Author: Gcplive
Source: Center for Drug Evaluation< /p>In recent years, the prevalence of thyroid diseases has been on the rise, and more and more patients are taking levothyroxine, usually for life. There are many factors that affect the efficacy and adverse reactions of levothyroxine. About levothyroxine tablets, you need the following nine points! I. Identifying the manufacturerThe commonly used levothyroxine sodium tablets in China include Euthyrox, Ratis, and Jiaheng. 
Drug Instructions:Uthorax: The absorption of this product can be more than 80%. Latinus: The absorption of oral levothyroxine in the gastrointestinal tract is 40% to 80%. Balance: The average absorption is 50% after oral administration. Therefore, patients must identify the manufacturer when purchasing medicines. If the manufacturer changes, the pharmacist should also promptly notify the clinician. Otherwise, some patients may experience “product substitution problems,” including hypothyroidism or hyperthyroidism. II. Dosage1. Maximum dose Normal people produce 80-100 μg of thyroxine per day, and the absorption of levothyroxine in the gastrointestinal tract is 40%-80%. Except after thyroid cancer resection, the maximum dose of levothyroxine is 200 μg. 
2.Starting doseLevothyroxine can cause cardiac arrhythmias , angina pectoris, elevated blood pressure, etc., the starting dose should be determined according to the patient’s cardiac function, age, etc. 
Third, levothyroxine is also used in patients with hyperthyroidism? 
Levothyroxine is only used for “adjuvant therapy against hyperthyroidism”. Purpose of use:Some patients with hyperthyroidism, the use of antithyroid drugs The dose is difficult to adjust, a little more can cause hypothyroidism, and a little less can cause hyperthyroidism to worsen. Levothyroxine is mainly used for the treatment of “drug-induced hypothyroidism”. For patients with exophthalmos or goiter, a small amount of levothyroxine can also be given as appropriate to inhibit the secretion of thyrotropin (TSH) and relieve the symptoms of exophthalmos and goiter. 4. The best time for taking the medicineRecommended in the instructions: Levothyroxine sodium tablets should be taken 30 minutes before breakfast, on an empty stomach Take the daily dose in one sitting with an appropriate liquid (eg 1/2 glass of water). Tips:At least 30 minutes away from breakfast, best to wake up in the morning Take it immediately after you arrive (best absorbed 60 minutes before breakfast). Why is it not recommended to take it before bed? One is that taking it in the morning is more in line with the circadian rhythm of thyroid hormones, and the other is that taking it before going to bed may affect the patient’s sleep. 5. What should I do if I miss a dose? The half-life of levothyroxine sodium tablets is 7 days. If one day is missed, the blood concentration of levothyroxine sodium will not be greatly affected. ButYes, it is currently recommended to take a missed dose on the day of discovery, or to take a double dose on the following day. 6. How to adjust the dose? The half-life of levothyroxine sodium tablets is 7 days on average, and theoretically, it takes 5 weeks to achieve steady-state blood concentration. Therefore, the clinical diagnosis and treatment guidelines recommend: Determination of serum thyrotropin (TSH) and free thyroxine (FT4) every 4 to 6 weeks< /span>, and adjust the dose according to TSH and FT4 levels until the therapeutic target is achieved. After the treatment reaches the target, the above indicators should be reviewed at least once every 6 to 12 months. Reminder:On the day of the test, the test should be done without taking the medicine. Because after taking the drug, the drug will have a peak absorption, which will have a certain impact on TSH and FT4. 7. Foods that significantly affect drug absorptionThere are many foods that affect the absorption of levothyroxine sodium, including milk, soy products, and high-fiber foods , coffee, grapefruit juice, etc. Therefore, patients should probably take it 30 minutes before breakfast. Reminder:Soy products can reduce the absorption of levothyroxine. Therefore, dose adjustment of levothyroxine may be necessary when starting or stopping nutritional supplementation with soy products. VIII. Drug interactions and treatment measures1. Drugs affecting levothyroxine
2. Effects of levothyroxine on other drugs
Reminder:Some diseases can also affect the absorption of levothyroxine, especially digestive system diseases , such as Helicobacter pylori-infected gastritis, atrophic gastritis, celiac disease, etc. IX. Adverse reactionsLevothyroxine overdose can cause tachycardia, palpitations, arrhythmia, angina pectoris, increased blood pressure, headache, muscle Weakness and cramps, intolerance to heat, sweating, flushing, excitement, insomnia, restlessness, weight loss, menstrual disorders, diarrhea and vomiting. If the above situation occurs, please seek medical attention in time!
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