What is stronger, benzocaine or lidocaine? A pharmacological comparison

October 10, 2025 •

3 min read

While both are local anesthetics used for pain relief, a study showed that a 20% benzocaine solution was as effective as a 5% lidocaine solution for numbing prior to a needle insertion. This example highlights that potency isn't just about concentration but a complex interplay of chemical properties, leading to the crucial question: what is stronger, benzocaine or lidocaine?.

Quick Summary

Benzocaine provides a fast onset but shorter duration, while lidocaine is generally more potent and lasts longer, though both can be equally effective for superficial pain relief. The choice depends on the specific application and safety considerations.

Key Points

Lidocaine is more potent: For the same concentration, lidocaine is technically a stronger local anesthetic than benzocaine.
Benzocaine has a faster onset: Benzocaine often starts numbing faster, in seconds, making it effective for quick surface-level pain relief.
Lidocaine lasts longer: The numbing effect of lidocaine generally lasts for a longer duration than that of benzocaine.
Methemoglobinemia is a risk: Both can cause this serious blood disorder, leading the FDA to issue warnings against using oral benzocaine products in children under 2.
Chemical class affects risks: Benzocaine is an ester, with a higher potential for allergic reactions, while lidocaine is an amide and less likely to cause an allergic response.
Applications differ: Benzocaine is typically used for minor, superficial pain (e.g., toothache, minor cuts), whereas lidocaine is used for a broader range of applications, including more complex medical procedures.

Introduction to Local Anesthetics

Local anesthetics are a class of medications designed to block nerve signals temporarily, causing a numbing sensation in a specific area. Benzocaine and lidocaine are two of the most common topical local anesthetics used today. While they work through a similar mechanism—blocking sodium channels to prevent nerve signal transmission—their chemical structure leads to key differences in potency, speed, and duration of action. Understanding these distinctions is crucial for proper and safe use, as the stronger anesthetic isn't always the best choice.

Chemical Differences and Their Impact

The fundamental difference between benzocaine and lidocaine lies in their chemical class, which influences how they are processed by the body and their potential for side effects.

Benzocaine: As an ester-type anesthetic, benzocaine is metabolized by plasma esterases in the bloodstream. This process can create metabolites that have a higher potential for causing allergic reactions. Benzocaine's poor water solubility also means it doesn't penetrate deeply into tissues, making it ideal for surface-level application.
Lidocaine: As an amide-type anesthetic, lidocaine is metabolized in the liver. This chemical structure makes allergic reactions much less common than with ester-type anesthetics. Lidocaine is more versatile and can be formulated for deeper tissue penetration, including injections and patches, in addition to topical use.

Potency, Onset, and Duration of Action

When comparing potency, lidocaine is technically considered stronger than benzocaine. However, the practical effectiveness depends on the formulation and intended use. Benzocaine and lidocaine also differ markedly in their speed and duration of effect.

Potency: For the same concentration, lidocaine is generally considered more potent. Studies comparing common topical concentrations, such as 20% benzocaine versus 5% lidocaine for numbing before needle insertion, showed comparable pain relief.
Onset: Benzocaine typically acts faster than lidocaine. Its effect can be felt quickly, while a lidocaine cream may take a few minutes to work. This fast action makes benzocaine a common choice for quick relief of minor mouth or skin irritation.
Duration: Lidocaine generally provides a longer-lasting numbing effect than benzocaine.

Common Applications

Both anesthetics are used for a variety of conditions, but their different properties make them better suited for specific applications. Benzocaine is often found in over-the-counter products for oral pain relief, sore throats, and minor skin irritations. Lidocaine is available in both over-the-counter and prescription forms and is used for topical anesthesia for minor procedures, relief from hemorrhoid pain, anal itching, shingles, and in patches for nerve pain. Lidocaine is also used in systemic injections for cardiac rhythm problems.

Safety Considerations and FDA Warnings

The most significant safety concern for both medications is methemoglobinemia, a serious blood disorder. Due to this risk, the U.S. Food and Drug Administration (FDA) has issued specific warnings for benzocaine. The FDA advises against using over-the-counter oral products containing benzocaine for infants and children under 2 years old, particularly for teething pain. In cases of accidental exposure, signs such as pale, gray, or blue-colored skin, shortness of breath, and fatigue require immediate medical attention.

Lidocaine Misuse Risks: Misuse of lidocaine can lead to serious complications, including systemic toxicity. The FDA has also warned against using topical lidocaine to treat teething pain. For safe usage guidelines on benzocaine, consult the {Link: FDA's safety information on benzocaine-containing products https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/safety-information-benzocaine-containing-products}.

Comparison: Benzocaine vs. Lidocaine


Feature	Benzocaine	Lidocaine
Potency	Lower potency, especially in comparison to lidocaine at similar concentrations.	Generally higher potency.
Onset of Action	Rapid (seconds to minutes).	Slower (minutes).
Duration of Action	Shorter (10-15 minutes).	Longer (35-40 minutes or more).
Chemical Class	Ester-type local anesthetic.	Amide-type local anesthetic.
Allergic Potential	Higher, due to metabolites.	Lower.
Safety Concerns	Higher risk of methemoglobinemia in young children; FDA warnings in place.	Risk of systemic toxicity with misuse (overuse, covering treated areas).
Availability	Primarily OTC.	OTC and prescription.

Conclusion: Which is Stronger and When to Use Each?

When comparing intrinsic potency, lidocaine is the stronger local anesthetic. Benzocaine offers a faster onset for quick, short-lived relief on mucosal surfaces. Lidocaine, with its greater potency and longer duration, is better suited for situations requiring a more profound and sustained numbing effect. The choice between the two depends on the specific need, application site, and safety considerations, particularly regarding methemoglobinemia risk, which the FDA has highlighted for benzocaine use in infants. Always follow product directions and consult a healthcare professional for guidance on the most appropriate anesthetic for your condition.

Frequently Asked Questions

Both are safe when used as directed, but come with significant risks if misused. The FDA has issued warnings against using benzocaine in infants due to the risk of methemoglobinemia, a life-threatening blood disorder. Always consult a healthcare professional to determine the safest option for your specific situation.

No, it is not recommended to use benzocaine and lidocaine together. Both belong to the same class of drugs and using them simultaneously can increase the risk of side effects such as severe dizziness, drowsiness, or an irregular heartbeat.

Both can be effective for oral pain. Over-the-counter benzocaine gels and liquids provide rapid, short-term relief. However, depending on the severity and specific issue, a dentist might use a more potent lidocaine product during a procedure. Always follow package instructions and consult a dentist for persistent pain.

Yes, lower-concentration topical lidocaine products (such as patches, creams, and gels) are available over-the-counter for pain relief. Higher-concentration formulas and injectable forms are available by prescription only.

Benzocaine typically has a faster onset of action, often providing a numbing effect within seconds. Lidocaine's numbing effect takes a few minutes to set in.

Methemoglobinemia is a rare but serious blood disorder that can be caused by both benzocaine and lidocaine. It reduces the amount of oxygen carried by red blood cells, with severe cases being life-threatening. Symptoms can include pale, gray, or blue-colored skin, shortness of breath, and confusion.

The FDA has issued warnings advising against the use of both benzocaine and lidocaine for teething pain in infants. Due to the risk of methemoglobinemia and absorption issues in young children, alternative methods, such as using a chilled teething ring or massaging the gums with a finger, are recommended instead.