study initiation. Main Outcome Measures. —Area under the curve, time to peak serum concentrations, and peak serum concentrations of thyroxine, triiodothyronine, and free thyroxine index for all 4 products. Results. —All data analyses were completed prior to unblinding of the product codes. No significant differences between the 4 products were found in area under the curve or peak serum concentrations of total thyroxine, total triiodothyronine, or free thyroxine index. Although Synthroid produced a more rapid rise in total serum triiodothyronine concentration and a higher total peak serum triiodothyronine concentration than the other products, these differences were not statistically significant ( P =.08). The Food and Drug Administration criterion for relative bioequivalence within 90% confidence intervals (0.8-1.25) was demonstrated ( P Conclusions. —The 4 generic and brand-name levothyroxine preparations studied are different but are bioequivalent by current Food and Drug Administration criteria and are interchangeable in the majority of patients receiving thyroxine replacement therapy. Further investigation is required to determine whether our results are equally applicable to all existing levothyroxine preparations.

Ferrous Sulfate-Induced Increase in Requirement for Thyroxine in a Patient With Primary Hypothyroidism

Abstract: Recent studies have shown that under experimental conditions ferrous sulfate may reduce the gastrointestinal absorption of orally administered levothyroxine sodium in patients with primary hypothyroidism. We describe a patient who became hypothyroid while taking ferrous sulfate. The hypothyroid status was corrected by increasing the dose of levothyroxine. Subsequently, when ferrous sulfate was discontinued, the patient became hyperthyroid while taking the higher dose of thyroid hormone preparation. Since both hypothyroidism and iron deficiency anemia may coexist, additional thyroid function testing is recommended in patients treated concurrently with ferrous sulfate and L-thyroxine.

Heart hypertrophy induced by levothyroxine aggravates ischemic lesions and reperfusion arrhythmias in rats.

Abstract: AIM: To develop a cardiac hypertrophic model in rats. METHODS: Rats were i.p. levothyroxine 0.5 mg.kg-1.d-1 x 10 d. The action potentials of right papillary muscles were recorded by standard glass-microelectrode technique. The left coronary artery was ligated followed by reperfusion and the apparent infarcted zone (AIZ) was determined by tetracycline fluoresence, and the superoxide dismutase (SOD) activity and malondialdehyde (MDA) product in myocardium were also measured. RESULTS: In the rats treated by levothyroxine, the heart was hypertrophic and the action potential duration (APD) and effective refractory period (ERP) were prolonged, the APD20, APD50, APD90, and ERP were prolonged by 80%, 79%, 74%, and 68%, respectively. No changes in resting potential (RP), action potential amplitude (APA), and Vmax were produced. The incidence of heart arrest (8/8) and the risk of death (67 +/- 0) induced by ischemia-reperfusion in rats with hypertrophic heart was higher than those in normal rats (4/10 and 44 +/- 19, respectively). The AIZ was expanded markedly in hypertrophic heart, and attenuated by lidocaine and propranolol. CONCLUSION: Levothyroxine-induced heart hypertrophy is a suitable model for severe ischemia and arrhythmias in rats.

Increase in Plasma Thyrotropin Levels in Hypothyroid Patients during Treatment due to a Defect in the Commercial Preparation

Abstract: Around mid-1995, the Molecular Endocrinology Laboratory of the Regional Hospital (Malaga, Spain) began detecting an increase in TSH levels in the serum of patients under study to control the treatment of hypothyroidism with levothyroxine. Over a period of 5 months, of a total of 467 hypothyroid patients treated with Levothroid, 53% had TSH levels higher than 6 mU/mL. The reliability of the biochemical results was verified by duplicating 56 randomly chosen samples from all those with high TSH levels and by an external control performed in four different laboratories. The amount of levothyroxine in the tablets was analyzed by RIA, high performance liquid chromatography, and their iodine contents. The lowest levels of levothyroxine found in the 50-mg Levothroid tablets were those determined by RIA, with a mean value of 32.3 mg, resulting in a 35.3% loss of activity. The mean value of levothyroxine found in these same tablets by high performance liquid chromatography was 39.3 mg, amounting to a 21.3% loss in activity. The iodine showed no significant loss in these tablets, with a mean experimental value of 48 mg. The commercial laboratory withdrew lot J from the market, the one in which these deficiencies were found. (J Clin Endocrinol Metab 82: 3192‐3195, 1997)

Hormonal suppressive therapy of thyroid nodules

Abstract: We studied 426 patients in order to analyse the effectiveness of levothyroxine in treating patients with cold thyroid nodules. Nodule volume ranged initially from 0.1 to 10 mL and was measured over a 3 to 18 month-period of treatment using ultrasonography. Nodule variation was studied in each case according to levels of TSH and others factors (age, sex, familial thyroid history, initial volume of nodule and of thyroid gland, date of diagnosis, ultrasonic findings, duration of treatment). Nodule volume increased in 32.6% and significantly decreased (> 50%) in 35.8%. In 2.8% the nodule disappeared. No correlation was found between variation of thyroid nodules and TSH levels under treatment. Similarly no relationship was found between volume variation and other criteria. These results suggest that TSH suppressing doses of levothyroxine are of no advantage in reducing the volume of cold thyroid nodules compared to lower doses.

Manifestation of Primary Hyperthyroidism after Pituitary Adenomectomy : A Case Report

Abstract: We report a 47-year-old Japanese man who presented with visual disturbance due to a pituitary tumor with suprasellar extension. The patient had mild secondary hypothyroidism preoperatively, and was started on administration of levothyroxine sodium immediately before transsphenoidal surgery. After the operation, levothyroxine sodium was continued for several months. Pathological examination of the surgical specimen, together with endocrinological investigation revealed that the suprasellar tumor was a FSH-producing pituitary adenoma. Since 3 months after the operation, he has developed muscle weakness and finger tremor. He was found to be thyrotoxicosis, and levothyroxine sodium was discontinued. Seven weeks after levothyroxine sodium was discontinued, thyrotoxicosis continued, with a positive thyrotropin binding inhibitory immunoglobulin (TBII) and a high diffuse 123I-uptake by the thyroid. He was started on thiamazole 30 mg/day. Although his thyroid dysfunction improved within 2 months, hyperthyroidism worsened repeatedly on attempts to discontinue thiamazole, and he required continuous treatment at 2.5 mg/day. Patients with occult autoimmune thyroiditis rarely progress to thyrotoxicosis after operations on other endocrine organs such as the adrenal or parathyroid gland. In patients with pituitary adenoma, thyroid function and thyroid-associated autoantibodies should be investigated pre- and post-operatively.

More on screening for mild thyroid failure.

Abstract: To the Editor —In trying to replicate the results of the article on screening for mild thyroid failure by Mr Danese and colleagues, 1 I found a mathematical error in one of the assumptions of the cost-effectiveness model Consequently, the analysis overestimates the effect of levothyroxine sodium on symptom relief and underestimates the costs of screening Danese and colleagues assumed there was "symptomatic improvement in 28% of patients with mild thyroid failure" This estimate comes from 2 randomized trials of treatment for mild thyroid failure 2,3 In one of these trials, 2 treatment with levothyroxine sodium relieved symptoms in 8 of 17 patients vs 3 of 16 patients in the placebo group The difference of 8 of 17 (047) less 3 of 16 (019), or 028, is the net benefit or effect size of treatment Its reciprocal, approximately 4, is the number needed to treat to benefit 1 patient However,