Folic acid is contraindicated for use in patients with folic acid hypersensitivity.
Folic acid should be used with extreme caution in patients with undiagnosed anemia. Folic acid corrects the hematologic manifestations of pernicious anemia, while the neurologic complications progress, potentially causing irreversible central nervous system effects. Doses greater than 0.4 mg/day should be avoided until the diagnosis of pernicious anemia is ruled out.
Many formulations of folic acid injection contain benzyl alcohol as a preservative. Benzyl alcohol may cause allergic reactions. Folic acid injections should be used cautiously in those patients with benzyl alcohol hypersensitivity. Injectable folic acid preparations containing benzyl alcohol should be avoided in neonates because benzyl alcohol has been associated with ‘gasping syndrome,’ a potentially fatal condition characterized by metabolic acidosis and CNS, respiratory, circulatory, and renal dysfunction. Additionally, the injection products may contain aluminum which may reach toxic concentrations with prolonged administration in patients with impaired renal function or in premature neonates with immature kidneys. Premature neonates may also be at particular risk because they may require large amounts of calcium and phosphate solutions, which also contain aluminum.
Appropriate maternal folic acid intake is essential to the fetus during pregnancy, and no problems with maternal supplementation to achieve adequate intake goals are known. There is significant evidence that fetal neural tube defects can be prevented if folic acid therapy is initiated before pregnancy and continued during pregnancy. Based on evidence from clinical studies, the USPHS, AAP, and ACOG recommend a folic acid intake of 0.4 mg/day PO from food and/or supplements in females during the child-bearing years, and 0.6 mg PO daily throughout pregnancy. Additionally, data indicate that women with previous neural tube defect (NTD) affected pregnancies should increase their folic acid intake to 4 mg/day PO during the period of greatest risk (1 month before and the 3 months after conception). An optimum dosage has not been established; the lowest effective dose for preventing recurrent NTDs is unknown.
Appropriate maternal folic acid intake is important during lactation, and no problems have been identified with supplementation to achieve adequate intake goals during breastfeeding. The American Academy of Pediatrics (AAP) considers folic acid supplementation compatible with breastfeeding.
The folic acid injection products may contain aluminum which may reach toxic concentrations with prolonged administration in patients with renal failure, renal disease, renal impairment, or in premature neonates with immature kidneys.