Understanding Local Anesthetics
Local anesthetics are medications that block nerve signals to prevent or relieve pain in a specific area. They work by inhibiting voltage-gated sodium channels, preventing the transmission of pain signals to the brain. Lidocaine and benzocaine are two widely used topical anesthetics with similar mechanisms but different properties.
All About Lidocaine
Lidocaine, an amino amide local anesthetic discovered in the 1940s, is metabolized primarily in the liver. It is available in various forms, including injections, creams, gels, patches, and sprays. Its onset of action for topical application is typically within 3 to 5 minutes, providing relief for about 35 to 90 minutes. Due to its higher potency and longer duration, lidocaine is often used for minor surgical procedures, dental work, managing nerve pain from shingles, treating hemorrhoids, and as a lubricant during medical procedures.
All About Benzocaine
Benzocaine is an ester local anesthetic, metabolized rapidly in the plasma by pseudocholinesterase. This rapid breakdown results in a shorter duration of action. Benzocaine is known for its very rapid onset, often taking effect within 15 to 30 seconds, but its effects last only 5 to 15 minutes. It is commonly found in OTC products for temporary relief of pain on mucous membranes and skin. Uses include soothing mouth and gum irritation, relieving pain from minor skin irritations and sunburn, and as an ingredient in sore throat products.
Head-to-Head Comparison: Which is Stronger?
Comparing equal concentrations, lidocaine is considered a stronger and more potent local anesthetic than benzocaine. Studies indicate that a lower concentration of lidocaine can achieve a similar effect to a higher concentration of benzocaine. The choice between them depends on the need for quick onset versus longer-lasting and deeper anesthesia.
Comparison Table
| Feature | Lidocaine | Benzocaine |
|---|---|---|
| Potency | Higher; considered stronger | Lower; requires higher concentration for similar effect |
| Anesthetic Class | Amide | Ester |
| Onset of Action | Slower (3-5 minutes for cream) | Faster (15-30 seconds for spray) |
| Duration of Action | Longer (35-90 minutes) | Shorter (5-15 minutes) |
| Metabolism | Liver | Plasma (by pseudocholinesterase) |
| Common Forms | Cream, Gel, Patch, Injection, Spray | Gel, Spray, Ointment, Lozenge |
Side Effects and Safety Considerations
Both medications can cause minor side effects like stinging or redness at the application site. Using them together is not advised due to increased risk of side effects such as dizziness or irregular heartbeat.
Methemoglobinemia, a serious blood condition where oxygen transport is reduced, is a risk with both, but particularly with benzocaine. In 2018, the FDA warned against using OTC oral benzocaine products in children under 2 due to this risk.
Conclusion
Lidocaine is the more potent anesthetic in terms of strength and duration, making it suitable for procedures needing sustained pain relief. Benzocaine offers a faster onset and is widely available in OTC products for rapid, short-term relief of surface pain. The selection depends on the required speed, duration, and depth of anesthesia, as well as considering their safety profiles, especially the higher risk of methemoglobinemia with benzocaine.
For more information on the risks associated with benzocaine, you can review safety communications from the U.S. Food and Drug Administration.
