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Lidocaine, also sold under the brand name Xylocaine®, is a local anesthetic used to block pain sensation during medical procedures. In horses, lidocaine may also be administered intravenously to provide systemic analgesic and anti-inflammatory effects and support gastrointestinal motility.
Systemic lidocaine is often administered as a continuous-rate infusion (CRI), allowing veterinarians to maintain therapeutic drug concentrations over an extended period. This approach can provide ongoing pain control and gastrointestinal support for the duration of a procedure or treatment.
Keep reading to learn how systemic lidocaine works in horses, its common clinical uses, potential benefits and risks, recommended administration methods, and important considerations for horse owners, trainers, and veterinarians.
Intravenous Lidocaine for Horses
Although more commonly known as a local anesthetic, lidocaine is also used systemically (to the whole body) in veterinary practice.
Veterinarians use intravenous lidocaine to help provide analgesia (pain control), improve intestinal motility during and after surgery, and as an anti-inflammatory agent. [1] Providing lidocaine during surgery can also reduce the amount of anesthetic drugs necessary for the procedure. [2]
The most common brand name of lidocaine is Xylocaine®. [3] There are also several generic products available for veterinary use.
These products are not approved for intravenous use in horses, but veterinarians can use them in an off-label manner. This practice is acceptable in veterinary medicine, as drug companies may not have tested and approved the drug for all species or applications. However, the drug company may not warranty the drug if there is an adverse reaction.
Available Forms
Veterinarians administer systemic lidocaine intravenously (IV), or directly into a blood vessel. Given this, formulations of lidocaine for systemic use are typically sterile liquids.
Veterinarians often mix the lidocaine liquid into a bag of fluids to provide a constant rate infusion (CRI). This process allows the veterinary team to provide a steady dose of lidocaine to the horse during long procedures, such as surgeries. [3]
Xylocaine® is the brand name formulation, produced by Aspen Pharmacare Canada for equine use. Generic products are labeled as Lidocaine HCl 2% injection for Animal Use. These products are approved for tissue injection, not intravenous injection. Veterinarians may inject them intravenously in an off-label manner.
Drug Class: Sodium Channel Blockers
Lidocaine is primarily a sodium channel blocker, although it can have effects on other types of channels throughout the body. Having a wide range of effects helps it maintain analgesia (pain control) effectively and prolongs its effects after administration of the drug stops. [2]
Other sodium channel blockers include: [1]
- Quinidine
- Procainamide
- Mexiletine
Mechanism of Action
Sodium channels are present in numerous tissues throughout the body, including: [4]
- Nerves
- Muscle fibers
- Skin
- Kidneys
Sodium channels allow a sodium ion to pass through a cell membrane, often producing an electrical charge in the process. This electricity can travel to other cells, activating their sodium channels and propagating the signal to other tissues in the body. [4]
Nerves use sodium channels to send signals to the brain about touch, pain, and other sensations. Muscles respond to this signal by contracting, allowing the nerves to produce movement. [4]
Muscle fibers with sodium channels are present throughout the body, including the heart and intestines. In the heart, lidocaine inhibits (blocks) sodium channel opening in cardiac muscle fibers. [3] This prevents the electrical signal from transmitting to the fiber, preventing its contraction. [3] This slows the heart rate and helps prevent tachycardia (abnormally fast heart rate).
In the intestine, smooth muscle fibers respond to sympathetic nervous signals by reducing their contractility. The sympathetic nervous system activates during times of stress to reduce energy use by the intestines. By blocking sympathetic nerve signals, lidocaine may help maintain intestinal motility, even in the face of stressful events like surgery or certain types of colic that slow motility, like enteritis. [3]
Uses in Horses
Lidocaine has many potential uses in veterinary medicine: [3]
- Local anesthetic injected around nerves
- Topical anesthetic applied to the skin
- Treatment of cardiac arrhythmias
- Pain control during surgical procedures
- Increasing intestinal motility
Systemic lidocaine is primarily used for providing pain control during surgical procedures, whether the horse is awake or under general anesthesia. It can be used in combination with anesthetic agents such as ketamine or xylazine. [2]
Veterinarians may administer IV lidocaine during anesthesia to reduce the amount of other anesthetic drugs required for a procedure. [2] It can also be used to manage neuropathic (nerve-associated) pain from traumatic injuries or surgeries. [3]
In emergency medicine, lidocaine is used to treat life-threatening heart arrhythmias called ventricular tachycardia and ventricular premature complex. [3] This allows the heart rhythm to stabilize while the underlying cause of heart disease is managed.
It can also increase intestinal motility. Veterinary surgeons may use lidocaine to decrease the risk of postoperative ileus in equine patients. Ileus refers to decreased or absent motility of the intestinal tract and is a common side effect of anesthesia and surgery in horses. [3]
Due to its pain control properties and its effect on intestinal motility, lidocaine is commonly used for colic surgeries.
Administration Routes
Systemic lidocaine is administered intravenously (into a vein). Depending on the length of the procedure or the reason for administering lidocaine, veterinarians may administer the medication as part of a constant rate infusion. [3]
This requires placement of an intravenous catheter that remains within the vessel for the duration of the procedure.
Dosage
The dose of lidocaine provided depends on the reason for administration. Usually, a larger bolus (volume of fluid) is given at the start of a treatment, then smaller doses are given through a constant rate infusion for the remainder of the treatment. [3]
The smaller doses maintain the drug’s concentration in the blood over a prolonged period for a consistent effect. [3] A CRI also allows the veterinarian to adjust the dose of lidocaine if the treatment is no longer effective.
Storage
Injectable lidocaine should be stored at room temperature between 15 and 30ºC (59 to 86ºF). Avoid freezing. [3]
Safety Warnings & Precautions
Lidocaine is a safe drug when administered slowly in correct doses. Serious adverse reactions are rare. [3]
Monitoring
During surgical procedures, horses administered lidocaine are monitored with an electrocardiogram that identifies their cardiac rhythm. [3] This allows veterinarians to identify any changes in heart electrical activity that may be life-threatening.
The veterinary team also monitors the horse closely for signs of toxicity, such as muscle tremors or low blood pressure. Identifying these signs early allows them to adjust the dose of lidocaine to prevent more serious complications from occurring. [3]
Contraindications
Contraindications refer to circumstances where a drug should be avoided or used with caution.
Lidocaine should not be used in horses with a previous hypersensitivity to local anesthetics.
Other contraindications warranting cautious use of lidocaine include: [3]
- Animals with cardiac arrhythmias causing bradycardia (slow heart rate)
- Liver disease
- Congestive heart failure
- Hypotension (low blood pressure)
- Severe respiratory compromise
Side Effects
The side effects of systemic lidocaine are dose-dependent, meaning that more side effects occur with an increasing amount of medication. By adjusting the amount of medication delivered, the veterinarian can alter the severity of the side effects.
Common side effects include: [3]
- Drowsiness
- Uncoordinated movement (ataxia)
- Muscle tremors
- Seizures
- Heart arrhythmias
The most significant side effect of lidocaine administration is hypotension (low blood pressure). Rapid administration of high doses of lidocaine can result in low blood pressure, which may lead to collapse. To avoid this side effect, veterinarians give lidocaine slowly over several seconds to minutes. [3]
Acute Toxicity (Overdose)
Lidocaine toxicosis most commonly causes seizures and hypotension. These side effects resolve as lidocaine is metabolized by the body and excreted. [2]
Sedation or anti-seizure medications may be necessary to control seizures for the safety of the horse and its handlers. [2] Horses with severe hypotension may require fluid therapy or other medications to restore normal blood pressure. [3]
Drug Interactions
Systemic lidocaine may interact with other drugs in the horse’s bloodstream. Typically, these interactions affect lidocaine’s metabolism (breakdown in the body). This can lead to increased effects of lidocaine and may predispose the horse to toxicosis. [3]
Drugs that may increase the risk of lidocaine toxicosis include: [3]
- Antiarrhythmic medications such as quinidine and procainamide
- Cimetidine
- Propranolol
Administration of anti-epileptic medications such as phenobarbital or phenytoin may decrease lidocaine levels, requiring additional administration to maintain efficacy. [3]
Regulatory Status & Legal Considerations
There are injectable forms of lidocaine available as a local anesthetic for veterinary medicine, but there are no approved injectable forms for systemic administration. [5][6] Veterinarians can use human-approved intravenous products when administering systemic lidocaine, or use veterinary-approved lidocaine formulations intravenously. In both cases, the use of these medications is off-label, meaning the drug has not been tested by the drug company for that use scenario.
Off-label use of medication is valid practice in veterinary medicine, as many useful drugs have not been tested by the drug companies for their efficacy and safety in veterinary species, or via all potential administration routes. When using drugs off-label, veterinarians use research studies, personal experience, and other sources to determine the ideal dose and duration of treatment for their patients.
Since the drug company has not tested the drug specifically in horses or for intravenous use, they often do not warrant their product for side effects or adverse reactions. Owners should be aware of this caveat when their veterinarian prescribes or administers drugs in an off-label manner to their horse.
Status in Competition
Use in equine competition is generally restricted because lidocaine is classified as a local anesthetic and pain-masking agent. [7] Regulatory bodies prohibit medications that could alter performance or allow a horse to compete despite an underlying injury or disease.
Horses receiving lidocaine must typically observe an appropriate withdrawal period before competition to avoid positive drug tests and ensure compliance with medication regulations.
Withdrawal recommendations vary among organizations and may depend on the dose, route of administration, and timing of treatment, so competitors should consult the rules of their governing body and their veterinarian before entering a treated horse in competition.
Frequently Asked Questions
Here are some frequently asked questions about systemic lidocaine in horses:
Systemic lidocaine in horses refers to lidocaine given intravenously so it can act throughout the body rather than only numbing one local area. Although lidocaine is best known as a local anesthetic, veterinarians may use it systemically for pain control, anesthesia support, inflammation modulation, heart rhythm stabilization, and gastrointestinal motility support. It is typically administered in a hospital or clinical setting under veterinary supervision.
Lidocaine is given intravenously to horses when veterinarians want systemic effects such as pain relief, reduced anesthetic requirements, or support for intestinal motility. It is commonly used as part of balanced anesthesia protocols and may be given during or after surgery. Intravenous administration allows the veterinary team to control dosing closely and adjust treatment based on the horse's response.
Systemic lidocaine in horses may be used for pain control during awake or anesthetized procedures, neuropathic pain, certain life-threatening heart arrhythmias, and reduced intestinal motility after surgery. It is especially associated with colic surgery because it can support pain control and may help decrease the risk of postoperative ileus. Veterinarians may also use it to reduce the amount of other anesthetic drugs needed during a procedure.
Systemic lidocaine works in horses primarily by blocking sodium channels, which help nerves, muscles, and other tissues transmit electrical signals. By affecting nerve signaling, lidocaine can reduce pain transmission. Its effects on heart muscle and intestinal smooth muscle also help explain why it may be used for certain arrhythmias and to support gastrointestinal motility.
Systemic lidocaine can act as a pain medication for horses when administered intravenously by a veterinarian. It has analgesic properties and is often used alongside other medications as part of a multimodal pain management plan. This approach can be useful during painful procedures, surgery, or recovery from certain injuries.
Systemic lidocaine is not a traditional anti-inflammatory drug like an NSAID or corticosteroid. However, it may have anti-inflammatory effects that contribute to its clinical benefits in horses. Veterinarians may consider these effects when using lidocaine as part of a broader treatment plan, especially in critically ill or surgical patients.
Lidocaine can be used during equine anesthesia as part of a balanced anesthetic protocol. Intravenous lidocaine may reduce the amount of inhalant or injectable anesthetic drugs required for a procedure. This can help veterinarians manage anesthesia more precisely while also providing systemic pain control.
Lidocaine may be used after colic surgery in horses because it can support pain control and intestinal motility. Postoperative ileus, or reduced intestinal movement, is a common concern after anesthesia and abdominal surgery in horses. By helping maintain motility and contributing to analgesia, lidocaine can be a useful part of postoperative management in selected cases.
A lidocaine continuous-rate infusion, or CRI, is a method of giving lidocaine at a steady rate through an intravenous catheter. This helps maintain more consistent drug concentrations in the bloodstream over time. Veterinarians often use a CRI during longer procedures or treatments when sustained effects are needed.
Systemic lidocaine is administered to horses intravenously, usually through a catheter placed into a vein. Veterinarians may give an initial bolus followed by a lower continuous-rate infusion to maintain the desired effect. Because incorrect dosing or rapid administration can cause serious adverse effects, systemic lidocaine should only be given under veterinary direction.
Side effects of systemic lidocaine in horses are generally dose-dependent, meaning they become more likely as blood concentrations increase. Possible signs include drowsiness, ataxia, muscle tremors, seizures, heart rhythm changes, and low blood pressure. Rapid administration of high doses can cause hypotension and may lead to collapse.
Signs of lidocaine toxicity in horses may include muscle tremors, incoordination, seizures, low blood pressure, and cardiovascular complications. Toxicity is more likely if lidocaine is given too quickly, at an excessive dose, or in a horse with health issues that affect drug metabolism or cardiovascular function. Veterinary teams monitor treated horses closely so dosing can be adjusted before serious complications develop.
Systemic lidocaine is generally considered safe for horses when it is administered slowly, at appropriate doses, and with veterinary monitoring. Serious adverse reactions are rare when the drug is used correctly. Safety depends on the horse's condition, the dose, the rate of administration, and whether the horse has contraindications such as liver disease, severe heart disease, hypotension, or respiratory compromise.
Some horses should not receive systemic lidocaine, or should receive it only with extra caution, depending on their medical history. Lidocaine should be avoided in horses with known hypersensitivity to local anesthetics. Caution is also warranted in horses with bradycardia-associated arrhythmias, liver disease, congestive heart failure, hypotension, or severe respiratory compromise.
Systemic lidocaine can interact with other medications by changing how lidocaine is metabolized or by increasing the risk of toxicity. Drugs such as quinidine, procainamide, cimetidine, and propranolol may increase toxicity risk. Anti-epileptic medications such as phenobarbital or phenytoin may decrease lidocaine levels, so owners should tell their veterinarian about all medications and supplements their horse has received.
Systemic lidocaine is used in horses as an off-label medication because injectable lidocaine products are approved as local anesthetics, not specifically for systemic administration in horses. Off-label drug use is a common and valid part of veterinary medicine when guided by research, clinical experience, and professional judgment. Horse owners should understand that off-label use requires careful veterinary dosing and monitoring.
Systemic lidocaine is generally restricted in horse competition because it is classified as a local anesthetic and pain-masking agent. These effects could alter performance or allow a horse to compete despite pain, injury, or disease. Horses treated with lidocaine typically need an appropriate withdrawal period before competition, and requirements vary by governing body.
How long lidocaine stays in a horse's system depends on the dose, treatment duration, route of administration, and the individual horse's metabolism. The time needed for competition compliance may be longer than the drug's obvious clinical effects. Competitors should consult their veterinarian and the rules of their governing organization before entering a horse that has received lidocaine.
Horse owners should not give systemic lidocaine themselves unless they are acting under direct veterinary instruction and within applicable laws. Systemic lidocaine is a prescription-only medication that must be dosed carefully and administered intravenously. Because overdose, rapid administration, and drug interactions can cause serious complications, treatment belongs in the hands of a licensed veterinarian.
Horses receiving systemic lidocaine are typically monitored for heart rhythm, blood pressure, coordination, tremors, sedation, and other signs of adverse effects. An electrocardiogram may be used to assess cardiac electrical activity during treatment. Close monitoring allows the veterinary team to adjust or stop the infusion if signs of toxicity or cardiovascular effects appear.
Summary
Systemic lidocaine is an intravenous medication used in horses for its analgesic, anti-inflammatory, and gastrointestinal effects.
- Systemic lidocaine is administered intravenously rather than injected locally to numb tissues
- It is commonly used to help manage pain and support recovery in horses during surgical procedures
- The drug is often delivered as a continuous-rate infusion (CRI) in equine hospitals
- Potential side effects include muscle tremors, ataxia, agitation, and, in severe cases, seizures or cardiovascular complications
- Lidocaine use is regulated in equestrian competition and may require a withdrawal period before a horse can compete
References
- Cole. C. et al. Eds.Equine Pharmacology. 1st ed. John Wiley & Sons, Ltd. 2014.
- Doherty. T. et al. Eds. Manual of Equine Anesthesia and Analgesia. 1st ed. Wiley. 2022.
- Plumb. D. C. Veterinary Drug Handbook. Pocket 7. ed. Wiley Blackwell, Ames, Iowas. 2011.
- Hernandez. C. M. and Richards. J. R. Physiology, Sodium Channels. StatPearls. 2026.
- Drug Product Database. Health Canada.
- Animal Drugs @ FDA. Food and Drug Administration. 2025.
- 2026 Prohibited Substances List. FEI. 2026.
