folic acid

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.

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).
Sulfonamides (including sulfasalazine), antacids, and cholestyramine may ↓ absorption.
Folic acid requirements are ↑ by estrogens, phenytoin, phenobarbital, primidone, carbamazepine, or corticosteroids.
May ↓ levels and effectiveness of phenytoin.

Route/Dosage ⬆ ⬇

Therapeutic Dose (Folic acid deficiency)

PO IM IV SC (Adults and Children >11 yr): 1 mg/day initially, then 0.5 mg/day maintenance dose.
PO IM IV SC (Children >1 yr): 1 mg/day initially, then 0.1–0.4 mg/day maintenance dose.
PO IM IV SC (Infants ): 15 mcg/kg/dose daily or 50 mcg/day.

Recommended Daily Allowance

PO (Adults and Children >15 yr): 0.2 mg/day.
PO (Adults ): Women 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 for signs of megaloblastic anemia (fatigue, weakness, dyspnea) before and periodically throughout therapy.

Lab Test Considerations:

Monitor folic acid, hemoglobin, hematocrit, and reticulocyte count before and periodically during therapy.
- May ↓ 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 >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:

IV Push: Diluent: Dilute with dextrose or 0.9% NaCl.Concentration: 0.1 mg/mL.
Continuous Infusion: Diluent: May be added to hyperalimentation solution.
Y-Site Compatibility:
- aminophylline
- ascorbic acid
- atracurium
- atropine
- azathioprine
- aztreonam
- benztropine
- bumetanide
- calcium gluconate
- cefazolin
- cefotaxime
- cefotetan
- cefoxitin
- ceftazidime
- ceftriaxone
- cefuroxime
- chloramphenicol
- cimetidine
- clindamycin
- cyanocobalamin
- cyclosporine
- dexamethasone
- digoxin
- diphenhydramine
- dopamine
- enalaprilat
- ephedrine
- epinephrine
- epoetin alfa
- erythromycin
- esmolol
- famotidine
- fentanyl
- fluconazole
- furosemide
- ganciclovir
- glycopyrrolate
- heparin
- hydrocortisone
- imipenem/cilastatin
- indomethacin
- insulin regular
- ketorolac
- labetalol
- letermovir
- lidocaine
- magnesium sulfate
- mannitol
- meperidine
- methylprednisolone
- metoclopramide
- metoprolol
- midazolam
- multivitamins
- naloxone
- nitroglycerin
- nitroprusside
- ondansetron
- oxacillin
- penicillin G
- pentobarbital
- phenobarbital
- phentolamine
- phenylephrine
- phytonadione
- potassium chloride
- procainamide
- propranolol
- sodium bicarbonate
- succinylcholine
- sufentanil
- theophylline
- vancomycin
- vasopressin
Y-Site Incompatibility:
- amikacin
- calcium chloride
- chlorpromazine
- dantrolene
- diazepam
- diazoxide
- dobutamine
- doxycycline
- gentamicin
- haloperidol
- hydralazine
- minocycline
- morphine
- nafcillin
- nalbuphine
- norepinephrine
- pentamidine
- phenytoin
- prochlorperazine
- promethazine
- protamine
- pyridoxine
- tacrolimus
- thiamine
- tobramycin
- trimethoprim/sulfamethoxazole
- verapamil

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy.
Advise patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care provider before taking other medications.
Encourage patient to comply with diet recommendations of health care provider. Explain that the best source of vitamins is a well-balanced diet with foods from the four basic food groups. A diet low in vitamin B and folate will be used to diagnose folic acid deficiency without concealing pernicious anemia.
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 provider if rash occurs, which may indicate hypersensitivity.
Rep: Folic acid in early pregnancy is necessary to prevent neural tube defects. Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding.

section name header

Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇