Drug reference

Folinic acid

Vitamin · Antidote

Also known as Leucovorin, citrovorum factor, N5 formyl THFA

VitaminAntidoteATC V03AF03

CDSCO approvedATC V03AF03

EXCRETION

—

not curated

INTERACTIONS

3 major

SEVERE in our sources

PREGNANCY

FDA category + note

Top interactionssee all 5 →

CeftriaxoneSevereDatabaseDDInter
FluorouracilSevereDatabaseDDInter
TrimethoprimSevereDatabaseDDInter

Mechanism

Folinic acid is a reduced form of folate (N5-formyl-tetrahydrofolate) that does not require activation by dihydrofolate reductase (DHFR). It bypasses the inhibition of DHFR caused by folate antagonist drugs like methotrexate and pyrimethamine. By supplying essential tetrahydrofolate coenzymes, folinic acid allows for one-carbon transfer reactions necessary for purine and thymidylate synthesis, thereby mitigating the myelosuppressive and other toxic effects of these drugs.

Indications

To minimize bone marrow suppression with pyrimethamine (e.g., in toxoplasmosis treatment)To treat methotrexate toxicityUsed in conjunction with pyrimethamine and sulfadiazine for toxoplasmosis treatmentcounteract bone marrow depression in toxoplasmosis treatmentMethotrexate toxicityCitrovorum factor rescue (in certain malignancies after high-dose methotrexate)To enhance anticancer efficacy of 5-fluorouracil (5-FU)To overcome the toxic effects of methotrexateTo overcome the toxic effects of other DHF reductase inhibitors (e.g., trimethoprim or cotrimoxazole)Prevention of megaloblastic anemia due to pyrimethamine therapy for CNS toxoplasmosis

Dosing

Adult: 10 mg orally each day (when used with pyrimethamine for toxoplasmosis)

Contraindications

Ineffective if given > 3 hours after methotrexate (for rescue)
Not needed for simple folate deficiency

Pregnancy & lactation

Pregnancy

Drug interactions

Ceftriaxone

Severe

Database

Drug interaction classified as: others.

Source: DDInter

Fluorouracil

Severe

Database

Drug interaction classified as: synergy.

Source: DDInter

Trimethoprim

Severe

Database

Source: DDInter

Capecitabine

Moderate

Database

Potentiates 5-FU thymidylate synthase inhibition (intended in regimens) — increases toxicity

Use only in defined regimens; monitor mucositis/diarrhoea

Source: Kimi deep-research + Cla

Methotrexate

Moderate

Database

Folinic acid antagonizes methotrexate toxicity to normal cells, allowing for higher doses of methotrexate in cancer therapy ('Citrovorum factor rescue').

Folinic acid (3.0 mg i.v.) should be administered repeatedly as required to counteract methotrexate toxicity, or 1–3 mg i.v. within ½–1 hour after high-dose methotrexate for rescue. It is ineffective if given more than 3 hours after methotrexate.

Source: DDInter

7 additional low-confidence interactions hidden — those rows lack a documented mechanism or management plan in our sources.