folic acid

Therapeutic Classification: antianemics, vitamins

Pharmacologic Classification: water soluble vitamins

Indications ⬆ ⬇

REMS

Prevention and treatment of megaloblastic and macrocytic anemias.
Given during pregnancy to promote normal fetal development.

Action ⬆ ⬇

Required for protein synthesis and red blood cell function. Stimulates the production of red blood cells, white blood cells, and platelets. Necessary for normal fetal development.

Therapeutic effects:

Restoration and maintenance of normal hematopoiesis.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed from the GI tract and IM and SUBQ sites.

Distribution: Half of all stores are in the liver. Enters breast milk. Crosses the placenta.

Protein Binding: Extensive.

Metabolism/Excretion: Converted by the liver to its active metabolite, dihydrofolate reductase. Excess amounts are excreted unchanged by the kidneys.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(↑ in reticulocyte count)

ROUTE	ONSET	PEAK	DURATION
PO, IM, SUBQ, IV	30–60 min	1 hr	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Uncorrected pernicious, aplastic, or normocytic anemias (neurologic damage will progress despite correction of hematologic abnormalities);
Pedi: Preparations containing benzyl alcohol should not be used in newborns.

Use Cautiously in:

Undiagnosed anemias.

Adv. Reactions/Side Effects ⬆ ⬇

Derm: rash

Neuro: confusion, difficulty sleeping, irritability, malaise

Misc: fever

Interactions ⬆ ⬇

Drug-drug:

Pyrimethamine, methotrexate, trimethoprim, and triamterene prevent the activation of folic acid (leucovorin should be used instead to treat overdoses of these drugs).
Absorption of folic acid is ↓ by sulfonamides (including sulfasalazine), antacids, and cholestyramine.
Folic acid requirements are ↑ by estrogens, phenytoin, phenobarbital, primidone, carbamazepine, or corticosteroids.
May ↓ phenytoin levels.

Route/Dosage ⬆ ⬇

Therapeutic Dose (Folic acid deficiency)

Recommended Daily Allowance

PO IM IV SC (Adults and Children >11 yr): 1 mg/day initial dose then 0.5 mg/day maintenance dose.
PO IM IV SC (Children >1 yr): 1 mg/day initial dose then 0.1–0.4 mg/day maintenance dose.
PO IM IV SC (Infants ): 15 mcg/kg/dose daily or 50 mcg/day.
PO (Adults and Children >15 yr): 0.2 mg/day.
PO (Adults ): Females of reproductive potential: 0.4–0.8 mg/day.
PO (Children 11–14 yr): 0.15 mg/day.
PO (Children 7–10 yr): 0.1 mg/day.
PO (Children 4–6 yr): 0.075 mg/day.
PO (Infants 6 mo–3 yr): 0.05 mg/day.

Availability ⬆ ⬇

(Generic available)

Solution for injection: 5 mg/mL
Tablets: 0.4 mg; 0.8 mg; 1 mg; 5 mg; 25 mg
In combination with: other vitamins and minerals as multiple vitaminsRx, OTC.

Assessment ⬆ ⬇

Assess patient for signs of megaloblastic anemia (fatigue, weakness, dyspnea) before and periodically throughout therapy.

Lab Test Considerations:

Monitor plasma folic acid levels, hemoglobin, hematocrit, and reticulocyte count before and periodically during therapy.
- May cause ↓ serum concentrations of other B complex vitamins when given in high continuous doses.

Implementation ⬆ ⬇

Because of infrequency of solitary vitamin deficiencies, combinations are commonly administered (see Appendix [not included in this PDA edition]).
- May be given SUBQ, deep IM, or IV when PO route is not feasible.
PO: Antacids should be given at least 2 hr after folic acid; folic acid should be given 2 hr before or 4–6 hr after cholestyramine. A 50-mcg/mL oral solution may be extemporaneously prepared by pharmacy for use in neonates and infants.
IV: Solution ranges from yellow to orange-yellow in color.

IV Administration:

Diluent: Dilute with dextrose or 0.9%NaCl.Concentration: 0.1 mg/mL.
May be added to hyperalimentation solution.

Patient/Family Teaching ⬆ ⬇

Encourage patient to comply with diet recommendations of health care professional. Explain that the best source of vitamins is a well-balanced diet with foods from the 4 basic food groups. A diet low in vitamin B and folate will be used to diagnose folic acid deficiency without concealing pernicious anemia.
Folic acid in early pregnancy is necessary to prevent neural tube defects.
Foods high in folic acid include vegetables, fruits, and organ meats; heat destroys folic acid in foods.
Patients self-medicating with vitamin supplements should be cautioned not to exceed RDA. The effectiveness of megadoses for treatment of various medical conditions is unproven and may cause side effects.
Explain that folic acid may make urine more intensely yellow.
Instruct patient to notify health care professional if rash occurs, which may indicate hypersensitivity.
Emphasize the importance of follow-up exams to evaluate progress.

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Pronunciation ⬇

Classifications ⬆ ⬇