What Is Methocarbamol?

Thiourea antithyroid drugs mainly inhibit thyroxine synthesis. The mechanism of action is to inhibit the oxidation of thyroid peroxidase, prevent the oxidation of iodide in the thyroid and the coupling of tyrosine, thereby hindering the synthesis of thyroxine (T4) and triiodothyronine (T3). This product does not block the release of stored thyroid hormones, so only after the body has eliminated thyroid hormones and the concentration in the circulation has decreased, it will have a significant clinical effect. In addition, propylthiouracil also inhibits T4 deiodination to T3 in peripheral tissues.

Thiourea antithyroid drugs mainly inhibit thyroxine synthesis. The mechanism of action is to inhibit the oxidation of thyroid peroxidase, prevent the oxidation of iodide in the thyroid and the coupling of tyrosine, thereby hindering the synthesis of thyroxine (T4) and triiodothyronine (T3). This product does not block the release of stored thyroid hormones, so only after the body has eliminated thyroid hormones and the concentration in the circulation has decreased, it will have a significant clinical effect. In addition, propylthiouracil also inhibits T4 deiodination to T3 in peripheral tissues.

Chinese name

Methionine

Foreign name

Methylthiouracil

Types of

Thiourea antithyroid drugs

Tablets

50mg, 100mg

Drug classification

Endocrine System Drugs-Drugs for Thyroid Diseases

Methionine

Chinese name: methionine

Chinese synonyms: methylthiouracil; 4-hydroxy-2-mercapto-6-methylpyrimidine; 2,3-dihydro-6-methyl-2-thio-4 (1H) -pyrimidinone; 4- Methyl-2-thiouracil; 4-methylthiouracil; 6-methyl-2-thiouracil; 6-methylthiouracil; methylthiouracil

English name: Methylthiouracil

English synonyms: LABOTEST-BB LT00848091; Aurora KA-4696; METHIOCIL; METHYLTHIOURACIL; 2-THIO-6-METHYLURACIL; 4-OXO-2-MERCAPTO-6-METHYLPYRIMIDINE; 4-HYDROXY-2-MERCAPTO-6-METHYLPYRIMIDINE; 4 -HYDROXY-6-METHYL-2-THIOPYRIMIDINE

CAS: 56-04-2 ^[1]

Chemical structure:

Melting point: ~ 330 ° C (dec.) (Lit.)

Water solubility: INSOLUBLE

Stability: Stability Incompatible with strong oxidizing agents, iodine, metals.

Methylthiouracil chemical properties

White crystals. Decomposes at 326-331 ° C. Soluble in ammonia solution and sodium hydroxide solution, slightly soluble in alcohol and acetone, very slightly soluble in water and ether, insoluble in benzene and chloroform. The saturated aqueous solution is neutral or slightly acidic to litmus. No odor, bitter taste, easy to sublimate.

Methionine

Intermediate of the cardiovascular drug Persantin.

Method for producing methionine

Derived from the reaction of ethyl acetoacetate and thiourea. The thiourea was dissolved in a sodium hydroxide solution, and ethyl acetoacetate was added dropwise to control the temperature below 37 ° C. After 2 hours of reaction, water and activated carbon were added and decolorization was performed at 70-80 ° C for 0.5 h. After filtration, the filtrate was acidified with hydrochloric acid to pH 4-5, cooled to room temperature, filtered, and washed. The filter cake was recrystallized from water to obtain a finished product. Yield: 66%. In production, ethyl acetoacetate and thiourea can also be mixed first, and then sodium oxide solution can be added dropwise; anhydrous sodium carbonate can also be used instead of sodium hydroxide, and the yield is about the same.

Methothiopyrimidine Methothiopyrimidine Related Drug Product Information

1 Specification for Methionine ^[2-3]

1.1 Drug name

Methionine

1.2 English name

Methythiouracil

1.3 Alias of methionine

Methylthiouracil

1.4 Classification

Endocrine System Drugs> Drugs for Thyroid Diseases

1.5 dosage form

1). Molecular formula and molecular weight C ₅ H ₆ N ₂ OS; 142.2.

2). 50mg and 100mg tablets.

1.6 Pharmacological effects of methionine

Propiothiouracil can inhibit thyroid peroxidase, thereby inhibiting the iodination of tyrosine and the condensation of iodized tyrosine, hindering the biosynthesis of thyroid hormones. It does not affect the uptake of iodine and the release and utilization of T4 and T3. It does not directly fight thyroid hormones, and it is necessary to wait for the generated thyroid hormones to be consumed before they can produce curative effects. Generally speaking, symptoms can be improved within 2 to 3 weeks, and basal metabolism returns to normal within 1 to 3 months. It can inhibit deiodinase in peripheral tissues, thereby inhibiting the conversion of T4 to T3, and reducing the T3 content in serum. In addition, the drug still has an immunosuppressive effect, which can slightly inhibit the production of immunoglobulins, reduce the thyroid stimulating immunoglobulin (TSI) content in the blood circulation, and has a certain effect on the therapeutic effect. The basic role of methionine is the same as that of propylthiouracil, but there are more adverse reactions and it is now rarely used.

1.7 Pharmacokinetics of methionine

Oral absorption is rapid, and it starts to appear in the blood in 20-30 minutes. It reaches a peak concentration in 2 hours, bioavailability is 80%, and plasma protein binding rate is about 75%. And through the placenta, it is mainly metabolized in the liver and partially excreted after combining with glucuronic acid, t1 / 2 is 2h.

1.8 Indications for methionine

1). Medical treatment of hyperthyroidism is suitable for patients with mild and inoperable surgery or radioactive iodine.

2). The treatment of thyroid crisis, in addition to eliminating the incentives, taking comprehensive measures, using large doses of iodine to suppress the release of thyroid hormones, while using large doses of thiourea drugs as adjuvant treatment to block the synthesis of thyroid hormones.

3). Preparation before surgery Take methionine before surgery to restore or close to normal thyroid function, which can reduce anesthesia and postoperative complications and prevent thyroid crisis after surgery. At the same time, you must take iodine two weeks before surgery to reduce Congestion to facilitate surgery.

1.9 Contraindications for methionine

Forbidden in patients with nodular goiter complicated with hyperthyroidism and patients with thyroid cancer.

1.10 Notes

Use with caution in pregnant women. Shaded and sealed.

1.11 Adverse effects of methionine

1). There are allergic reactions such as headache, dizziness and itching, drug rash, and gastrointestinal reactions such as loss of appetite, vomiting, diarrhea, etc. In most cases, the drug is not necessary.

2). Serious adverse reactions include leukocytopenia and agranulocytosis, which usually occur within 2 to 3 months after treatment, but they may also occur at any time. Therefore, blood and liver function should be checked regularly during medication, especially with hyperthyroidism The difference is caused by the low total number of white blood cells. If there is sore throat or fever after taking the medicine, it can be recovered by stopping the medicine immediately.

3). It can have adverse effects on the thyroid function of the fetus and lactating children. It should be used with caution in pregnant women and banned in lactating women. Thioureas also increase TSH secretion, which promotes the development of thyroid cancer.

1.12 Methionine

Oral: 0.05-0.1 g / time for adults, 0.15-0.3 g / d; extreme amount, 0.2 g / time, 0.6 g / d.

1). Medical treatment of hyperthyroidism is started at 0.2 0.6g / d, divided into 3 times. After the symptoms are relieved, the maintenance amount is taken, 25 100mg / d, divided into 1-2 times. The course of treatment is 1 to 2 years.

2). Thyroid crisis 0.4-0.8g / d, divided into 3 to 4 times, the course of treatment does not exceed one week, which is one of the comprehensive treatment measures.

3). Preoperative preparation for hyperthyroidism. Take it before surgery to restore thyroid function to normal or close to normal, and then take iodine for two weeks before surgery.

1.13 Interactions of Methionine with Other Drugs

The combined use of thioureas and oral anticoagulants can increase the effect of the latter. Lithium salts, sulfonamides, sulfonylureas, p-aminosalicylic acid, p-aminobenzoic acid, bute, barbiturates, phentolamine, vitamin B12, etc. can all inhibit thyroid function to varying degrees. Care should be taken when using urea. Because iodine can delay the onset time of thioureas, avoid using iodine before use.

1.14 Drug Evaluation

Thioureas are the most commonly used antithyroid drugs, and they can be divided into two groups according to their structure: Thioxopyridines, including methithiopyrimidine and propylthiouracil; Imidazoles, including methimazole and carbimazole Wait. The basic role of methionine is the same as that of propylthiouracil, but there are more adverse reactions and it is now rarely used.