Lidocaine 23% | Tetracaine 7%

Route: Topical application to intact skin. Apply a thick layer (typically 1–2.5 grams per 10 cm² as directed) to the targeted area under occlusion (plastic wrap or occlusive dressing) for the prescriber-specified duration (typically 20–60 minutes prior to procedure). Remove and wipe off completely before beginning the procedure. Do not apply to mucous membranes, broken skin, or large body surface areas. Prescriber must specify the total amount, surface area, and occlusion time.

Dosing is entirely prescriber-determined. Key parameters:

• Application amount per unit area, total surface area treated, and occlusion time must all be specified by the prescriber to avoid systemic local anesthetic toxicity.
• Maximum safe dose thresholds are weight-dependent; extreme caution is required with large surface areas (particularly in children), broken skin, or prolonged occlusion, all of which increase systemic absorption dramatically.
• Duration of anesthesia typically begins 20–30 minutes after application and may last 1–2 hours post-removal depending on tissue characteristics.

• Lidocaine 23%: Diffuses across the neuronal membrane into the axoplasm in its uncharged (lipophilic) form. Inside the neuron, lidocaine equilibrates to its charged (cationic) form, which blocks the inner pore of voltage-gated Na⁺ channels (Nav1.1, Nav1.5, Nav1.7, Nav1.8) in a use-dependent manner. This prevents action potential propagation in Aδ and C sensory nerve fibers, producing anesthesia. Lidocaine's amide bond resists enzymatic hydrolysis, and it is metabolized by hepatic CYP3A4 and CYP1A2.
• Tetracaine 7%: An ester-type anesthetic that diffuses into neurons and blocks the inner Na⁺ channel pore through the same membrane-stabilizing mechanism as lidocaine. Tetracaine is more lipophilic, which increases skin penetration and extends duration of action. As an ester, it is hydrolyzed by plasma pseudocholinesterase (butyrylcholinesterase) and tissue esterases, yielding para-aminobenzoic acid (PABA) — a potential allergen. The two anesthetic classes act synergistically on Na⁺ channels: lidocaine provides rapid onset, tetracaine provides sustained, deep anesthesia.

This high-concentration formulation (lidocaine 23% + tetracaine 7%) is intended for prescriber-directed pre-procedure topical anesthesia in dermatologic and aesthetic medicine settings where commercial lower-concentration products (e.g., EMLA 2.5% lidocaine/2.5% prilocaine) are insufficient. Clinical applications include: laser resurfacing and ablative procedures, microneedling, chemical peels, filler injection, tattoo procedures, and minor surgical excisions.

Monitoring and Safety Considerations: The high concentration necessitates strict prescriber oversight of application area size and occlusion time. Risk of systemic local anesthetic toxicity (LAST) increases substantially with: broken skin, large surface area, prolonged occlusion, mucosal application, or high-vascularity areas. Signs of LAST include perioral numbness, tinnitus, dizziness, seizures, and cardiac arrhythmia — treat as a medical emergency. Prescribers should document weight-based maximum safe dosing calculations.

Contraindications:

• Known hypersensitivity to amide-type local anesthetics (lidocaine) or ester-type local anesthetics (tetracaine).
• Known hypersensitivity to PABA or PABA-containing compounds (tetracaine metabolite).
• Application to mucous membranes, open wounds, or highly vascularized tissue (dramatically increases systemic absorption).
• Congenital or acquired methemoglobinemia (use in patients with glucose-6-phosphate dehydrogenase deficiency or concurrent methemoglobin-forming agents — more relevant with prilocaine, but monitor).

Warnings & Precautions:

• Systemic local anesthetic toxicity (LAST): The single most important risk. At 23% lidocaine + 7% tetracaine, application to large surface areas (>600 cm²), broken skin, mucous membranes, or under occlusion for extended periods can produce plasma lidocaine concentrations sufficient to cause CNS toxicity (seizures, coma) and cardiovascular toxicity (ventricular arrhythmia, cardiac arrest). Emergency resuscitation equipment and lipid emulsion (Intralipid 20%) must be immediately available when used in clinical settings.
• Plasma cholinesterase deficiency: impaired tetracaine metabolism; use with extreme caution or avoid.
• Hepatic impairment: reduced lidocaine metabolism; lower dose limits apply.
• Pediatric patients: children have greater body surface area to weight ratio and lower plasma protein binding, substantially increasing LAST risk per gram applied.

Drug Interactions:

• CYP3A4 inhibitors (azole antifungals, macrolide antibiotics, grapefruit juice): increase lidocaine plasma levels.
• Class I antiarrhythmics (mexiletine, tocainide): additive cardiac conduction depression.
• Cimetidine: inhibits lidocaine hepatic clearance.
• Succinylcholine: tetracaine may competitively inhibit plasma cholinesterase, prolonging succinylcholine neuromuscular blockade.

Common Side Effects: Local skin reactions (erythema, blanching, edema, pallor at application site); systemic: at excessive doses — perioral numbness, metallic taste, tinnitus, lightheadedness, tachycardia, seizures (LAST). Rare: allergic contact dermatitis (tetracaine/PABA); methemoglobinemia (rare with lidocaine, more relevant with prilocaine).

Store at room temperature (15°C–25°C), away from heat and light. Do not freeze. Keep tightly sealed to prevent evaporation of the cream base. High-concentration local anesthetic preparations should be stored out of reach of children and non-patients. Use within the beyond-use date specified by Genesis Compounding. Discard any unused portion after the procedure session per prescriber instructions.

Why is this such a high concentration of anesthetic?

Many dermatologic and aesthetic procedures require anesthesia deeper in the dermis than commercial lower-concentration products can reliably achieve. The 23% lidocaine and 7% tetracaine concentrations are prescriber-directed to provide the depth of anesthesia required for specific procedures (laser resurfacing, microneedling, tattoo removal). The prescriber determines safe application parameters.

How long does anesthesia last?

Onset of anesthesia typically occurs 20–30 minutes after application under occlusion. Duration of skin anesthesia after removal of the preparation is typically 1–2 hours, depending on skin thickness, vascularity, and individual patient factors.

What is systemic local anesthetic toxicity (LAST) and how is it prevented?

LAST occurs when plasma lidocaine or tetracaine concentrations reach toxic levels, affecting the central nervous system (seizures, coma) and cardiovascular system (arrhythmia, cardiac arrest). Prevention depends strictly on limiting the total amount applied, surface area treated, and occlusion time — all of which are prescriber-specified. Apply only to intact skin.

Is this FDA-approved?

No. This is a patient-specific, prescriber-directed 503A compounded preparation from Genesis Compounding, not FDA-approved as a compounded drug. Commercially, a lidocaine 7%/tetracaine 7% formulation (Pliaglis) exists; this compounded formulation differs in lidocaine concentration.

Can this be used on the face?

Yes, when prescribed for facial procedures, but only on intact skin with strict application parameters (surface area, quantity, and occlusion time) specified by the prescriber. Avoid application near the eyes, nostrils, lips, or mucous membranes.