Xylocaine is a brand name for lidocaine, a local anesthetic used to numb specific areas of the body before medical, dental, and surgical procedures. It works by blocking nerve signals in the tissue where it’s applied or injected, preventing you from feeling pain in that area. Beyond numbing, Xylocaine also has a lesser-known role in emergency medicine: treating dangerous heart rhythm problems.
How Xylocaine Works
Lidocaine, the active ingredient in Xylocaine, stabilizes nerve cell membranes by blocking the tiny channels that allow electrical signals to travel along nerves. When those signals can’t move, the nerve can’t transmit pain. This is why the effect is local rather than whole-body: the drug only affects the nerves in the tissue it reaches directly.
The same property that makes lidocaine useful for pain also makes it useful for the heart. Heart cells rely on those same electrical channels to coordinate their rhythm. When the heart’s electrical system misfires, lidocaine can help restore order by calming overactive signals in cardiac tissue.
Common Uses in Medical and Dental Procedures
Xylocaine’s FDA-approved uses span a wide range of procedures. The most familiar is probably dental work. When your dentist injects a numbing agent before a filling or extraction, it’s often lidocaine. For dental injections, the onset of numbness averages less than two minutes, though the deep tooth-level numbness (called pulp anesthesia) from a standard 2% dental injection lasts only about five minutes. Soft tissue numbness lasts considerably longer.
Outside the dentist’s chair, Xylocaine is used for:
- Infiltration anesthesia: injecting directly into the skin or tissue around a wound, incision, or biopsy site
- Peripheral nerve blocks: numbing a specific nerve or group of nerves to block pain in a larger region, such as the arm (brachial plexus block) or the space between ribs (intercostal block)
- Epidural blocks: injecting into the space around the spinal cord for pain relief during labor, abdominal surgery, or chest procedures
- Intravenous regional anesthesia: numbing an entire limb by injecting lidocaine into a vein while a tourniquet keeps the drug in that limb
- Obstetrical pain relief: paracervical and pudendal nerve blocks used during labor and delivery
There are also specialty applications. A 4% sterile solution can be injected near the eye for ophthalmic surgery or sprayed into the throat before procedures like bronchoscopy or intubation, where a tube needs to pass through the airway without triggering a gag reflex.
Use in Heart Rhythm Emergencies
Xylocaine given intravenously is one of the medications used during cardiac arrest when the heart is in a dangerously abnormal rhythm, such as ventricular fibrillation or pulseless ventricular tachycardia. In the 2025 American Heart Association guidelines, lidocaine remains an option alongside amiodarone during advanced cardiac life support.
A large randomized trial found that both amiodarone and lidocaine improved survival to hospital admission compared to placebo, though neither showed a clear advantage in survival to hospital discharge. Current evidence can’t definitively say one is better than the other. For a specific type of abnormal rhythm called polymorphic ventricular tachycardia, often triggered by a heart attack, lidocaine may be used alongside other treatments and defibrillation. However, for stable wide-complex tachycardia (where the patient still has a pulse and blood pressure), lidocaine appears less effective than other antiarrhythmic options.
Topical and Over-the-Counter Forms
Lidocaine isn’t only available by injection. Prescription topical forms include creams, gels, and patches. The 5% lidocaine patch is specifically approved in the U.S. to treat postherpetic neuralgia, the persistent nerve pain that can follow a shingles outbreak. It delivers the drug through the skin directly over the painful area.
A 4% lidocaine patch is available over the counter for general pain relief. It’s worth knowing that no published clinical data currently compare the effectiveness of the OTC 4% patch to the prescription 5% patch, so the evidence base for the lower-strength version is limited. Topical lidocaine creams and sprays are also widely available for minor skin irritations, sunburn, and insect bites.
Available Concentrations
Xylocaine comes in several concentrations depending on the procedure. Injectable solutions typically range from 0.5% to 2% for most routine uses, with a 4% sterile solution reserved for airway procedures and eye surgery. The concentration your provider chooses depends on the location being numbed, how deep the numbness needs to reach, and how long the procedure will take. Some formulations include epinephrine, which constricts blood vessels near the injection site, slowing absorption and making the numbing effect last longer.
Potential Side Effects
At normal doses, Xylocaine’s side effects are typically mild and limited to the injection site: temporary stinging, swelling, or bruising. The numbness itself can feel strange, and you may accidentally bite your lip or tongue after dental work before sensation returns.
The more serious concern is local anesthetic systemic toxicity, or LAST, which happens when too much lidocaine enters the bloodstream. This is rare but can occur if a dose is too high or if the drug is accidentally injected into a blood vessel. Early warning signs include a metallic taste in the mouth, numbness around the lips, ringing in the ears, confusion, and slurred speech. Seizures are the most common serious sign. In severe cases, LAST can affect the heart, causing a dangerously slow or fast heart rate, a drop in blood pressure, or cardiac arrest.
Providers minimize this risk by using the lowest effective dose, aspirating (pulling back on the syringe) before injecting to make sure the needle isn’t in a blood vessel, and monitoring you during and after the procedure. The risk is higher with nerve blocks that require larger volumes of the drug or injections near major blood vessels.