Original title: [Great Family Medicine Box] A door and four dings each show your magic to bring you to understand vitamin B12 drugs
Vitamin B12, which is mainly obtained from food, can be treated with vitamin B12 drugs when the body is deficient in vitamin B12 or suffers from diseases such as pernicious anemia. So, what are the vitamin B12 classes of drugs? What are the indications? What problems should I pay attention to during medication? This article takes you through the use of vitamin B12 drugs.
□ Zhang Shige
In 1926, George Minot, an assistant professor at Harvard University and a hematologist, was inspired by the article by physiologist Wheat to try to make patients with pernicious anemia eat beef liver to relieve symptoms, and after 2 months, the patient's anemia symptoms were significantly reduced. In 1948, the American medical scientist Rex isolated a red crystal from the liver, believing it to be an anti-pernicious anemia internal factor. This red crystal was named cyanocobalamin and later merged into the B vitamin family, sorted as vitamin B12. Vitamin B12, which is mainly obtained from food, can be treated with vitamin B12 drugs when the body is deficient in vitamin B12 or suffers from diseases such as pernicious anemia.
Four members
There are 4 members of the vitamin B12 family, including cyanocobalamin (vitamin B12), methylcobalamin, adenosine cobalamin, and hydrocobalamin (the latter three are the active coenzyme forms of vitamin B12). The structure of these four drugs is different, the difference is that the X positions connected to cobalt in their structures are cyanide, methyl, deoxyadenosine, and hydroxyl groups.
After being absorbed by oral or injection, cyanocobalamin is stored in the liver and converted into methylcobalamin, adenosine cobalamin, and hydroxycobalamin. Methylcobalamin, adenosylcobalamin and hydrocobalamin do not require conversion after oral or injection and can function directly in the human body.
Each has its own symptoms
To sum up, vitamin B12 drugs are mainly used to treat megaloblastic anemia (which can be used in combination with folic acid according to symptoms), vitamin B12 deficiency caused by malnutrition, hepatitis, cirrhosis, etc., to supplement the vitamin B12 deficiency caused by long-term use of metformin in diabetic patients. In addition, because proton pump inhibitors (omeprazole, rabeprazole, pantoprazole, lansoprazole, esomeprazole, etc.) may hinder the body's absorption of vitamin B12 for normal intake, so long-term proton pump inhibitors should also supplement vitamin B12 in an appropriate amount.
Adenosylcobalamin promotes cell growth and reproduction and maintains the integrity of the myelin sheath of nerve cells. Compared with cyanocobalamin, methylcobalamin is more likely to enter nerve cells, promote the synthesis of cell core acids and proteins, promote axon regeneration, and restore the synaptic transmission function and the number of neurotransmitters. Therefore, methylcobalamin and adenosine cobalamin are often used to treat diabetic peripheral neuropathy, facial nerve palsy, glaucoma visual field defects, neuropathy in hemodialysis patients, sciatica, trigeminal neuralgia, neuralgia in lumbar disc herniation, neuritis or nerve damage.
Hydroxycobalamin can be used to treat vitamin B12 deficiency and can also be used to treat cyanide poisoning. Hydroxycobalamin can be affinity with cyanogen ions, therefore, after the cyanogen ions in the body encounter hydroxycobalamin, they can quickly replace the hydroxyl groups in the hydroxycobalamin molecule to form a non-toxic cyanocobalamin, which is excreted through the urine.
Cyanocobalamin, adenosyltalamin, and hydrocobalamin can be injected intramuscularly; methylcobalamin can be injected intramuscularly, intravenously, and orally. Intramuscular cyanocobalamin is 25 to 100 μg once daily, or 50 to 200 μg every other day. The dose of intramuscular injection of adenosylcobalamin is 0.5 to 1.5 mg/time once a day. Hydroxycobalamin is injected once every other day in week 1 with 0.25 to 0.5 mg each time, and once a week at the beginning of weekly injection of 0.25 mg at weekly intervals at week 2, until the red blood cell count returns to normal, and then maintain 0.25 mg every 3 to 4 weeks. For the treatment of neuritis, neuralgia and cyanide poisoning requires increased doses. Methylcobalamin can be given intramuscularly or intravenously 500 micrograms 3 times a week, and in patients with megaloblastic anemia, 500 micrograms once every other day, after 2 months of treatment, the maintenance dose is switched to (i.e., 500 micrograms every 1 to 3 months). Among the 4 classes of drugs, only methylcobalamin can be taken orally at an oral dose of 500 μg each time, 3 times a day; if continuous administration is ineffective for 1 month, it is not necessary to use it again.
Apply it appropriately
When vitamin B12 is treated for megaloblastic anemia, serum potassium levels should be monitored for the first 48 hours to prevent hypokalemia. Some patients often consume too much iron in the body due to the acceleration of hemoglobin synthesis in the later stages of treatment, resulting in iron deficiency. Therefore, in the course of megaloblastic anemia, if the hemoglobin rises to a certain level and then stagnates, iron supplementation should be promptly supplemented.
Patients with gout should monitor indicators such as uric acid during the use of vitamin B12 drugs. Injections of vitamin B12 drugs in patients with heart disease may increase blood volume, lead to pulmonary edema or congestive heart failure, and should be used with caution.
Vitamin B12 deficiency may be accompanied by folic acid deficiency, and folic acid supplementation should be accompanied by folic acid supplementation according to your own situation.
Cyanocobalamin and methylcobalamin can cause induration and pain at the injection site, and repeated injections should be avoided at the same site.
During the medication period, occasional allergic reactions, rashes, headaches, fever, blood pressure drops, breathing difficulties and other adverse reactions should be treated in time.
(Author Affilications:Beijing Jishuitan Hospital) (Zhang Shige)
Editor-in-Charge: Xiao Yun
【Source: China Medical News】
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