Clinicians are increasingly using topical anesthetics (topical lidocaine numbing cream products) to decrease the pain associated with minimally invasive dermatologic, aesthetic, needle insertion, cannulation and laser procedures (among others).
Numerous topical lidocaine numbing cream products are available, but comprehensive studies are lacking regarding their relative safety and appropriate dermatologic uses.
Topical Lidocaine Numbing Cream products play an integral role in cutaneous anesthesia by providing patient comfort with minimal side-effects. Careful attention should be paid to the particular anatomic location, the total surface area covered, the concentration of anesthetic ingredient(s), mechanisms of action of additional pharmacologic ingredients and the duration of anesthetic skin contact.
Topical lidocaine numbing cream anesthetics decrease pain during superficial cutaneous procedures. As the number of in-office dermatologic procedures continues to grow, clinicians will benefit from awareness of the indications, pharmacologic mechanisms, appropriate methods of application, and safety profiles of the currently available prescription and over-the-counter (OTC) topical anesthetics.
Mechanism of Action:
Once inside the dermis, ester and amide anesthetics possess the same mechanism of action. The anesthetic binds the voltage-gated sodium ion channel of the free nerve endings and blocks sodium influx. The blockade of sodium influx inhibits nerve cell depolarization and prevents propagation of nerve cell impulses along the nerve. Meechan JG. Intraoral topical anesthesia. Periodontal 2000 2008;46:6 – 79
Clinical Use and Application:
Application of a topical lidocaine numbing cream anesthetic before superficial dermal instrumentation procedures can help to relieve pain and anxiety related to anticipated pain. Patients can apply the topical lidocaine numbing cream before arriving at the office, assuming they have proper instructions on its safe application.
Safe application involves gently washing the area to be treated with a mild cleanser and water to eliminate contaminants (e.g., makeup, dirt) that could hinder the absorption or efficacy of the anesthetic. The product should be applied in a thin layer (approximately 1/8”) and at an approximate volume of 0.75 – 2.0 milliliters per 1”x1” square. The volume will be determined based on factors such as: location, skin type, level of procedural aggressiveness, known pain tolerance of patient and known patient sensitivity to active ingredient.
Depending upon the anesthetic used, the product is left in place for 20 to 60 minutes. Occlusion with plastic wrap or massaging the cream into the skin (or both) may achieve quicker onset of action, if necessary. FDA suggests that occluding may also lead to an increased risk of toxic systemic absorption. Immediately preceding the procedure, the material is removed with dry gauze, and the skin is wiped clean with water-dampened gauze or normal preparation procedures.
Topical lidocaine numbing cream products are routinely used for (among others) the following procedures:
Potential for Complications:
Improper application of topical anesthetic preparations such as benzocaine, lidocaine, prilocaine and tetracaine may cause serious complications. Complications can come in two primary forms: central nervous system toxicity and cardio-toxicity. Complications can be caused by prolonged application, use of inappropriately high concentrations (30% and higher compounded products), and application to overly large surface areas.
The risk of systemic absorption can be increased when powerful drivers such as DMSO are included to promote penetration. DMSO is also used to deliver small molecules into the blood. There is a trend among many compound pharmacies to increasingly add DMSO in an effort to increase the speed to onset of anesthetic action. When DMSO is used as a driver to deliver anesthetics, it may be appropriate to monitor the patient for symptoms related to systemic toxicity.
Another risk of using compounded topical anesthetics supplied in multi-use containers is the risk of cross contamination. This can occur either from improper manufacture when the environment is not sanitary or more often the case, when multiple uses cause contaminants to enter the multi-use container. A potential side effect of this occurrence can be in the form of medico-legal risk and the drawing of unwanted investigation into the cause of the cross contamination. Both State and Federal laws are clear that when procuring compounded medications, the requirement is one order for one patient in limited amounts prescribed by a licensed clinician.
Adverse Events Warning Signs:
There is some degree of inherent risk associated with the use (and more appropriately misuse) of topical anesthetics. In general, the central nervous system is more susceptible to the pharmacologic actions of local anesthetics than is the cardiovascular system. Wagman IH, De Jong RH, Prince DA. Effects of lidocaine on the central nervous system. Anesthesiology 1967;28:155 – 72
The initial symptoms of anesthetic-induced toxicity include (among others) lightheadedness, circumoral numbness, diplopia, slurred speech, fine tremors, metallic taste and tinnitus.
Many adverse reactions also appear to be related to the inclusion of epinephrine or the driver, DMSO within the anesthetic mixture. Mehra P, Caiazzo A, Maloney P. Lidocaine toxicity. Anesth Prog 1998;45:38 – 41
In an effort to reduce the risks (and improve efficacy) associated with the application of topical anesthetics, you may choose to adhere to some or all of the following suggestions:
Management of Toxicity:
When administered with the necessary reasonable precautions, it is unlikely that you will experience severe adverse events when using appropriately concentrated topical lidocaine numbing cream and related anesthetics.
In the unlikely event you do, rapid recognition of and quick response to anesthetic toxicity are the most important steps in managing an overdose. In the event you suspect that a patient is experiencing any of the aforementioned signs or symptoms, the topical anesthetic must be immediately washed off. The patient should be placed in a supine position and vital signs taken. If the patient has lost consciousness, maintenance of a patent airway and ventilation are a top priority. Benzodiazepines may be administered, and serum lidocaine levels should be checked. Anticonvulsants should be provided asprophylaxis or to treat seizures induced from anesthesia toxicity. Topical Anesthetics for Dermatologic Procedures: A Review JOSEPH F. SOBANKO, MD,* CHRISTOPHER J. MILLER, MD,*ANDTINA S. ALSTER, MD
It must be emphasized to the patient that improper product use can result in serious adverse events. The U.S. Food and Drug Administration (FDA) issued a public health advisory in 2007 reporting at least two instances of death when young women applied large volumes of topical anesthesia under occlusion for very extended duration to their legs before laser hair removal. http://www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/DrugSafetyInformationfor HealthcareProfessionals/PublicHealthAdvisories/ucm054718.htm
Despite a large volume of FDA warnings, a large number of pharmaceutically compounded topical anesthetics remain in use for outpatient procedures such as laser hair removal, rejuvenation, resurfacing or other soft tissue augmentation. DA. Warns five firms to stop compounding topical anesthetic creams. Food and Drug Administration: Washington, DC, 2006
Concern grew because of the presence of higher concentrations of the compounded anesthetic mixtures in comparison to FDA-approved and monograph compliant products.
It may be prudent to also be wary of medical device distributors and representatives who supply their own compounded products when demonstrating a device they are trying to sell you. You may not know how or where they procured it nor the safety standards under which it was produced.
In the event a sales representative is attempting to sell you a compounded topical anesthetic, keep in mind there are very high commissions paid on these products and the representative may not be aware (or be concerned) of the rules governing access to topical anesthetics (which happen to be fairly strict in nature). see US FDA rule Compound Quality Act.
There are strict compliance policies, both State and Federal that regulate anticipatory compounding as well as other policies regarding the manufacture, sale and use of compounded anesthetics.
High Risk Topical Anesthetics:
Compounded products, in particular, inappropriately, highly concentrated products, present a potentially higher degree of risk than those approved or monograph complaint anesthetics.
This is primarily due to:
Significant variability in product quality and accurate dosing of these compounded products becomes difficult because they are packaged in widely different containers.
Compounded products have a low therapeutic index and are often improperly labeled. All of these factors increase the risk of adverse events, including
overdose, seizures, arrhythmias, and death and should prompt practitioners to limit the use of topical anesthetics to those approved by the FDA or in compliance with established monograph policies. Kravitz ND. The use of compound topical anesthetics: a review. J Am Dent Assoc 2007;138:1333 – 9
Clinicians are increasingly using topical lidocaine numbing cream products to decrease the pain associated with superficial dermatologic, aesthetic, laser and needle insertion procedures. Lidocaine-containing products play an integral role by providing patient comfort with minimal side effects.
Risk of adverse events can be dramatically decreased when appropriately adhering to basic precautionary methods of application.
Careful selection and application of topical anesthetics can decrease or eliminate pain during many cutaneous procedures, reduce anatomic distortion by minimizing volume of intradermal local anesthesia, and decrease anxiety in patients who fear pain from procedures.
NOTE: This information is provided for entertainment and personal education purposes only and does not circumvent the need to consult with licensed medical or pharmacy professionals prior to using topical anesthetic products. There may be omissions that warrant further investigation. This information should not be relied upon as confirmed professional recommendations for use. The author expressly represents that this information is not to be used as medical or legal advice in any form.