The active ingredient of Euthyroxine/Retex is levothyroxine (L-T4), which has a clear content and good efficacy, and is mainly used as a supplement and replacement therapy for hypothyroidism caused by various reasons. However, because clinicians and patients do not know enough about it and do not know how to take it, they often mistakenly believe that the drug is “ineffective”, resulting in poor control of the disease. In fact, there are many reasons that can affect the absorption of Eugenol/Retex, resulting in a decrease in the concentration of the drug. The recommended time to take the medication is early in the morning on an empty stomach, with breakfast only 30 minutes after taking the medication, and some studies have reported that eating 60 minutes after taking the medication is best. This is because taking the drug with food may affect the absorption of the drug. For slightly larger doses, the drug can also be taken in two doses, early in the morning on an empty stomach before bedtime (3 hours after dinner). Some people may ask: Why is it not routinely recommended to take the medication before bedtime? Because taking the medication early in the morning is more in line with the circadian rhythmical changes of thyroid hormones. Generally speaking, it peaks 5-6 hours after taking the medication. If you take it at night and it peaks around 3:00 am, your heart will be so excited that it will make your heart skip a beat, so do you want to sleep happily? But in daily life, drug compliance is also a problem that needs to be considered. Many young people nowadays wake up late but need to fix breakfast before going to work, in this case, taking medication before going to bed may be the best choice. Extirpine and colestipol can form insoluble complexes with L-T4 and prevent absorption. Therefore, Eugenol/Retex should be taken 4-5h before taking cholestyramine and colestipol. Drugs containing aluminum, iron and calcium: such as gastric mucosa protector aluminum thioglycollate, antacid aluminum hydroxide, calcium tablets, etc. can complex with L-T4 in the intestine and prevent its absorption. Therefore, Eugenol/Retex should be taken at least 2h before taking the above drugs. Drugs affecting the PH of gastric juice: H2 receptor blockers and proton pump inhibitors affect the PH by inhibiting gastric acid secretion and hinder its absorption. Therefore, Eugenol/Retex should be taken at least 4h before taking the above mentioned drugs. Diseases that affect the absorption of Eugenol such as celiac disease, cirrhosis, gastric acid deficiency and other absorption disorder syndromes. In addition, because of the lactose content in Eugenol, some patients who are lactose intolerant may be intolerant to Eugenol. Since L-T4 is mainly metabolized in the liver, any drugs with liver enzyme-inducing effects, such as barbiturates, phenytoin sodium, carbamazepine, rifampin, etc., will accelerate the metabolism of L-T4 and increase the hepatic clearance rate, resulting in a shorter duration of action in the body and a decrease in blood concentration. Therefore, when patients take these drugs at the same time, they need to increase the dosage of Eugenol/Retex. Supplementation of thyroid hormones and re-establishment of hypothalamic-pituitary-thyroid axis balance usually takes 4-6 weeks. Therefore, at the beginning of treatment, the relevant hormone indicators are measured every 4-6 weeks, and then the dosage of Eugenol is adjusted according to the test results until the treatment goal is reached. After the treatment target is reached, the relevant hormone indexes need to be rechecked every 6-12 months. If the treatment does not reach the target, the reason should be carefully searched. For patients with papillary thyroid cancer, TSH suppression therapy is a very important tool. However, it is clinically found that some patients have taken theoretically enough Eugenol/Retex, but the TSH level is still not well suppressed. What could be the reason for this? If we think that the amount of Eugenol is sufficient, but TSH is still not suppressed, ask the following points. 1.The source of Eugenol: Some patients buy their Eugenol from pharmacies, but we cannot rule out the possibility that pharmacies may have fake drugs. 2. If you can be sure that the eugenol is from a regular hospital, you need to further confirm whether the time of taking the medicine is correct; whether you have drunk milk, soy milk, etc. immediately after taking the medicine, and whether you have taken calcium tablets, etc., because these can affect the absorption of eugenol. 3., Any gastrointestinal diseases, whether taking proton pump inhibitors, etc.; any manifestation of lactose intolerance, such as diarrhea after drinking milk. 4. If all of the above are ruled out, then consider other factors: such as thyroid hormone resistance syndrome, relatively rare with deiodinase abnormalities; even rarer etiology is pituitary gland simply responding poorly to T3. After ruling out factors affecting the absorption of eugenol, you can try to increase the dose of the drug or replace part of the L-T4 with thyroid tablets, which contain T3, and then recheck the thyroid function. If TSH is suppressed, it suggests that there is a real possibility that deiodinase abnormalities are the cause in this group of patients. However, note that deiodinase abnormalities only occur in patients after total thyroidectomy and are therefore uncommon. Finally, store as described in the medication instructions: refrigerate below 25°C.