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PHARMACOLOGICAL ACTIVITIES - TOXICOLOGY - DRUG INTERACTIONS

Folic Acid [Vitamin B ] (C H N O )
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The terms folic acid and folate are often used interchangeably, folic acid, the more stable form,
occurs rarely in foods. The function of folate coenzymes in the body is to mediate the transfer
of one-carbon units (Choi & Mason, 2000). Folate coenzymes act as acceptors and donors
of one-carbon units in a variety of reactions critical to the metabolism of nucleic acids and
amino acids (Bailey & Gregory, 1999). Deficiency of folic acid can cause macrocytic anemia,
megaloblastic anemia, leucopenia, elevated plasma iron concentration, and weight loss (NRC,
1986).

TOXICOLOGY Toxicity for folic acid has not been documented in dogs and cats when administered orally in therapeutic doses.

The Registry of toxic effects of chemical substances (US Department of Health and Human Services, 1979) gives
two LD values for folic acid in mice, intraperitoneal 100 mg/kg of body weight and intravenous 239 mg/kg of
50
body weight (Parchure et al., 1985).

DRUG NSAIDs such as aspirin or ibuprofen may interfere with folate metabolism when taken in
INTERACTIONS very large therapeutic dosages. Phenytoin, has been shown to inhibit the intestinal absorption
of folate, and several studies have associated decreased folate status with long-term use of
the anticonvulsants, phenytoin, phenobarbital, and primidone (Lewis et al., 1995; Apeland
et al., 2001). Taking folic acid at the same time as the cholesterol-lowering agents such as
cholestyramine and colestipol, may decrease the absorption of folic acid (Hendler & Rorvik,
2001). A number of other medications have been shown to have antifolate activity, including
tetracycline, trimethoprim, pyrimethamine, triamterene, and sulfasalazine (UMMC, 2012d).

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