finds widespread usage in dermatology, cosmetic surgical, and medicinal uses to prevent discomfort and pain. It finds usage on regular basis pre-laser surgery, microneedling, tattooing, waxing, and minimal surgery. Lidocaine is nontoxic but is toxic, hypersensitivity reaction, or failure with the abuse it can be caused with. Among side effects reported after the use of local anesthetics, about 14% were due to overdose, abuse with extended duration of use or extensive area of application to the skin, based on data up to 2023 compiled by the American Academy of Dermatology (AAD). Safety and efficacy at the administration site are covered here, highlighting mode of application, dose control, contraindication, latency period, hypersensitivity test, and emergency procedure.
Application Steps
There should be good application of lidocaine numbing cream to ensure complete absorption and analgesia. Begin by washing the skin with warm water and mild soap and then dry. Grease and dirt may jeopardize absorption up to 30%, one that a study recently published by a 2021 Journal of Clinical Anesthesia had determined. Wear protective gloves against accidental absorption since already in a study conducted by the 2022 European Society of Anesthesia it had already been established that 5% of accidental lidocaine toxicity were via hands of healthcare workers.
It is to be applied thin even layers and pea-sized quantity of skin to a surface area of 5 cm². Frictioning twice doubles the quantity of absorption by 20-35%, the highest in susceptibility to side effects. Plastic wrap or occlusive dressing over the skin increases absorption by 50-70% according to a 2022 Harvard Medical School report but with toxic hazards the longer it is worn. Permitting the cream to enter fully upon usage and wiping out the leftovers afterwards is the most secure practice.
Dose Control
Excess of lidocaine anesthetic cream causes systemic toxicity in the form of dizziness, arrhythmia, seizure, or death in severe cases. Single-dose application of a maximum of 5g of 5% lidocaine cream on a maximum skin surface area of 600 cm² is advised by FDA 2023. Duration of application should not be more than 60 minutes because longer duration of application enhances absorption into the blood, the risk of which is lidocaine-induced methemoglobinemia, a condition where oxygen supply is impaired.
One of the Mayo Clinic’s 2021 case reports was that a 35-year-old female patient applied 10g of lidocaine cream to an extensive area before laser hair removal. She became confused, had blurred vision, and palpitations and was discovered to have lidocaine toxicity. That implies one needs to take dosage along with not redosing too frequently since redosing lidocaine within 30 minutes has been found in research to double the absorption systemically.
Contraindicated Groups
Certain groups do not use or use lidocaine numbing cream with caution. Pregnant and breastfeeding women must consult a doctor prior to use, as in a 2022 National Institute of Health (NIH) study there was a 12% increase in fetal bradycardia with the excessive pregnancy use of lidocaine. Infants under the age of 12 months have 25-30% reduced metabolism of lidocaine, increased toxicity levels, as confirmed in a 2023 Pediatrics Journal study.
Liver and kidney disease patients must exercise extreme care in using lidocaine because lidocaine is metabolized by the liver and excreted by kidneys. The New England Journal of Medicine (2022) concluded that toxic levels are achieved earlier in hepatic or renal insufficiency patients. Cardiac disease patients, particularly arrhythmias, must be very careful because lidocaine has sodium channel activity and can induce arrhythmias. A 2023 American Heart Association report also found that excessive absorption can lead to underlying cardiac conduction disease. Patch testing must be done in local anesthetic allergic reaction history patients prior to their administration of full doses. Journal of Allergy and Clinical Immunology’s 2022 review article needed around 2.3% of the patients to show hypersensitivity reactions against local anesthetics.
Onset Time
Onset and duration of lidocaine numbing cream are concentration-, route of administration-, and intersubject variability-dependent. Onset of 4% lidocaine cream is 25-30 minutes and duration is 60-90 minutes, and onset of 5% lidocaine cream is 15-20 minutes and duration is 90-120 minutes, according to 2023 clinical pharmacology studies.
Application with occlusive dressing is 30% shorter in onset time but also increases the systemic absorption to the same degree, as researched in 2023 by Johns Hopkins University. If used during invasive numbing procedures like microneedling or tattooing, wait at least 45 minutes post-application time for optimal effect.
Allergy Test
In case of prevention from allergy, a patch test should be conducted 24 hours prior to final application. According to American College of Allergy, Asthma, and Immunology (2023), a pea-sized patch over 1 cm² on the inside of the forearm is recommended. Final application is usually safe if there is no redness, swelling, itchiness, or blistering in 24 hours.
Dermatology update 2023 detected 5-7% of new users with minor inflammation and 0.5-1% needing medical attention for a severe allergy. Allergic individuals who have an allergy to an anesthetic or preservative found in numbing creams should get in touch with a dermatologist prior to use.
Emergency Response
Overdose or hypersensitivity reaction on repeated treatment is a necessity for Lidocaine. Dizziness, somnolence, facial anesthesia, or nausea is a presenting feature in the case of overdose. In case of such, when overdosage is performed, the cream should be promptly removed and the patient resuscitated.
Toxicity symptoms of abnormal heart rhythm, confusion, tremor, or convulsion, severe and moderate, should be reported to a doctor at once. According to 2023 emergency medical practice, emergency is to be called and rolled onto position the person onto his or her side. Oxygen is to be given if the person can handle it.
Signs of anaphylactic reaction like swelling, shortness of breath, and low blood pressure justify the immediate use of an epinephrine auto-injector (EpiPen)