Folic Acid

Vitamin Water-soluble vitamin (B9)

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 5-20 mg/day (total daily dose, can be divided) q24h or divided q12h Duration: Until clinical improvement or as long as deficiency persists
Notes: For deficiency, typical dose is 5-10 mg/day. For pregnancy, 0.5-1 mg/day may be sufficient. Adjust based on response.
Cat PO 2.5-10 mg/day q24h or divided q12h Duration: Until clinical improvement
Notes: Cats may require higher doses due to lower DHFR activity. Monitor for response.
Horse PO 50-100 mg/day q24h Duration: Variable, often 2-4 weeks
Notes: For anemia, doses up to 200 mg/day have been used. Oral supplementation may be less effective due to microbial degradation; consider parenteral if needed.
Cattle PO or IM Calves: 10-20 mg/day PO; Adult cattle: 50-100 mg/day PO or 10-20 mg IM q24h Duration: Variable, often 1-2 weeks
Notes: In ruminants, oral supplementation may be degraded by rumen microbes; parenteral administration may be more effective.
Small Ruminants (sheep, goats) PO or IM 5-20 mg/day PO or 5-10 mg IM q24h Duration: Variable
Notes: Use parenteral if oral absorption is questionable.
Rabbit PO 1-5 mg/kg q24h q24h Duration: Until clinical improvement
Notes: Use with caution; rabbits typically synthesize folate via cecal fermentation. Only use if deficiency is confirmed.
Birds (poultry) PO or IM 0.5-2 mg/kg q24h or in feed at 0.5-1 mg/kg feed q24h or in feed Duration: Variable
Notes: For prevention, supplement feed with 0.5-1 mg/kg. For treatment, higher doses may be needed.
Exotic (reptiles, small mammals) PO 1-5 mg/kg q24h q24h Duration: Until clinical improvement
Notes: Dose based on limited evidence; adjust based on response.

Clinical Indications & Species Uses

General Indications
  • Treatment of folate deficiency
  • Supportive therapy for macrocytic anemia
  • Supplementation during pregnancy, lactation, or periods of rapid growth
  • Adjunct in treatment of methotrexate toxicity (in species where used)
Dog (Canine)
  • Treatment of folate deficiency (e.g., due to malabsorption, chronic gastrointestinal disease, or drug-induced deficiency)
  • Supportive therapy for macrocytic anemia
  • Supplementation during pregnancy and lactation
  • Adjunct in treatment of methotrexate toxicity (though rarely used in dogs)
  • Support for growth in puppies
Cat (Feline)
  • Treatment of folate deficiency (e.g., due to small intestinal disease, exocrine pancreatic insufficiency)
  • Supportive therapy for anemia
  • Supplementation during pregnancy and lactation
  • Adjunct in treatment of methotrexate toxicity (rare)
Horse (Equine)
  • Supportive therapy for anemia (e.g., chronic blood loss, poor nutrition)
  • Supplementation in performance horses (though evidence is limited)
  • Treatment of folate deficiency due to malabsorption or increased demand (e.g., pregnancy, lactation)
Cattle (Bovine)
  • Prevention and treatment of folate deficiency in calves (e.g., due to inadequate intake or malabsorption)
  • Supportive therapy in anemia (e.g., due to parasites or chronic disease)
  • Supplementation in high-producing dairy cows to support milk production and fertility (limited evidence)
Small Ruminants (Sheep / Goat)
  • Treatment of folate deficiency (rare, but may occur with malnutrition or malabsorption)
  • Supportive therapy in anemia
Avian & Poultry
  • Prevention and treatment of folate deficiency in poultry (e.g., poor growth, poor feathering, anemia)
  • Supplementation in breeding birds to improve hatchability
Exotic & Other Species
  • Reptiles: May be used in cases of deficiency due to poor diet or malabsorption.
  • Small mammals (e.g., ferrets, guinea pigs): Supportive therapy for anemia or gastrointestinal disease.

Pharmacology & Mechanism of Action

Drug Class: Vitamin | Pharmacological Group: Water-soluble vitamin (B9)

Mechanism of Action: Folic acid is a synthetic form of folate, a B vitamin essential for DNA synthesis, repair, and methylation. In the body, folic acid is reduced to tetrahydrofolate (THF) via dihydrofolate reductase (DHFR). THF serves as a coenzyme in the transfer of one-carbon units in the synthesis of purines, thymidylate, and amino acids (e.g., methionine). This is critical for cell division, especially in rapidly dividing tissues such as bone marrow, gastrointestinal epithelium, and fetal development. In veterinary medicine, folic acid supplementation supports erythropoiesis and prevents megaloblastic anemia, particularly in cases of folate deficiency or increased demand.

Pharmacodynamics: Folic acid acts as a precursor to active folate coenzymes. It promotes normal hematopoiesis, supports growth, and maintains gastrointestinal mucosal integrity. In dogs and cats, folate deficiency can lead to macrocytic anemia, leukopenia, and poor growth. Supplementation restores folate levels, improving red blood cell production and overall cellular function. In horses, folic acid is involved in red blood cell production and is sometimes used to support athletic performance, though evidence is limited. In poultry, it is essential for feathering, growth, and egg production.

⚑ Pharmacokinetics Summary

Absorption: Folic acid is rapidly absorbed from the proximal small intestine via active transport and passive diffusion at high doses. In monogastric animals (dogs, cats, pigs), absorption is efficient. In ruminants, dietary folate is synthesized by ruminal microbes, so oral supplementation may be less critical; however, synthetic folic acid can still be absorbed. Bioavailability is high for oral formulations, but may be reduced in malabsorptive conditions.
Distribution: Folate is widely distributed throughout the body, with highest concentrations in the liver, where it is stored as polyglutamates. It crosses the placenta and is secreted into milk. In dogs, folate is distributed into cerebrospinal fluid and other tissues.
Metabolism: Folic acid is metabolized in the liver to 5-methyl-THF, the primary circulating form. It undergoes enterohepatic circulation. In some species, folic acid is converted to active forms via DHFR; this enzyme is present in most mammals but may be less active in certain species (e.g., cats have lower DHFR activity, making them more dependent on dietary folate).
Excretion: Folate is excreted primarily in urine as metabolites, with some biliary excretion. Renal reabsorption is efficient, but high doses exceed the renal threshold, leading to increased urinary excretion. In dogs, the half-life is short, requiring daily supplementation.
Half-Life: Dogs: ~1-2 hours (plasma); Cats: ~1-2 hours; Horses: ~2-3 hours; Cattle: ~2-4 hours (ruminal synthesis complicates).
Bioavailability: Oral bioavailability is high (near 100% in monogastric animals when given on an empty stomach). In ruminants, oral bioavailability may be lower due to microbial degradation, but parenteral administration ensures complete bioavailability.
Protein Binding: Folate is only weakly bound to plasma proteins (approximately 50-60% bound, mainly to albumin).

Available Formulations & Strengths

Oral Tablet 1 mg, 5 mg, 10 mg, 20 mg (PO)
Oral Solution 5 mg/mL (PO)
Injectable Solution 5 mg/mL, 10 mg/mL (IV, IM, SC)
Powder for Oral Use Various (e.g., 1% w/w) (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to folic acid or any component of the formulation
  • Patients with undiagnosed anemia (should be evaluated for vitamin B12 deficiency first, as folic acid can mask B12 deficiency)
  • Patients with malignant diseases (unless specifically indicated, as folate may stimulate tumor growth)
  • In animals with known folate-dependent tumors (e.g., some lymphomas) - use with caution
Warnings & Clinical Precautions:
  • Use with caution in animals with renal impairment, as high doses may accumulate.
  • Folic acid can mask vitamin B12 deficiency; always evaluate B12 status before starting supplementation.
  • In cats, due to lower DHFR activity, folic acid may not be as effective as dietary folate; consider using folinic acid (leucovorin) if needed.
  • In ruminants, oral supplementation may be degraded by rumen microbes; consider parenteral administration.
  • Pregnancy: Folic acid is generally safe, but high doses should be avoided unless deficiency is confirmed.
  • Do not use as a sole treatment for anemia without determining the underlying cause.
  • In poultry, ensure proper mixing in feed to avoid toxicity (though rare).

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (rare at normal doses)
  • Unpleasant taste (oral formulations)

Serious / Severe:

  • Masking of vitamin B12 deficiency, leading to neurological damage if B12 deficiency is untreated
  • Allergic reactions (rare)
  • Seizures (reported in humans with high doses, rare in animals)

Rare:

  • Hypersensitivity reactions (urticaria, pruritus)
  • Hyperkalemia (with high doses in humans, not well-documented in animals)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Methotrexate Methotrexate inhibits DHFR, reducing conversion of folic acid to active form. Folic acid may reduce methotrexate efficacy; folinic acid (leucovorin) is preferred for rescue. High
Sulfonamides (e.g., sulfadiazine, sulfamethoxazole) Sulfonamides inhibit bacterial folate synthesis; concurrent use may increase risk of folate deficiency in the host, especially with prolonged therapy. Moderate
Trimethoprim Trimethoprim inhibits DHFR, potentially increasing folate requirements. Supplementation may be needed during long-term therapy. Moderate
Phenytoin Folic acid may decrease phenytoin levels, reducing its anticonvulsant efficacy. Moderate
Barbiturates (e.g., phenobarbital) May increase folate metabolism, leading to deficiency; supplementation may be needed. Mild
Chloramphenicol May interfere with folate utilization; monitor for anemia. Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Folic acid is water-soluble and generally non-toxic; overdose is rare.
  • High doses may cause gastrointestinal upset (vomiting, diarrhea).
  • In humans, very high doses have been associated with seizures, but this is not well-documented in animals.

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Discontinue folic acid and provide fluids. In cases of severe overdose, monitor electrolytes and neurological status. No specific antidote exists.

Food Animal Withdrawal Times

πŸ₯© Meat: 0 daysπŸ₯› Milk: 0 daysπŸ₯š Eggs: 0 days

Folic acid is a vitamin and generally has no withdrawal period. However, for food animals, follow label instructions and consult with a veterinarian. In the US, no withdrawal time is required for folic acid when used according to label.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (20-25Β°C, 68-77Β°F). Protect from moisture.

Light Sensitivity: Light-sensitive β€” protect from direct exposure.

Handling & Special Conditions: Keep in a tightly closed container. Protect from light. Do not freeze oral solutions. Injectable solutions should be stored as per manufacturer's instructions.

Dispensing Status: Over-The-Counter (OTC)

Approval Status: Folic acid is not FDA-approved for veterinary use, but it is a common supplement used in veterinary practice. It is generally recognized as safe (GRAS) for use in animal feeds.

Extra-Label (Off-Label) Use: Folic acid is a vitamin and is generally available over-the-counter. However, extra-label use in food animals must comply with AMDUCA regulations. In the US, folic acid is not approved for use in food animals, but extra-label use is permitted under veterinary supervision with appropriate withdrawal times.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Folic acid is a water-soluble vitamin essential for cellular division and growth. In veterinary practice, it is primarily used to treat folate deficiency, which can occur due to malabsorptive disorders (e.g., inflammatory bowel disease, exocrine pancreatic insufficiency), chronic gastrointestinal disease, or drug interactions (e.g., methotrexate, sulfonamides). It is also used as a supportive therapy for anemia and during pregnancy/lactation. In dogs and cats, folate deficiency is often associated with small intestinal disease, and supplementation can improve clinical signs. In horses, folic acid is sometimes used for anemia, but evidence is limited. In ruminants, ruminal synthesis usually meets requirements, but supplementation may be beneficial in cases of increased demand or deficiency. Folic acid is generally safe, but it is important to rule out vitamin B12 deficiency before starting supplementation, as folic acid can mask B12 deficiency and lead to neurological damage. Doses should be adjusted based on species and clinical response. For food animals, withdrawal times are not required, but extra-label use must comply with regulations. Overall, folic acid is a valuable adjunctive therapy in veterinary medicine, but it should not be used as a sole treatment for anemia without a thorough diagnostic workup.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)