Vancomycin Hydrochloride

Glycopeptide Antibiotic Tricyclic glycopeptide antimicrobial

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV (slow infusion over 60 min) 15 mg/kg q8h Duration: Varies; typically 7-14 days depending on infection
Notes: Dose adjustment required in renal impairment. Therapeutic drug monitoring recommended (trough 10-20 mcg/mL).
Dog Oral 10-20 mg/kg q6-8h Duration: 5-7 days for C. difficile colitis
Notes: Oral route for local GI infections only; not absorbed systemically.
Cat IV (slow infusion over 60 min) 15 mg/kg q8-12h Duration: Varies; typically 7-14 days
Notes: Dose adjustment required in renal impairment. Therapeutic drug monitoring recommended.
Cat Oral 10-20 mg/kg q6-8h Duration: 5-7 days for C. difficile colitis
Notes: Oral route for local GI infections only.
Horse IV (slow infusion over 30-60 min) 6.6-7.5 mg/kg q6-8h Duration: Varies; often 7-14 days
Notes: Dose adjustment in renal impairment. Monitor for nephrotoxicity and ototoxicity.
Cattle IV (slow infusion) 15 mg/kg q8h Duration: Varies; extra-label use only
Notes: Not approved for food animals; withdrawal times must be extended. Use with caution.
Small Ruminants IV (slow infusion) 15 mg/kg q8h Duration: Varies; extra-label use only
Notes: Not approved for food animals; withdrawal times must be extended.
Rabbit IV (slow infusion) 15 mg/kg q8-12h Duration: Varies; extra-label use
Notes: Use with caution; monitor renal function.
Bird/Poultry IV (slow infusion) 15 mg/kg q8-12h Duration: Varies; extra-label use
Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications
  • Treatment of serious infections caused by susceptible gram-positive bacteria, especially methicillin-resistant staphylococci and enterococci, when other antibiotics are ineffective or contraindicated
Dog (Canine)
  • Treatment of serious gram-positive infections, including methicillin-resistant Staphylococcus pseudintermedius (MRSP) and methicillin-resistant Staphylococcus aureus (MRSA) infections
  • Treatment of enterococcal infections (e.g., Enterococcus faecium) resistant to other antibiotics
  • Treatment of bacterial endocarditis, osteomyelitis, pneumonia, and septicemia caused by susceptible gram-positive organisms
  • Oral treatment of Clostridioides difficile-associated diarrhea (off-label)
Cat (Feline)
  • Treatment of serious gram-positive infections, including MRSA and MRSP infections
  • Treatment of enterococcal infections resistant to other antibiotics
  • Treatment of septicemia, endocarditis, and pneumonia caused by susceptible gram-positive organisms
  • Oral treatment of Clostridioides difficile-associated diarrhea (off-label)
Horse (Equine)
  • Treatment of gram-positive infections, including Rhodococcus equi pneumonia (in combination with rifampin or macrolides)
  • Treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections
  • Treatment of septic arthritis, osteomyelitis, and endocarditis caused by susceptible gram-positive organisms
Cattle (Bovine)
  • Oral treatment of Clostridioides difficile-associated diarrhea (off-label)
Rabbit & Small Mammals
  • Treatment of severe gram-positive infections (e.g., Staphylococcus aureus, Clostridium sp.) under extra-label use
  • Oral treatment of Clostridioides difficile-associated diarrhea (off-label)
Exotic & Other Species
  • Treatment of severe gram-positive infections in reptiles, small mammals, and exotic species under extra-label use

Pharmacology & Mechanism of Action

Drug Class: Glycopeptide Antibiotic | Pharmacological Group: Tricyclic glycopeptide antimicrobial

Mechanism of Action: Vancomycin inhibits bacterial cell wall synthesis by binding with high affinity to the D-alanyl-D-alanine terminus of cell wall precursor units (lipid II and its derivatives). This binding prevents the transglycosylation and transpeptidation steps in peptidoglycan synthesis, leading to a defective cell wall and ultimately bacterial cell lysis. It is bactericidal against most gram-positive organisms, but bacteriostatic against enterococci.

Pharmacodynamics: Vancomycin exhibits time-dependent killing and has a post-antibiotic effect (PAE) of 1-2 hours for staphylococci. Its activity is primarily against aerobic and anaerobic gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), and Enterococcus species. It is not active against gram-negative bacteria, mycobacteria, or fungi. Resistance can emerge via alteration of the D-Ala-D-Ala target to D-Ala-D-Lac or D-Ala-D-Ser.

⚡ Pharmacokinetics Summary

Absorption: Vancomycin is poorly absorbed after oral administration, with negligible systemic absorption. It acts locally in the gastrointestinal tract. After parenteral administration (IV), absorption is complete.
Distribution: Vancomycin distributes widely into body fluids and tissues, including pleural, pericardial, ascitic, and synovial fluids. It penetrates poorly into the cerebrospinal fluid (CSF) unless the meninges are inflamed. It crosses the placenta and is distributed into milk. Volume of distribution is approximately 0.4-1 L/kg in dogs and cats.
Metabolism: Vancomycin undergoes minimal metabolism. It is primarily excreted unchanged by the kidneys via glomerular filtration. A small amount may be metabolized to inactive products.
Excretion: Vancomycin is excreted primarily by the kidneys via glomerular filtration, with approximately 80-90% of an IV dose recovered in urine within 24 hours. In patients with renal impairment, excretion is significantly reduced, requiring dose adjustment. Biliary excretion is minimal.
Half-Life: Dogs: 1.5-4 hours; Cats: 2-6 hours; Horses: 1.5-2 hours; Humans: 4-6 hours (with normal renal function). Half-life is prolonged in renal impairment.
Bioavailability: Oral: <5% (systemic); IV: 100%.
Protein Binding: Approximately 30-55% protein bound in dogs and cats; 10-50% in other species.

Available Formulations & Strengths

Powder for Injection (as hydrochloride) 500 mg/vial, 1 g/vial, 5 g/vial, 10 g/vial (IV)
Oral Capsule 125 mg, 250 mg (PO)
Oral Solution (reconstituted) 250 mg/5 mL, 500 mg/5 mL (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to vancomycin or other glycopeptides
  • Severe renal impairment (unless dose adjusted and monitored)
  • Pre-existing hearing loss (relative contraindication due to ototoxicity)
  • Concurrent use with other nephrotoxic or ototoxic drugs (e.g., aminoglycosides, loop diuretics) unless absolutely necessary
Warnings & Clinical Precautions:
  • Use with caution in patients with renal insufficiency; adjust dose and monitor renal function and serum drug concentrations.
  • Infusion-related reactions (red man syndrome) can occur with rapid IV infusion; infuse over at least 60 minutes and consider premedication with antihistamines.
  • Monitor for ototoxicity, especially in patients with renal impairment or those receiving other ototoxic drugs.
  • Prolonged use may result in overgrowth of nonsusceptible organisms, including fungi.
  • Oral vancomycin is not effective for systemic infections; use only for local GI infections.
  • In food animals, extra-label use is prohibited in some countries; check local regulations.
  • Use in pregnant or lactating animals only if clearly needed; safety not established.

Adverse Effects & Reactions

Common:

  • Phlebitis at injection site
  • Red man syndrome (erythema, flushing, pruritus, hypotension) with rapid infusion
  • Nausea, vomiting, diarrhea (especially with oral administration)
  • Fever
  • Eosinophilia

Serious / Severe:

  • Nephrotoxicity (acute kidney injury, increased creatinine)
  • Ototoxicity (hearing loss, tinnitus, vertigo)
  • Severe hypotension
  • Anaphylaxis
  • Stevens-Johnson syndrome (rare)
  • Neutropenia, thrombocytopenia (rare)

Rare:

  • Pseudomembranous colitis (with oral use)
  • Drug rash with eosinophilia and systemic symptoms (DRESS)
  • Linear IgA bullous dermatosis
  • Interstitial nephritis

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Aminoglycosides (e.g., gentamicin, amikacin) Additive nephrotoxicity and ototoxicity; increased risk of renal failure and hearing loss. High
Loop diuretics (e.g., furosemide) Additive ototoxicity and nephrotoxicity. High
Nonsteroidal anti-inflammatory drugs (NSAIDs) Increased risk of nephrotoxicity due to reduced renal perfusion. Moderate
Neuromuscular blocking agents Vancomycin may enhance neuromuscular blockade; monitor for prolonged paralysis. Moderate
Warfarin Vancomycin may potentiate the anticoagulant effect; monitor coagulation parameters. Moderate
Contrast media (IV iodinated contrast) Increased risk of nephrotoxicity when used concurrently. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Nephrotoxicity (elevated BUN, creatinine, oliguria)
  • Ototoxicity (hearing loss, tinnitus, vertigo)
  • Hypotension
  • Red man syndrome (with rapid infusion)
  • Anaphylaxis (rare)

Emergency Treatment Protocol: There is no specific antidote. Treatment is supportive and symptomatic. For severe overdose, consider hemodialysis or hemoperfusion to enhance elimination. Maintain adequate hydration and monitor renal function, hearing, and vital signs. Discontinue the drug and adjust subsequent doses based on renal function.

Food Animal Withdrawal Times

Vancomycin is not approved for use in food animals in many countries. Extra-label use in food animals is prohibited in the US (per AMDUCA) because it is a medically important antimicrobial for humans. In other countries, if used, extended withdrawal times must be established based on pharmacokinetic data; consult a veterinary pharmacologist. No official withdrawal times are available.

Storage, Handling & Regulatory Information

Storage Temperature: Store powder for injection at controlled room temperature 20-25°C (68-77°F); reconstituted solutions are stable for 14 days under refrigeration (2-8°C) or 96 hours at room temperature. Oral capsules and solution should be stored at room temperature, protected from moisture.

Handling & Special Conditions: Protect from freezing. Reconstituted solutions should be inspected for particulate matter and discoloration before use. Discard unused portions.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Vancomycin is not FDA-approved for veterinary use in the US. It is approved for human use. Veterinary use is extra-label.

Extra-Label (Off-Label) Use: In the US, extra-label use of vancomycin in food animals is prohibited by the FDA because it is a critically important antimicrobial for human medicine. In companion animals, extra-label use is permitted under AMDUCA with appropriate veterinary oversight. In the EU, similar restrictions apply. Use in food animals is generally discouraged.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Vancomycin is a potent glycopeptide antibiotic reserved for serious gram-positive infections, particularly those caused by methicillin-resistant staphylococci and enterococci. In veterinary medicine, it is used off-label in companion animals (dogs, cats, horses) when other antibiotics fail. Due to the risk of nephrotoxicity and ototoxicity, therapeutic drug monitoring is strongly recommended, especially in patients with renal impairment or those receiving prolonged therapy. The drug must be infused slowly over at least 60 minutes to avoid infusion-related reactions. Oral vancomycin is used only for local GI infections like C. difficile colitis, as it is not absorbed systemically. Because of its importance in human medicine, judicious use is essential to preserve its efficacy. Always check local regulations regarding extra-label use and withdrawal times in food animals.

References & Literature

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