Procaine with Epinephrine
Procaine hydrochloride with epinephrine bitartrate
Also known as: Willcain · Procaine adrenaline · Novocain with epinephrine
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Dosing by species
Dosing data for this drug is not yet available in the VetSheet formulary. Every other section below is complete. Consult the current product label before prescribing.
Overview
Procaine is a short-acting ester-type local anesthetic. Epinephrine (adrenaline) is added as a vasoconstrictor to prolong the duration of action and reduce the rate of systemic absorption, thereby decreasing the risk of systemic toxicity.
Clinical Pearl: Procaine is rapidly hydrolyzed by plasma pseudocholinesterases, making it relatively safe but very short-acting without the addition of epinephrine. It is primarily used for local infiltration and nerve blocks.
Mechanism of action
Procaine causes a reversible blockade of the voltage-gated sodium channels → prevents the influx of sodium → inhibits the propagation of action potentials along the nerve fiber. Sensory nerve fibers are blocked before motor nerve fibers, allowing a selective sensory blockade at low doses.
Epinephrine stimulates alpha-1 adrenergic receptors → local vasoconstriction → delays systemic absorption of procaine, increasing its local duration of action.
Safety & warnings
Contraindications
- Intravenous administration
- Use in areas supplied by end-arteries (e.g., tail, ears, digits) due to risk of ischemic necrosis
- Known hypersensitivity to ester-type local anesthetics or PABA
- Epidural use (depending on specific formulation preservatives)
Adverse effects
- Local tissue irritation
- Ischemia or tissue necrosis (due to epinephrine)
- CNS excitation followed by depression (at toxic doses)
- Cardiovascular depression, hypotension, or arrhythmias (at toxic doses)
- Allergic reactions (ester anesthetics are metabolized to PABA, a known allergen)
Precautions
WARNING: Do not use epinephrine-containing solutions in extremities or areas with collateral-poor circulation (e.g., tail, ears, digits) due to the risk of severe ischemia and tissue sloughing.
Always aspirate the syringe before injecting to ensure the needle is not in a blood vessel, as accidental intravenous injection can cause severe cardiovascular and CNS toxicity.
Drug interactions
Procaine is metabolized to PABA, which competitively antagonizes the antibacterial effect of sulfonamides.
May antagonize the vasoconstrictive effects of epinephrine.
Sensitizes the myocardium to catecholamines; increased risk of arrhythmias with epinephrine.
Monitoring
- Heart rate and rhythm
- Blood pressure
- Signs of CNS toxicity (tremors, seizures)
- Tissue perfusion at the injection site
Pharmacokinetics
Half-life
Absorption
Systemic absorption is significantly delayed by the vasoconstrictive action of epinephrine.
Distribution
Distributes locally at the injection site; systemic distribution is minimal unless accidentally injected IV or given in large volumes.
Metabolism
Procaine is rapidly hydrolyzed by plasma pseudocholinesterases to para-aminobenzoic acid (PABA) and diethylaminoethanol. Epinephrine is metabolized by COMT and MAO in the liver and tissues.
Elimination
Metabolites are primarily excreted in the urine.
Overdose
Overdose or accidental IV injection can lead to systemic toxicity.
- CNS signs: Restlessness, tremors, seizures, followed by severe CNS depression.
- Cardiovascular signs: Arrhythmias, hypotension, and cardiovascular collapse.
- Treatment: Supportive care, oxygen therapy, control seizures with diazepam or midazolam, and manage arrhythmias. Intravenous lipid emulsion (ILE) therapy may be considered for severe local anesthetic systemic toxicity (LAST).
Available products
Formulations
- Solution for injection
Veterinary
- Willcain Solution for injection
Regulatory status
Approved in various member states under different trade names.
Willcain is classified as POM-VPS in the UK.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature. Protect from light, as epinephrine is light-sensitive and can oxidize (solution will turn pink or brown if oxidized and should be discarded).
Client information
Your pet has received a local anesthetic to numb a specific area for a procedure.
Important: The area may remain numb for a few hours. Prevent your pet from chewing, scratching, or rubbing the numb area, as they could cause severe self-injury without feeling it.
Monitor the injection site for any signs of excessive swelling, redness, or skin discoloration, and contact your veterinarian if you notice any unusual behavior.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.