Niacinamide

Vitamin B3 (Nicotinamide) Water-soluble vitamin

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 250-500 mg per dog (for dermatologic conditions); for small dogs (<10 kg) 125-250 mg q8h (every 8 hours) Duration: Typically 2-4 months; may be used long-term for chronic conditions
Notes: Often used in combination with doxycycline (5-10 mg/kg q12h) or other tetracyclines for immune-mediated dermatoses. Monitor for gastrointestinal upset.
Cat PO 125-250 mg per cat q8h Duration: Variable; based on clinical response
Notes: Limited evidence; use with caution. May be used off-label for inflammatory skin conditions.
Horse PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.
Cattle PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.
Small Ruminants PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.
Rabbit PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.
Bird/Poultry PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.
Exotic/Other PO Not established Not established Duration: Not established
Notes: No standard dosing; not recommended without veterinary guidance.

Clinical Indications & Species Uses

General Indications
  • Nutritional supplement for prevention and treatment of niacin deficiency (pellagra)
  • Adjunct in the management of inflammatory and immune-mediated dermatologic conditions
Dog (Canine)
  • Adjunctive therapy for autoimmune skin diseases (e.g., pemphigus complex, discoid lupus erythematosus)
  • Treatment of inflammatory skin conditions (e.g., sterile pyogranuloma syndrome)
  • Supportive therapy for certain dermatoses (e.g., granulomatous sebaceous adenitis)
  • May be used in combination with tetracycline antibiotics (e.g., doxycycline) for immune-mediated dermatoses
Cat (Feline)
  • May be used off-label for inflammatory skin conditions

Pharmacology & Mechanism of Action

Drug Class: Vitamin B3 (Nicotinamide) | Pharmacological Group: Water-soluble vitamin

Mechanism of Action: Niacinamide is the amide form of niacin (vitamin B3). It serves as a precursor for the synthesis of nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), which are essential coenzymes in numerous redox reactions involved in cellular metabolism, including glycolysis, the citric acid cycle, and oxidative phosphorylation. Niacinamide also acts as an inhibitor of poly(ADP-ribose) polymerase (PARP) enzymes, which are involved in DNA repair and apoptosis, and it modulates cellular calcium signaling. In veterinary dermatology, niacinamide is used for its anti-inflammatory and immunomodulatory properties, particularly in the treatment of autoimmune skin diseases such as pemphigus and discoid lupus erythematosus. It is believed to inhibit the release of inflammatory cytokines and histamine, and to stabilize mast cells.

Pharmacodynamics: Niacinamide exerts anti-inflammatory effects by inhibiting the production of pro-inflammatory cytokines (e.g., TNF-alpha, IL-1, IL-6) and by suppressing the activation of nuclear factor kappa B (NF-κB). It also reduces the release of histamine from mast cells and inhibits eosinophil chemotaxis. In the context of autoimmune dermatoses, niacinamide may modulate the immune response by affecting T-cell function and antibody production. Additionally, niacinamide has antioxidant properties, scavenging free radicals and reducing oxidative stress. It does not cause vasodilation or flushing, unlike niacin, because it does not bind to the niacin receptor (GPR109A).

⚡ Pharmacokinetics Summary

Absorption: Niacinamide is rapidly and completely absorbed from the gastrointestinal tract after oral administration. Absorption occurs primarily in the small intestine via passive diffusion and a sodium-dependent carrier-mediated process. Bioavailability is high, with near-complete absorption.
Distribution: Niacinamide is widely distributed throughout the body, including into tissues and cerebrospinal fluid. It crosses the placenta and is distributed into milk. It is taken up by cells and converted to NAD+ and NADP+.
Metabolism: Niacinamide is metabolized in the liver, primarily by methylation to N-methylnicotinamide, which is then oxidized to N-methyl-2-pyridone-5-carboxamide and N-methyl-4-pyridone-5-carboxamide. It can also be deaminated to nicotinic acid.
Excretion: Niacinamide and its metabolites are excreted primarily in the urine. Renal excretion is dose-dependent, with higher doses leading to increased excretion of unmetabolized niacinamide.
Half-Life: The plasma half-life in dogs is approximately 1-2 hours; in other species, it is short, typically 1-3 hours.
Bioavailability: Oral bioavailability is high, approaching 100% in most species.
Protein Binding: Niacinamide has minimal protein binding (<10%).

Available Formulations & Strengths

Oral Tablet 50 mg, 100 mg, 250 mg, 500 mg (PO)
Oral Capsule 100 mg, 250 mg, 500 mg (PO)
Oral Powder Various bulk powders (PO)
Injectable Solution (not commonly used in veterinary medicine) 100 mg/mL (human formulation) (IV/IM (not recommended in animals))

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to niacinamide or any component of the formulation
  • Severe hepatic impairment (use with caution)
  • Active peptic ulcer disease (may exacerbate)
  • Patients with a history of gout (may increase uric acid levels)
Warnings & Clinical Precautions:
  • Use with caution in patients with liver disease, diabetes mellitus, or gallbladder disease.
  • May cause gastrointestinal upset; administer with food to reduce irritation.
  • High doses may cause hepatotoxicity; monitor liver enzymes during prolonged therapy.
  • Use in pregnant or lactating animals only if clearly needed; safety not fully established.
  • In food animals, withdrawal times must be observed if used off-label.
  • Do not confuse with niacin (nicotinic acid); niacin causes flushing and is not suitable for dermatologic use.

Adverse Effects & Reactions

Common:

  • Gastrointestinal upset (vomiting, diarrhea, decreased appetite)
  • Lethargy
  • Pruritus (rarely)

Serious / Severe:

  • Hepatotoxicity (with high doses or prolonged use)
  • Hyperglycemia (in diabetic patients)
  • Hyperuricemia (may precipitate gout)

Rare:

  • Allergic reactions (rash, urticaria)
  • Coagulation abnormalities (with very high doses)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Tetracyclines (e.g., doxycycline) Synergistic anti-inflammatory effect; commonly used in combination for dermatologic conditions. No adverse interaction. Mild
Antidiabetic agents (insulin, oral hypoglycemics) Niacinamide may affect blood glucose levels; monitor glucose and adjust antidiabetic therapy as needed. Moderate
Anticoagulants (warfarin) High doses of niacinamide may enhance anticoagulant effect; monitor coagulation parameters. Moderate
Uricosuric agents (probenecid, sulfinpyrazone) Niacinamide may reduce the uricosuric effect; monitor uric acid levels. Mild
Hepatotoxic drugs (e.g., azathioprine, ketoconazole) Additive hepatotoxicity; use with caution and monitor liver function. High

Overdose & Toxicity Management

Signs of Toxicity:

  • Gastrointestinal distress (vomiting, diarrhea)
  • Flushing (less common than with niacin)
  • Hepatotoxicity (with massive doses)
  • Hyperglycemia
  • Lactic acidosis (in severe cases)

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce vomiting if ingestion is recent and the animal is conscious. Administer activated charcoal to reduce absorption. Provide intravenous fluids to maintain hydration and promote excretion. Monitor liver enzymes, blood glucose, and electrolytes. In severe cases, consider hemodialysis (though rarely needed).

Food Animal Withdrawal Times

🥩 Meat: 0 days🥛 Milk: 0 days🥚 Eggs: 0 days

Niacinamide is a water-soluble vitamin and is generally considered to have zero withdrawal times. However, if used in food animals, consult the label or veterinary supervision, as extra-label use may require extended withdrawal periods.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (20-25°C or 68-77°F).

Handling & Special Conditions: Keep container tightly closed and protected from moisture. Avoid excessive heat.

Dispensing Status: Over-The-Counter (OTC)

Approval Status: Niacinamide is not FDA-approved for veterinary use; it is used as a nutritional supplement and is generally recognized as safe (GRAS) for use in animal feed. For therapeutic purposes, it is used off-label.

Extra-Label (Off-Label) Use: Niacinamide is a non-prescription vitamin supplement. However, extra-label use in animals is permitted under the Animal Medicinal Drug Use Clarification Act (AMDUCA) when used by or on the order of a licensed veterinarian within a valid veterinarian-client-patient relationship. For food animals, extra-label use may require extended withdrawal times.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Niacinamide is a valuable adjunctive therapy in veterinary dermatology, particularly for immune-mediated skin diseases in dogs. It is often used in combination with tetracycline antibiotics (e.g., doxycycline) to achieve a synergistic anti-inflammatory effect. The typical protocol involves administering niacinamide at 250-500 mg per dog every 8 hours, along with doxycycline at 5-10 mg/kg every 12 hours. Clinical response may take several weeks to months. Niacinamide is generally well-tolerated, but gastrointestinal upset can occur; administering with food may help. Liver function should be monitored during prolonged therapy. It is important to distinguish niacinamide from niacin (nicotinic acid), as niacin causes vasodilation and flushing and is not used for dermatologic conditions. Niacinamide is not recommended for use in food animals due to lack of established dosing and withdrawal information, though it is considered safe as a supplement. Always consult a veterinarian for appropriate dosing and monitoring.

References & Literature

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