Lidocaine is a widely used local anesthetic that temporarily numbs a specific body area. It is crucial for comfort during various medical and dental procedures. Many patients wonder how quickly lidocaine works and how long its numbing effects last. This article explains lidocaine’s action timeline and influencing factors.
Understanding Lidocaine’s Action
Lidocaine targets the nervous system at the injection site, preventing pain signals from traveling to the brain. It acts on voltage-gated sodium channels within nerve cell membranes, which transmit electrical impulses along nerves.
When injected, lidocaine temporarily blocks these sodium channels. This stops the influx of sodium ions into nerve cells, preventing the generation and conduction of nerve impulses. By interrupting these signals, lidocaine produces a localized numbing effect.
Onset and Duration of Numbness
Following an injection, lidocaine typically begins to work very quickly, with numbness often setting in within a few minutes. Many patients report feeling effects within 2 to 5 minutes, with some onset as rapid as 90 seconds.
The numbing effect of lidocaine injections generally lasts from 30 minutes to 3 hours. For example, in dental procedures, soft tissue numbness can last one to two hours, while deeper anesthesia might extend up to three hours. This duration is a general range, and individual experiences may vary.
Factors Affecting How Lidocaine Works
Several factors can influence both how quickly lidocaine takes effect and the overall duration of its numbing action.
Concentration
Higher lidocaine concentrations lead to faster onset and more prolonged numbing, allowing medical professionals to tailor the medication to specific procedural needs.
Epinephrine
The presence of epinephrine (adrenaline) impacts lidocaine’s performance. As a vasoconstrictor, it narrows blood vessels at the injection site. This constriction slows lidocaine absorption into the bloodstream, keeping it concentrated longer and extending its numbing effect.
Injection Site and Vascularity
The specific injection site and its vascularity also affect duration. Areas with rich blood supply absorb lidocaine more rapidly, potentially reducing its effect if epinephrine is not included. For example, absorption varies between highly vascularized areas like mucous membranes and less vascular areas like subcutaneous tissue.
Individual Metabolism
A person’s metabolism also influences how quickly the body processes and eliminates lidocaine. Individuals with faster metabolic rates might experience a shorter duration of numbness.
Common Uses and Patient Experience
Lidocaine injections are widely used in various medical and dental settings. They are administered for dental work like fillings or extractions, minor skin procedures such as stitching wounds or removing small lesions, and for joint injections.
Patients often report an initial stinging or burning sensation as lidocaine is injected. This sensation subsides quickly as the numbing effect spreads. Afterward, a feeling of heaviness, tingling, or pressure may develop in the treated area, leading to complete numbness.
As the lidocaine wears off, sensation gradually returns to the numbed area. Patients might experience tingling or a dull ache. Some soreness at the injection site is also possible.