Vitamin b?
Pharmacology:
pharmacodynamics
Vitamin B6 is converted into pyridoxal phosphate in red blood cells, which is used as a coenzyme for various metabolic functions of protein, carbohydrates and lipids. Vitamin B6 is also involved in the process of converting nicotinic acid into 5- hydroxytryptamine by tryptophan.
pharmacokinetics
Mainly absorbed in the jejunum. Vitamin B6 does not bind to plasma protein, while pyridoxal phosphate completely binds to plasma protein. T 1/2 as long as 15 ~ 20 days. Metabolism in the liver and excretion through the kidney. It can be discharged through hemodialysis.
Indications:
(1) is suitable for the prevention and treatment of vitamin B6 deficiency and isoniazid poisoning; It can also be used for vomiting and seborrheic dermatitis caused by pregnancy, radiation sickness and anticancer drugs.
(2) Total parenteral nutrition and vitamin B6 supplements are used for malnutrition and progressive weight loss caused by insufficient intake.
*(3) The demand for vitamin B6 is increased in the following situations: pregnancy and lactation, hyperthyroidism, scald, long-term chronic infection, fever, and congenital metabolic disorder [cystathioninuria, hyperoxaluria, hypercystinuria, and xanthuric acid urine]. Congestive heart failure, long-term hemodialysis, malabsorption syndrome complicated with hepatobiliary diseases (such as alcoholism complicated with cirrhosis), intestinal diseases (celiac disease, tropical stomatitis enteritis, localized enteritis, persistent diarrhea), after gastrectomy. The intake of vitamin B6 in daily diet is related to people's intake of protein.
* (4) Newborn hereditary vitamin B6 dependence syndrome, which is characterized by irritability and epileptic spasm, should be treated with vitamin B6 within one week after birth to prevent anemia and mental retardation.
* (5) Vitamin B6 has no definite effect on the following diseases, such as acne and other skin diseases, alcoholism, asthma, kidney calculi's disease, psychosis, migraine, premenstrual tension, stimulation of milk secretion, loss of appetite, etc.
Usage and dosage:
1. Common oral doses for adults: ① vitamin B6 dependence syndrome, starting with 30 ~ 600 mg per day, and maintaining the dose of 50mg per day for life; ② vitamin B6 deficiency, 10 ~ 20mg daily for 3 weeks, then 2 ~ 3mg daily for several weeks; ③ Congenital metabolic disorder (cystathioninuria, hyperoxaluria, hypercystinuria, xanthinuria),100 ~ 500mg per day; ④ To prevent vitamin B6 deficiency caused by drugs, take 10 ~ 50mg daily (using penicillamine) or 100 ~ 300mg daily (using cycloserine, ethionine or isoniazid) for 50 ~ 200mg daily for * * 3 weeks, and then 25 ~ 65438 daily. ⑤ Hereditary sideroblastic anemia, 200 ~ 600 mg daily, * * * 1 ~ 2 months, and then 30 ~ 50 mg daily for life; 6 alcoholism, 50 mg per day.
Common doses for children: ① Vitamin B6 dependence syndrome, infant maintenance dose, 2 ~ 10 mg per day, life-long application, and the dosage of 1 year-old children is the same as that of adults; ② Vitamin B6 deficiency, 2.5 ~ 10 mg per day for 3 weeks, and then 2 ~ 5 mg per day for several weeks.
2. Common doses for intramuscular or intravenous injection in adults: ① Vitamin B6 dependence syndrome, starting with 30 ~ 600 mg per day, maintaining 50mg per day, and taking orally for life; ② Drug-induced vitamin B6 deficiency was 50 ~ 200mg daily for * * 3 weeks, and then 25 ~100mg daily as needed; (3) Detoxification: Cycloserine poisoning patients should take more than 300mg per day, and isoniazid poisoning patients should take intravenous injection of vitamin B6 from 65438 0g to 65438 0g per day.
[Preparation and specifications] Vitamin B6 tablets 10mg
Vitamin B6 injection (1) 1 ml: 25mg (2) 1 ml: 50mg (3) 2ml:100mg.
Oral, 10-20mg once, three times a day; Intramuscular injection, intravenous drip or subcutaneous injection, 50- 100mg once,/kloc-0 once a day.
Disable warning:
Long-term and large-scale use by pregnant women can cause neonatal vitamin B6 dependence syndrome. It is characterized by irritability and epileptic spasm.
Instructions for administration:
The recommended daily dietary intake (RDA, 1980) for children aged 4-6 years is 1.3mg, 2.2mg for adults (male and female), 2.6mg for pregnant women and 2.5mg for lactating women.
Taking a large amount of vitamin B6 in pregnant women will lead to vitamin B6 dependence syndrome in newborns. Normal intake by lactating mothers has no adverse effects on babies.
It is not appropriate to use high-dose vitamin B6[ more than 10 times the amount specified in RDA( 1980)] to treat some diseases that have not been proved effective.
Vitamin B6 affects the therapeutic effect of levodopa on Parkinson's disease, but has no effect on carbidopa.
Adverse reactions:
When renal function is normal, vitamin B6 is almost non-toxic. It is reported that if you take 200 mg every day for more than 30 days, vitamin B6 dependence syndrome will occur. Daily application of 2 ~ 6g for several months can cause severe nerve sensory abnormality, and progressive gait instability leads to numbness of feet and inflexibility of hands, which can be relieved after drug withdrawal, but it is still weak.
To treat leukopenia, 50- 100mg and 20ml of 5% glucose solution were injected intravenously once a day. Some cases have allergic reactions. When used in large doses, memory loss and transaminase increase may occur. Long-term and large-scale use can cause serious peripheral neuritis.
Oral administration can cause constipation, lethargy and loss of appetite. Injection can cause a serious headache.
Vitamin B6 alone or in combination with vitamin B 12 will aggravate acne vulgaris or make acne rash erosion.
Interaction:
(1) Chloramphenicol, cycloserine, ethionine, hydrazine hydrochloride, immunosuppressants including adrenocortical hormone, cyclophosphamide, cyclosporine, isoniazid, penicillamine and other drugs can antagonize vitamin B6 or increase the excretion of vitamin B6 through the kidney, which can cause anemia or peripheral neuritis.
(2) The dosage of vitamin B6 should be increased when taking estrogen.
(3) The combination of levodopa and low-dose vitamin B6 (5mg daily) can antagonize the anti-tremor effect of levodopa.
The combination of levodopa and a small amount of vitamin B6 can antagonize the anti-tremor effect of levodopa, but the problem does not exist when decarboxylase inhibitors are added at the same time.