Levothyroxine capsules (Tirosint) are contraindicated for use in anyone unable to swallow a capsule, generally including young children < 6 years of age. Do not cut or crush the capsules.[33700]
Levothyroxine tablets are contraindicated for use in patients with untreated subclinical or overt thyrotoxicosis of any etiology; parenteral levothyroxine and levothyroxine capsules should also not be used in patients with these conditions. Use caution when administering levothyroxine to patients with autonomous thyroid tissue to prevent precipitation of thyrotoxicosis. In addition, administer levothyroxine with caution to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis; this is especially important in patients with these conditions that also are older or have heart disease. For any of these patients, if the serum TSH is already suppressed, levothyroxine should not be administered.[53562]
Administration of oral levothyroxine to patients with uncontrolled adrenal insufficiency can cause adrenal crisis and thus administration is contraindicated. Although not specifically contraindicated, parenteral levothyroxine should also not be used in patients with this condition. Adrenal insufficiency should be corrected with replacement glucocorticoids prior to initiation of treatment. Failure to correct the insufficiency may precipitate an acute adrenal crisis when levothyroxine is initiated. Symptoms of adrenal insufficiency can be unmasked or exacerbated by the administration of thyroid hormones.[53562]
Other causes of hypothyroidism (e.g., morphologic hypogonadism and nephroses) should be ruled out prior to beginning treatment with levothyroxine. Patients with hypothyroidism secondary to hypopituitarism are likely to have suppressed adrenal function as well, which should be corrected prior to initiating thyroid replacement therapy. Symptoms of hypopituitarism can be unmasked or exacerbated by the administration of thyroid hormones.[53562]
Oral levothyroxine is contraindicated in patients with an acute myocardial infarction. All levothyroxine dosage formulations are cardiostimulatory and should be used with great caution in patients with angina pectoris or other preexisting cardiac disease, including uncontrolled hypertension, cardiac arrhythmias, coronary artery disease, or a previous myocardial infarction; do not use levothyroxine therapy in patients with heart disease and nontoxic diffuse goiter or nodular thyroid disease if the serum TSH concentration is suppressed. Many authorities recommend lower initial dosages and slower titration of thyroid hormones in patients with heart disease. If adverse cardiac symptoms develop or worsen, reduce or withhold levothyroxine and cautiously restart at a lower dose. Over-treatment with thyroid hormones may cause cardiac stimulation and lead to increased heart rate, cardiac wall thickening and increased cardiac contractility, which may precipitate angina or cardiac arrhythmias. Concomitant administration of levothyroxine with sympathomimetic agents in patients with coronary artery disease may precipitate coronary insufficiency and associated symptoms. Patients with coronary artery disease who are receiving thyroid hormones may be at a higher risk for developing arrhythmias, particularly during surgery.[53562]
Caution should be used in geriatric patients since they may be more sensitive to the cardiac effects of thyroid replacement. In elderly patients with nontoxic diffuse goiter or nodular thyroid disease, levothyroxine should not be used if the serum TSH concentration is already suppressed. In general, lower initial dosages and slower titration are recommended in elderly patients. Overall, thyroid hormone requirements in the elderly are typically 25% lower than in younger adults. Individualization of dosing is recommended.
Symptoms of diabetes mellitus can be unmasked or exacerbated by the administration of thyroid agents. The use of levothyroxine may require alteration in the dosage of antidiabetic regimens. Blood glucose should be monitored closely during concomitant therapy. In addition, withdrawal of thyroid hormones may cause hypoglycemia in susceptible patients.
Thyroid agents should not be used for obesity treatment or for the purpose of weight loss. Normal doses of levothyroxine are not effective in reducing weight in euthyroid patients. Larger doses may produce serious or even life-threatening toxicity, particularly when given in association with sympathetic amines that are used for their anorectic effects.
Levothyroxine use is only justified for treatment of female or male infertility if such infertility is accompanied by hypothyroidism.
Long-term use of levothyroxine has been associated with decreased bone mineral density, particularly in postmenopausal females on greater than replacement doses or in women receiving suppressive doses. Patients should be given the minimum dose necessary for desired clinical and biochemical response to limit risks for osteoporosis.[53562]
Levothyroxine is classified in FDA pregnancy risk category A.[43942] Thyroid hormones undergo minimal placental transfer and human experience does not indicate adverse fetal effects; do not discontinue needed replacement during pregnancy. Also, hypothyroidism diagnosed during pregnancy should be promptly treated. Measure TSH during each trimester to gauge adequacy of thyroid replacement dosage since during pregnancy thyroid requirements may increase. Immediately after obstetric delivery, dosage should return to the pre-pregnancy dose, monitor a serum TSH 6—8 weeks postpartum to assess for needed adjustments.
Thyroid hormones, like levothyroxine, are generally compatible with breast-feeding; minimal amounts of thyroid hormones are excreted in breast milk. The American Academy of Pediatrics considers the use of levothyroxine to be usually compatible with breast-feeding due to a lack of reported adverse effects in nursing infants.[27500] It should be noted that in general, adequate thyroid replacement doses are needed to maintain normal lactation; levothyroxine is often the drug of choice to treat hypothyroidism during pregnancy and lactation. Comparisons of the levels of TSH and other thyroid function tests between breast-fed and bottle-fed infants have been published.[46858] [46859] [46860] Breast milk does not provide sufficient levothyroxine (T4) or liothyronine (T3) to prevent the effects of congenital hypothyroidism; therefore serum levels of TSH in breast-fed hypothyroid infants are markedly elevated.[46858] [46859] Euthyroid babies who were breast-fed did not have differences in TSH levels when compared to euthyroid babies receiving formula feedings.[46860] [46861]
Use caution when administering the Levoxyl brand of levothyroxine tablets to patients with dysphasia or other conditions that compromise the ability to swallow. Choking, gagging, tablets getting stuck in the throat, and dysphagia have been reported, mainly when the intact tablets were not taken with water. Counsel patients to take the tablet with water.[43943]
[Revised : 2013-03-20 16:06:00]
References
Levothyroxine ยาแคปซูล (Tirosint) ที่ contraindicated สำหรับการใช้ในผู้ที่ไม่สามารถกลืนแคปซูล โดยทั่วไปรวมทั้งเด็ก < 6 ปี ตัด หรือสนใจแคปซูล [33700]เม็ด Levothyroxine เป็น contraindicated สำหรับการใช้ในผู้ป่วย thyrotoxicosis subclinical หรือแจ่มแจ้งไม่ถูกรักษาของวิชาการใด ๆ parenteral levothyroxine และแคปซูล levothyroxine ยังไม่ควรใช้ในผู้ป่วยที่มีเงื่อนไขเหล่านี้ ใช้ความระมัดระวังเมื่อจัดการ levothyroxine เพื่อผู้ป่วยที่มีเนื้อเยื่อไทรอยด์อิสระเพื่อป้องกันฝน thyrotoxicosis นอกจากนี้ levothyroxine ระวังดูแลกับผู้ป่วยกับโรคไทรอยด์ nodular goiter กระจายพิษทั้งเพื่อป้องกันฝน thyrotoxicosis นี้มีความสำคัญอย่างยิ่งในผู้ป่วยที่มีเงื่อนไขเหล่านี้ที่ยังมีอายุ หรือมีโรคหัวใจ ใด ๆ ของผู้ป่วยเหล่านี้ ถ้าซีรั่ม TSH จะถูกระงับแล้ว levothyroxine ควรไม่สามารถจัดการ [53562]บริหาร levothyroxine ปากกับผู้ป่วยที่มีไม่เพียงพอ adrenal แพงกว่าอาจทำให้เกิดวิกฤต adrenal และดังนั้น contraindicated การจัดการ แม้ไม่โดยเฉพาะ contraindicated, parenteral levothyroxine ยังไม่ควรใช้ในผู้ป่วยที่มีสภาพเช่นนี้ ไม่เพียงพอ adrenal ควรได้รับการแก้ไข ด้วย glucocorticoids แทนก่อนเริ่มต้นการรักษา ล้มเหลวในการแก้ไขที่ไม่เพียงพออาจ precipitate วิกฤต adrenal เป็นเฉียบพลันเมื่อเริ่ม levothyroxine อาการของ adrenal ไม่เพียงพอสามารถอำพราง หรือเลวร้าย โดยฮอร์โมนต่อมไทรอยด์ [53562]ควรปกครองออกพร่อง (เช่น morphologic hypogonadism และ nephroses) สาเหตุอื่น ๆ ก่อนที่จะเริ่มต้นรักษา ด้วย levothyroxine ผู้ป่วยพร่องถึง hypopituitarism มัธยมมักจะระงับไว้ adrenal ฟังก์ชันเช่น ซึ่งควรได้รับการแก้ไขก่อนที่จะเริ่มการบำบัดทดแทนไทรอยด์ อาการของ hypopituitarism สามารถอำพราง หรือเลวร้าย โดยฮอร์โมนต่อมไทรอยด์ [53562]Oral levothyroxine is contraindicated in patients with an acute myocardial infarction. All levothyroxine dosage formulations are cardiostimulatory and should be used with great caution in patients with angina pectoris or other preexisting cardiac disease, including uncontrolled hypertension, cardiac arrhythmias, coronary artery disease, or a previous myocardial infarction; do not use levothyroxine therapy in patients with heart disease and nontoxic diffuse goiter or nodular thyroid disease if the serum TSH concentration is suppressed. Many authorities recommend lower initial dosages and slower titration of thyroid hormones in patients with heart disease. If adverse cardiac symptoms develop or worsen, reduce or withhold levothyroxine and cautiously restart at a lower dose. Over-treatment with thyroid hormones may cause cardiac stimulation and lead to increased heart rate, cardiac wall thickening and increased cardiac contractility, which may precipitate angina or cardiac arrhythmias. Concomitant administration of levothyroxine with sympathomimetic agents in patients with coronary artery disease may precipitate coronary insufficiency and associated symptoms. Patients with coronary artery disease who are receiving thyroid hormones may be at a higher risk for developing arrhythmias, particularly during surgery.[53562]Caution should be used in geriatric patients since they may be more sensitive to the cardiac effects of thyroid replacement. In elderly patients with nontoxic diffuse goiter or nodular thyroid disease, levothyroxine should not be used if the serum TSH concentration is already suppressed. In general, lower initial dosages and slower titration are recommended in elderly patients. Overall, thyroid hormone requirements in the elderly are typically 25% lower than in younger adults. Individualization of dosing is recommended.Symptoms of diabetes mellitus can be unmasked or exacerbated by the administration of thyroid agents. The use of levothyroxine may require alteration in the dosage of antidiabetic regimens. Blood glucose should be monitored closely during concomitant therapy. In addition, withdrawal of thyroid hormones may cause hypoglycemia in susceptible patients.Thyroid agents should not be used for obesity treatment or for the purpose of weight loss. Normal doses of levothyroxine are not effective in reducing weight in euthyroid patients. Larger doses may produce serious or even life-threatening toxicity, particularly when given in association with sympathetic amines that are used for their anorectic effects.Levothyroxine use is only justified for treatment of female or male infertility if such infertility is accompanied by hypothyroidism.Long-term use of levothyroxine has been associated with decreased bone mineral density, particularly in postmenopausal females on greater than replacement doses or in women receiving suppressive doses. Patients should be given the minimum dose necessary for desired clinical and biochemical response to limit risks for osteoporosis.[53562]Levothyroxine is classified in FDA pregnancy risk category A.[43942] Thyroid hormones undergo minimal placental transfer and human experience does not indicate adverse fetal effects; do not discontinue needed replacement during pregnancy. Also, hypothyroidism diagnosed during pregnancy should be promptly treated. Measure TSH during each trimester to gauge adequacy of thyroid replacement dosage since during pregnancy thyroid requirements may increase. Immediately after obstetric delivery, dosage should return to the pre-pregnancy dose, monitor a serum TSH 6—8 weeks postpartum to assess for needed adjustments.Thyroid hormones, like levothyroxine, are generally compatible with breast-feeding; minimal amounts of thyroid hormones are excreted in breast milk. The American Academy of Pediatrics considers the use of levothyroxine to be usually compatible with breast-feeding due to a lack of reported adverse effects in nursing infants.[27500] It should be noted that in general, adequate thyroid replacement doses are needed to maintain normal lactation; levothyroxine is often the drug of choice to treat hypothyroidism during pregnancy and lactation. Comparisons of the levels of TSH and other thyroid function tests between breast-fed and bottle-fed infants have been published.[46858] [46859] [46860] Breast milk does not provide sufficient levothyroxine (T4) or liothyronine (T3) to prevent the effects of congenital hypothyroidism; therefore serum levels of TSH in breast-fed hypothyroid infants are markedly elevated.[46858] [46859] Euthyroid babies who were breast-fed did not have differences in TSH levels when compared to euthyroid babies receiving formula feedings.[46860] [46861]
Use caution when administering the Levoxyl brand of levothyroxine tablets to patients with dysphasia or other conditions that compromise the ability to swallow. Choking, gagging, tablets getting stuck in the throat, and dysphagia have been reported, mainly when the intact tablets were not taken with water. Counsel patients to take the tablet with water.[43943]
[Revised : 2013-03-20 16:06:00]
References
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