How Long Does It Take for a Nerve Block to Get Out of Your System?

October 10, 2025 •

4 min read

While nearly 99% of patients undergoing total knee arthroplasty at specialized centers like HSS receive a nerve block, the national average is only about 1 in 4 [1.7.4]. So, how long does it take for a nerve block to get out of your system after a procedure?

Quick Summary

A nerve block's duration varies from hours to months, depending on the anesthetic used, its dose, and the type of block. The medication is metabolized and eventually eliminated, with sensation gradually returning.

Key Points

Duration Varies Greatly: A nerve block can last from a few hours to several months, depending on the type of block and medications used [1.2.2, 1.4.5].
Medication is Key: Short-acting anesthetics like lidocaine last a few hours, while long-acting ones like bupivacaine can last for over 12-24 hours [1.2.4, 1.9.1].
Dose and Additives Matter: Higher doses and the addition of substances like epinephrine can significantly prolong the block's effect [1.3.1, 1.3.4].
Continuous vs. Single Shot: A single injection lasts hours to a day, whereas a continuous catheter can provide pain relief for 2-3 days or more [1.4.3].
Gradual Return of Sensation: As the block wears off, you'll feel tingling or itching; it's vital to start oral pain meds before it's completely gone [1.2.2].
Protection is Crucial: The numbed area is susceptible to injury from pressure, heat, or cold until sensation fully returns [1.2.2].
Systemic Absorption: The anesthetic is eventually absorbed into the bloodstream and metabolized by the body, leading to the wearing-off effect [1.3.4].

What is a Nerve Block?

A nerve block is a medical procedure that involves injecting medication near a specific nerve or bundle of nerves to block pain signals [1.8.3]. It's a cornerstone of regional anesthesia, used for both surgical pain management and treating chronic pain conditions [1.11.3]. The primary goal is to "turn off" pain receptors in a targeted area, providing relief and, in some cases, diagnostic information to pinpoint the source of pain [1.8.3, 1.8.4]. Unlike general anesthesia, which renders a patient unconscious, a nerve block targets a specific region, such as an arm, leg, or the abdomen, reducing the need for systemic pain medications like opioids and their associated side effects [1.2.2, 1.5.1]. Anesthesiologists often use imaging guidance, such as ultrasound or fluoroscopy (a live X-ray), to precisely place the needle and deliver the medication, enhancing safety and effectiveness [1.5.1, 1.8.3].

How Nerve Blocks Work Pharmacologically

Nerve blocks function by interrupting the transmission of pain signals along nerve fibers. The medications used, primarily local anesthetics, prevent nerve cells from sending these signals to the brain [1.8.4]. They achieve this by blocking sodium channels within the nerve cell membrane. For a nerve impulse (an action potential) to propagate, sodium ions must rush into the cell. By blocking these channels, local anesthetics prevent this influx, thereby stopping the nerve from firing and transmitting the sensation of pain. Some injections also include corticosteroids, which are anti-inflammatory drugs that can reduce nerve irritation and swelling, potentially providing longer-term relief by allowing the nerve time to heal [1.8.1, 1.8.3].

Duration: How Long Until It's Out of Your System?

The answer to 'how long does it take for a nerve block to get out of your system?' varies widely. A single-injection nerve block for surgery can last anywhere from 3 to 36 hours [1.4.3, 1.2.3]. For example, a block for hand surgery might last 6-8 hours, while one for a total knee replacement could provide pain relief for 12-24 hours [1.2.4]. The specific timeframe depends on several key factors.

Factors Influencing Duration

Type of Medication: The specific local anesthetic used is a primary determinant of duration. Short-acting anesthetics like Lidocaine may last for 30 to 120 minutes, while long-acting agents like Bupivacaine and Ropivacaine can last for 180 to 360 minutes or longer [1.9.2].
Dose, Volume, and Concentration: The amount of medication administered plays a significant role. Higher doses and concentrations generally lead to a longer-lasting block [1.3.1, 1.3.2].
Use of Additives: Epinephrine is often added to the anesthetic solution. It causes vasoconstriction (narrowing of blood vessels) at the injection site, which slows the rate at which the medication is absorbed into the bloodstream, thereby prolonging the block's duration [1.3.4]. Other adjuvants like steroids (Decadron) or clonidine may also be used to extend the effect [1.4.1].
Location of the Block: Nerves in highly vascularized (rich in blood vessels) areas tend to have shorter block durations because the medication is carried away more quickly. Blocks on larger nerves, like the sciatic nerve, may last longer than those on smaller nerves [1.3.3].
Type of Block: A single injection provides relief for a limited time [1.4.4]. In contrast, a continuous nerve block, where a small tube (catheter) is placed near the nerve, can deliver medication for 2-3 days or even longer via a portable pump, offering extended pain control [1.2.4, 1.4.3]. For chronic pain, some blocks using steroids can provide relief for weeks to months [1.4.5].

Comparison of Common Anesthetics


Anesthetic Agent	Onset of Action	Typical Duration (Single Injection)	Common Use Case
Lidocaine	Fast (<2 minutes) [1.9.2]	Short (1-3 hours) [1.9.1]	Dental procedures, short surgical procedures [1.5.1, 1.9.1]
Mepivacaine	Intermediate	Intermediate (Varies with dose) [1.3.1]	Axillary brachial plexus blockade [1.3.1]
Bupivacaine	Slow (2-10 minutes) [1.9.2]	Long (up to 24+ hours) [1.9.3]	Post-operative pain, labor epidurals [1.9.2]
Ropivacaine	Slow	Long (Similar to Bupivacaine) [1.3.4]	Post-operative pain, good sensory/motor dissociation [1.3.4]

The Recovery Process: What to Expect as It Wears Off

As the nerve block wears off, sensation gradually returns to the affected area. This process is often accompanied by tingling, itching, or a feeling of coldness [1.2.2]. It is crucial to begin taking prescribed oral pain medication before the block wears off completely to manage the returning pain from the surgery or condition [1.2.2, 1.4.3].

While the area is numb, it is extremely important to protect it from injury. You may not be able to feel pain, pressure, or extreme temperatures [1.2.2]. If the block is in your arm or leg, the limb may feel heavy and weak, affecting your balance and increasing the risk of falls [1.2.1]. Always use slings, braces, or crutches as directed by your surgeon [1.2.2]. Common, temporary side effects as the block dissipates can include a hoarse voice, drooping eyelid, or mild breathing discomfort if the block was in the neck or shoulder area; these typically resolve within 24-48 hours [1.2.1].

When to Contact a Doctor

While most side effects are mild and transient, you should contact your doctor if you experience signs of infection (redness, swelling, fever), pain that is not controlled by your prescribed medication, or if numbness and weakness persist for more than a week [1.2.2]. Call 911 or go to the nearest emergency room if you experience symptoms like numbness around your mouth, a metallic taste, ringing in your ears, blurred vision, or a seizure, as these can be signs of a rare but serious reaction to the anesthetic [1.2.2].

Conclusion

A nerve block is an effective tool for managing pain, but the medication does not stay in your system permanently. For a typical single-shot surgical block, you can expect the numbness and pain relief to last from several hours to a full day, after which the anesthetic is metabolized by the body. The duration is influenced by a combination of the drug, dose, location, and technique used. Understanding what to expect during recovery is key to a smooth transition from the numbness of the block to managing post-procedural pain effectively.

For more information on regional anesthesia, you can visit the American Society of Regional Anesthesia and Pain Medicine (ASRA) website: https://www.asra.com/patients-public

Frequently Asked Questions

A single injection nerve block typically provides pain relief for 3 to 24 hours, depending on the specific anesthetic medication used, the dose, and the location of the injection [1.2.2, 1.5.1]. For chronic conditions, injections with steroids can provide relief for weeks to months [1.4.5].

As a nerve block wears off, you may feel tingling, itching, or cold sensations in the affected area. An increased awareness of pain is also a common sign that the medication is leaving your system [1.2.2].

Yes, a nerve block can last for 3 days or even longer if a continuous nerve block catheter is used. This involves a small tube placed near the nerve that is connected to a portable pump, delivering a steady stream of numbing medication [1.2.4, 1.4.3].

Yes, it is normal for some nerve blocks, particularly those using long-acting anesthetics like bupivacaine or for procedures like knee replacements, to last 24 hours or longer [1.2.4, 1.5.1]. In some cases, they can last up to 36 hours [1.2.3].

The primary factors are the type of local anesthetic used (short vs. long-acting), the dose and concentration of the medication, the addition of other drugs like epinephrine, and the specific location of the block on the body [1.3.1, 1.3.4].

You should start taking your prescribed oral pain medication before the nerve block completely wears off. This helps prevent a sudden onset of severe pain as sensation returns [1.2.2, 1.4.3].

You should call your doctor for signs of infection (fever, redness), severe shortness of breath, or if numbness/weakness lasts for more than a week. Go to the ER for symptoms like a metallic taste, ringing in the ears, blurred vision, or seizures [1.2.2].