Usage
Lidocaine + Tetracaine cream is a topical anesthetic indicated for use on intact skin in adults to provide local analgesia for superficial dermatological procedures. These procedures include dermal filler injections, pulsed dye laser therapy, facial laser resurfacing, and laser-assisted tattoo removal. It falls under the pharmacological classification of local anesthetics, specifically a combination of an amide local anesthetic (lidocaine) and an ester local anesthetic (tetracaine). The mechanism of action involves blocking sodium channels in nerve fibers, thereby inhibiting nerve impulse initiation and conduction, leading to a localized loss of sensation.
Alternate Names
While “Lidocaine + Tetracaine” is the generic name, the combination is marketed under various brand names, most notably Pliaglis and Synera. There might be other international or regional brand name variations as well.
How It Works
Pharmacodynamics: Lidocaine + Tetracaine exerts its anesthetic effect by reversibly binding to sodium channels within neuronal cell membranes. This binding action prevents the influx of sodium ions, which are essential for depolarization and subsequent propagation of nerve impulses. The combined action of both anesthetics results in enhanced and prolonged local anesthesia.
Pharmacokinetics: After topical application to intact skin, both lidocaine and tetracaine are absorbed into the systemic circulation. However, the extent of absorption is limited, minimizing systemic side effects. Lidocaine is metabolized primarily in the liver by CYP enzymes, while tetracaine is rapidly hydrolyzed by plasma cholinesterases. Both drugs and their metabolites are primarily excreted via the kidneys.
Mode of Action: The combination acts locally on sensory nerve endings in the skin. It blocks sodium channels, preventing the transmission of pain signals to the brain. The eutectic mixture of lidocaine and tetracaine in the cream formulation ensures that both drugs are in a liquid oil state at room temperature, allowing for better skin penetration.
Elimination Pathways: Lidocaine is metabolized primarily in the liver and excreted by the kidneys. Tetracaine is rapidly hydrolyzed in plasma, with the resulting metabolites excreted renally.
Dosage
Standard Dosage
Adults: A thick layer of cream is applied to intact skin 20-30 minutes before procedures like dermal filler injections, pulsed dye laser therapy, or facial resurfacing, and 60 minutes before laser-assisted tattoo removal. The amount to apply is based on the surface area being treated.
Children: Lidocaine + Tetracaine is not indicated for use in pediatric patients less than 18 years of age.
Special Cases:
- Elderly Patients: Elderly patients may be more sensitive to the systemic effects, but dosage adjustments are not typically required. Monitor closely.
- Patients with Renal Impairment: Dosage adjustments may be necessary. Monitor closely for systemic toxicity.
- Patients with Hepatic Dysfunction: Patients with severe hepatic disease are at greater risk of developing toxic plasma concentrations due to impaired metabolism. Exercise caution and consider dosage adjustment.
- Patients with Comorbid Conditions: Use with caution in patients with certain medical conditions, such as severe cardiovascular disease, as they may be more susceptible to adverse effects.
Clinical Use Cases: Lidocaine + Tetracaine is primarily intended for superficial dermatological procedures as mentioned above. Its use for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations is generally not recommended as other, more potent anesthetic agents are typically employed in those settings.
Side Effects
Common Side Effects: Localized skin reactions (erythema, edema, pruritus, blanching, and/or discoloration at the application site).
Rare but Serious Side Effects: Methemoglobinemia (characterized by cyanosis, headache, tachycardia, dyspnea, lightheadedness, and/or fatigue), allergic reactions (including urticaria, angioedema, bronchospasm, and/or shock), and systemic toxicity (CNS excitation or depression manifesting as dizziness, lightheadedness, seizures, respiratory depression, and/or cardiac arrest).
Long-Term Effects: Long-term effects of topical Lidocaine + Tetracaine use are unlikely due to its localized action and limited systemic absorption when used as directed.
Adverse Drug Reactions (ADR): Clinically significant ADRs include methemoglobinemia and allergic reactions, requiring prompt intervention.
Contraindications
- Known hypersensitivity to lidocaine, tetracaine, local anesthetics of the amide or ester type, or para-aminobenzoic acid (PABA).
- Application to broken or irritated skin, mucous membranes, or near the eyes.
Drug Interactions
- Other local anesthetics (additive systemic effects).
- Class I antiarrhythmics (additive cardiac depressant effects).
- Medications that can induce methemoglobinemia (e.g., sulfonamides, nitrates).
Pregnancy and Breastfeeding
- Pregnancy: Lidocaine + Tetracaine is categorized as Pregnancy Category B. While animal studies have not shown fetal harm, adequate and well-controlled studies in pregnant women are lacking. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.
- Breastfeeding: Lidocaine is excreted in breast milk; the extent of tetracaine excretion is unknown. Exercise caution when administering to breastfeeding women. Avoid applying the cream directly to the nipple or areola.
Drug Profile Summary
- Mechanism of Action: Sodium channel blocker, inhibiting nerve impulse initiation and conduction.
- Side Effects: Localized skin reactions, methemoglobinemia, allergic reactions, systemic toxicity.
- Contraindications: Hypersensitivity to ingredients, broken skin, mucous membranes.
- Drug Interactions: Other local anesthetics, Class I antiarrhythmics, medications inducing methemoglobinemia.
- Pregnancy & Breastfeeding: Category B; caution advised during breastfeeding.
- Dosage: Apply a thick layer to intact skin 20-60 minutes before the procedure, depending on the procedure.
- Monitoring Parameters: Observe for signs of methemoglobinemia and allergic reactions.
Precautions
- Ensure skin integrity before application.
- Avoid contact with eyes and mucous membranes.
- Monitor for signs of local and systemic adverse effects.
- Use caution in patients with hepatic disease, cardiovascular disease, or other relevant comorbidities.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Lidocaine + Tetracaine?
A: Apply a thick layer to intact skin 20-30 minutes before procedures such as dermal fillers and 60 minutes before laser tattoo removal. The amount depends on the treatment area. Not for use in children under 18.
Q2: What are the common side effects?
A: Common side effects include redness, swelling, blanching, and/or discoloration at the application site.
Q3: Can Lidocaine + Tetracaine be used on broken skin?
A: No, it should only be applied to intact skin. Application to broken skin can lead to increased systemic absorption and potential toxicity.
Q4: Is Lidocaine + Tetracaine safe during pregnancy?
A: It is Pregnancy Category B. Use only if the benefit outweighs the risk. Consult with an obstetrician.
Q5: Can I breastfeed while using this cream?
A: Use with caution while breastfeeding. Avoid applying to the nipple area.
Q6: What should I do if I experience a burning sensation during application?
A: Remove the cream immediately and cleanse the area.
Q7: What are the signs of methemoglobinemia?
A: Pale, gray, or blue skin, headache, rapid heart rate, shortness of breath, lightheadedness, and fatigue. Seek immediate medical attention if these occur.
Q8: Can Lidocaine + Tetracaine be used for deep tissue procedures?
A: No, it’s intended only for superficial dermatological procedures. For deeper procedures, other anesthetic techniques are typically employed.
Q9: How does Lidocaine + Tetracaine differ from other local anesthetics?
A: It combines an amide and ester anesthetic for a potentially longer duration and better skin penetration, but should not be used in patients with hypersensitivity to amide or ester anesthetics.
Q10: Can this cream be used on the face?
A: Yes, it can be used on intact facial skin for approved procedures. However, exercise caution around the eyes and mucous membranes.
