What is the recommended concentration of lidocaine for intramuscular (IM) injection?

From the Guidelines

For intramuscular (IM) administration of lidocaine, the recommended concentration is typically 1% (10 mg/mL). This concentration is commonly used for most adult IM applications, with typical volumes ranging from 1-5 mL per injection site depending on the specific indication 1. The maximum safe dose is 4.5 mg/kg without epinephrine or 7 mg/kg with epinephrine, as suggested by guidelines for the use of local anesthesia in office-based dermatologic surgery 1.

Key Considerations

• The maximum safe dose of local infiltrated anesthesia is unknown, but guidelines recommend no more than 4.5 mg/kg of lidocaine and 7.0 mg/kg of lidocaine with epinephrine for adults 1.
• For children, no more than 1.5-2.0 mg/kg of lidocaine and 3.0-4.5 mg/kg of lidocaine with epinephrine should be administered in a single treatment 1.
• When administering lidocaine IM, it's essential to aspirate before injection to avoid intravascular administration, inject slowly, and monitor for signs of systemic toxicity such as perioral numbness, metallic taste, dizziness, or cardiac arrhythmias.

Administration and Monitoring

• Lidocaine works by blocking sodium channels in nerve cell membranes, preventing the initiation and conduction of nerve impulses.
• The onset of action for IM lidocaine is typically 5-15 minutes with a duration of 1-2 hours, though this varies based on the specific formulation and individual patient factors.
• It is crucial to follow the recommended guidelines and take necessary precautions to minimize the risk of adverse effects and ensure safe administration of lidocaine for IM use 1.

From the FDA Drug Label

The above suggested concentrations and volumes serve only as a guide. In some cases it will be necessary to dilute available concentrations with 0.9 % sodium chloride injection in order to obtain the required final concentration.

The concentration of lidocaine for IM is not explicitly stated in the provided drug label. However, it can be inferred that the concentration should be determined based on the patient's age, weight, and the specific procedure being performed, with the goal of using the lowest effective concentration and lowest effective dose to guard against systemic toxicity.

• The label suggests that available concentrations may need to be diluted with 0.9% sodium chloride injection to obtain the required final concentration.
• The maximum recommended dose is 4.5 mg/kg (2 mg/lb) of body weight, and in general, it is recommended that the maximum total dose does not exceed 300 mg 2.

From the Research

Concentration of Lidocaine for IM

• The concentration of lidocaine for intramuscular (IM) administration is not explicitly stated in terms of a specific concentration (e.g., percentage or milligrams per milliliter) in the provided studies, but rather as a dose per kilogram of body weight.
• In the study 3, patients received lidocaine 1.5 mg · kg(-1) administered into the deltoid muscle.
• Another study 4 administered lidocaine (100 mg ml(-1)) at a dose of 2 mg kg(-1) intramuscularly.
• A study on the effects of lidocaine as a diluent for ceftriaxone 5 used 1% lidocaine, but this concentration is in the context of being a diluent, not the primary IM administration of lidocaine itself.
• It's crucial to note that the appropriate concentration and dosage of lidocaine for IM use should be determined based on the specific clinical context and guidelines, considering factors such as the patient's weight, the procedure being performed, and potential interactions with other medications.

Dosage Considerations

• The dosage of lidocaine for IM administration, as mentioned, is often given in milligrams per kilogram of body weight, highlighting the importance of patient-specific dosing.
• Studies 3 and 4 demonstrate the efficacy of lidocaine in reducing the required doses of propofol for anesthesia induction and maintenance when administered intramuscularly, but they do not provide a universal concentration that can be applied across all scenarios.
• The use of lidocaine in conjunction with other procedures or medications, such as its application in laser-assisted delivery for topical anesthesia 6, further underscores the need for careful consideration of the appropriate dosage and concentration based on the specific application and clinical setting.