FOE-lik A -sid

Therapeutic Classification: antianemics, vitamins

Pharmacologic Classification: water soluble vitamins

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

• 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.

• Restoration and maintenance of normal hematopoiesis.

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.

(↑ in reticulocyte count)

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.

Derm: rash.

Neuro: confusion, difficulty sleeping, irritability, malaise.
Misc: fever.

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.

Therapeutic Dose (Folic acid deficiency)

• 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.

Recommended Daily Allowance

• 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.

(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 vitamins^{Rx, OTC}.

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

• 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.

• 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:

• Dilute with dextrose or 0.9%NaCl.0.1 mg/mL.
• 5 mg/minRate:
• Continuous Infusion: 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
  • 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
  • morphine
  • nafcillin
  • nalbuphine
  • norepinephrine
  • pentamidine
  • phenytoin
  • prochlorperazine
  • promethazine
  • protamine
  • pyridoxine
  • tacrolimus
  • thiamine
  • tobramycin
  • trimethoprim/sulfamethoxazole
  • verapamil
.

• 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.

• Reticulocytosis 2–5 days after beginning therapy.
  • Resolution of symptoms of megaloblastic anemia.
  • Prevention of neural tube defects.