The antidote of folic acid antagonist
Calcium folinate is an antidote of the folic acid antagonists. At room temperature, it appears as yellowish white to yellow crystalline or amorphous powder, being odorless. It is easily soluble in water, but almost insoluble in ethanol or ether, and easily soluble in sodium hydroxide solution. Calcium folinate is a formylated derivative of folic acid, acting similarly to folic acid, being the activated form of folic acid in the body. After entering into the human body, it is converted to tetrahydrofolic acid under the action of tetrahydrofolate reductase, being effective in fighting against methotrexate-induced toxicity. Calcium folinate has effect of "rescuing" the in vivo toxicity of the excess amount of folic acid antagonists, being conducive to thymidine, DNA, RNA and protein synthesis, being able to stimulate white blood cell growth and maturation. This product can limit the damage degree of methotrexate to normal cells by competing with each other. It is also able to reverse the reaction of methotrexate on bone marrow and gastrointestinal mucosa, but has no effect on the existing methotrexate neurotoxicity. It is mainly for used as the antidote of the folic acid antagonists (such as methotrexate, aminopterin, phenytoin, phenobarbital, pyrimethamine or trimethoprim, etc.). When oral administration of folic acid yields poor efficacy, it is used for the treatment of stomatitis, diarrhea, malnutrition, pregnancy or infancy-caused megaloblastic anemia and leukopenia. But it is not applicable to vitamin B12 deficiency anemia.
Pharmacological effects
Calcium folinate (CF) is a calcium salt of the calcium formyl tetrahydrofolate derivative, being the activated form of folic acid in the body. It is mainly used as the antidotes of the folic acid antagonist. For example, aminopterin, methotrexate, pyrimethamine and trimethoprim and other drugs can competitively inhibit the dihydrofolate reductase, making folic acid be not able to become tetrahydrofolic acid, leading to DNA synthesis disorders. Supplementation of calcium folinate can have detoxification effect and can treat folic acid-deficiency caused megaloblastic anemia, promote the differentiation, maturation and release of bone marrow hematopoietic cells. In recent years, a large number of experimental and clinical studies at home and abroad have fully proved that leucovorin can be used as a kind of highly efficient biochemical regulator, being able to significantly enhance the anti-tumor activity of the fluorouracil (5-FU) class drug. Fluorouracil is a kind of pyrimidine antagonist, being the major drugs for the treatment of gastrointestinal cancer, breast cancer, head and neck cancer, trophoblastic tumor and many other kinds of malignant tumors. Calcium folinate was easy to be absorbed by oral administration with the serum reduced folic acid reaching peak value at (1.72 ± 0.80) hours;
The time for reaching peak value is (0.71 ± 0.09) hours after intramuscular injection. Intramuscular injection of serum folic acid gives a half-life of 3.5 hours with the drugs effect being maintained for 3 to 6 hours. The metabolite product is 5-methyl tetrahydrofolate with 80% to 90% being subject to renal excretion.
Uses
1. Calcium Folinate is mainly used as the antidote of folic acid antagonists (such as methotrexate, pyrimethamine or trimethoprim, etc.);
2. Calcium Folinate can be used for the prevention of severe toxicity after excessive or large doses administration of methotrexate.
3. The megaloblastic anemia caused by folic acid deficiency.
4. In combination with fluorouracil, it is used for the treatment of advanced colon cancer and rectal cancer.
It is used for the rescue of the toxicity reaction caused by excessive amount of aminopterin and methotrexate as well as being used for the treatment of giant red blood cell anemia.
The efficacy of folate can offset the effects of folic acid antagonists. The folic acid antagonists rely on binding to folic acid dehydrogenase (DHFR), thereby preventing folate from converting to folic acid. Medically, after the chemotherapy of methotrexate, the calcium folinate can be used to reduce methotrexate toxicity. Calcium folinate can be used to enhances the cytotoxic effect of 5-fluorouracil in anticancer fields.
Usage and precautions
For the treatment of megaloblastic anemia, administrate orally 15 mg daily; or daily intramuscularly inject 1~5 mg; after 10~15 d, we can reduce the amount to 5 mg/d for oral administration until hemogram becomes normal and the symptoms disappear; if we can’t rule out the possibility of adenosine deficiency, we should combine with adenosine cobalt amine. For the rescue of methotrexate, apply 3 to 4 times per day with oral administration of 5~15 mg per time for 2d; or apply intramuscular injection of 3~6 mg; applying this drug is invalid for the treatment of patients who have administrated methotrexate for over 4 h. For the detoxification of pyrimethamine or trimethoprim, administrate orally 5~15 mg per day. Calcium folinate can be used in combination with fluorouracil at 20~30mg/m2. Administrate orally at half an hour after administration of fluorouracil.
Contraindications
Calcium Folinate is contraindicated in patients who have previously shown hypersensitivity to folinate or any of the excipients.
Calcium Folinate Injection is contraindicated in the treatment of pernicious anaemia or other megaloblastic anaemias where vitamin B12 is deficient. Its use can lead to an apparent response of the haematopoietic system, but neurological damage may occur or progress if already present.Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take calcium folinate tablets.
Side effects
There is occasionally rash, urticaria or asthma. Patients of megaloblastic anemia caused by pernicious anemia or vitamin B12 deficiency should be disabled. It is not suitable to be simultaneously applied together with folic acid antagonists such as methotrexate.
Special warnings and precautions
Apply this drug after the high-dose usage of methotrexate for 24~48h; be cautious when using it for the methotrexate detoxification therapy on patients of acidic urine, ascites, dehydration, gastrointestinal obstruction, pleural effusion or renal dysfunction; for patients in critical conditions, the drug dose should be increased; the creatinine clearance rate should be measured before the treatment. After the application of high-dose methotrexate, we need to measure the plasma or serum methotrexate concentration every 12~24 h. Before or after the treatment of methotrexate, we need to measure the amount of serum creatinine every 24 h. In cases when the value after treatment is over 50% greater than that before treatment, this indicates severe renal toxicity.
Chemical Properties
Light yellow to yellow solid
Originator
Leucovorin calcium,AstraZeneca
Uses
Calcium folinate offsets the effects of folic acid antagonists that act by binding dihydrofolate reductase and blocking the conversion of folic acid to tetrahydrofolate. In medicine, calcium folinate is used after treatment with methotrexate to reduce the toxicity of the methotrexate. Calcium folinate is also used to enhance the cytotoxic effect of 5-fluorouracil in the treatment of cancer.
Uses
antianemic, antidote to folic acid antagonists.
Calcium folinate (folinic acid, calcium leucovorin, tetrahydrofolate) can be used in the management of methotrexate overdose and to reduce the toxicity of high-dose methotrexate chemotherapy.Calcium folinate is a reduced form of folic acid, which bypasses the inhibition of dihydrofolate reductase by methotrexate.Calcium folinate also has a role in combination with fluorouracil in the treatment of bowel cancer, where its use enhances the effect of fluorouracil by inhibition of thymidilate synthase.
Definition
ChEBI: Calcium folinate is a tetrahydrofolic acid.
Manufacturing Process
5,10-Methenyl-5,6,7,8-tetrahydrofolic acid, chloride hydrochloride dihydrate
(20 g) was added in one portion to 100 ml water at 60°C followed by N,Ndiethylethanolamine (14.9 g) which adjusted the pH to 6. The mixture was
maintained at reflux for 5 hours and the pH kept between 5.7 and 6.2 by
addition of N,N-diethylethanolamine. The mixture was cooled, synthetic
magnesium silicate (15 g) added and slurried, and filtered through celite and
diluted with 40 ml SD3A (95% ethanol with 5% methanol). The filtrate was
kept at -5°C for 16 hours, aqueous calcium chloride (4.0 g) was added
dropwise to the cold filtrate, and the precipitate filtered, washed with SD3A
(100 ml) and with ethyl acetate (100 ml) and dried under reduced pressure.
brand name
Wellcovorin (GlaxoSmithKline).
Therapeutic Function
Antidote (folic acid antagonists), Antianemic
General Description
Pharmaceutical secondary standards for application in quality control, provide pharma laboratories and manufacturers with a convenient and cost-effective alternative to the preparation of in-house working standards.
Biochem/physiol Actions
Folinic acid serves as a cofactor and participates in one-carbon-transfer reactions. It helps in improving wound healing in rats. Folinic acid plays a major role in children with autism to enhance verbal communication.
Mechanism of action
The mechanism of action of Calcium folinate against cancer is to stabilise the complex between 5-FU and thymidylate synthase, thereby enhancing the cytotoxicity of 5-FU, a pyrimidine analogue and inhibitor of thymidylate synthase, which blocks DNA production. Thymidylate synthase converts deoxyuridine monophosphate to thymine monophosphate. Administration of 5-FU reduces deoxythymidine monophosphate, preventing DNA synthesis and leading to cell death.
