Generic Name

Lidex

Mechanism

Lidex exerts its anesthetic effect by binding to the *sodium‑channel* channel in the neuronal membrane.
• → Inhibits the influx of Na⁺ ions → Renders the nerve membrane impermeable to depolarizing stimuli.
• ↓ Reduces action‑potential propagation → Produces reversible local anesthesia.
• The drug’s effect is concentration‑dependent and is potentiated by *epinephrine* (when added), which causes vasoconstriction and prolongs onset.

Pharmacokinetics

• Absorption: Rapid intravascular uptake when injected in vascularized tissues; slower in subcutaneous or intramuscular sites.
• Distribution: Lipophilic; distributes widely throughout the body, with a volume of distribution of ~3.5 L/kg.
• Metabolism: Hepatic cytochrome P450 (primarily *CYP1A2*); minor contribution by *glucuronidation*.
• Excretion: Renal (≈90 %); unmetabolized via biliary route.
• Half‑life: 1.5–4 h (varies with route and presence of epinephrine).
• Peak plasma concentrations usually 5–20 min post‑injection.

Indications

• Dental anesthesia (e.g., infiltration of maxillary and mandibular tissues, nerve blocks).
• Minor surgical procedures (skin, mucous‑membrane, and superficial muscle anesthesia).
• Ophthalmic procedures (conjunctival and corneal topical anesthesia).
• Prosthetic device placement (e.g., prosthetic valves, intra‑articular injections).

Contraindications

• Absolute Contraindications:
• Known hypersensitivity to lidocaine or any local anesthetic.
• Severe systemic hypoxia oric shock (due to risk of systemic toxicity).
• Relative Contraindications / Precautions:
• Cardiac conduction disorders (AV block, prolonged QTc).
• Severe hepatic or renal impairment (may prolong systemic exposure).
• Respiratory insufficiency / COPD (risk of central apnea).
• Pregnancy – category IB; use only if clearly indicated.
• Concurrent CNS‑active drug use (benzodiazepines, barbiturates) – enhances CNS toxicity.

Dosing

• *Add 0.01 % epinephrine* to 1 % Lidex for prolonged duration (≥1.5 h) and reduced systemic absorption.
• Maximum daily dose (adult) ≈ 400 mg (approximately 0.5–0.6 % of body weight).
• Sublingual route not recommended due to unpredictable absorption.

Adverse Effects

Monitoring

• Vital signs (BP, HR, O₂ saturation) pre‑ and post‑administration.
• ECG in patients with existing conduction abnormalities or when high systemic doses are anticipated.
• Symptoms of CNS toxicity: monitor for tinnitus, circumoral numbness, seizures.
• Observation period: 30–60 min after injection for systemic toxicity, especially after epinephrine‑augmented doses.
• Serum lidocaine levels only in cases of suspected systemic toxicity.

Clinical Pearls

1. Aspiration is a must. The classic evidence that a needle tip is intravascular prevents early systemic toxicity.
2. Epinephrine improves both safety and efficacy: lowers peak systemic concentrations and prolongs anesthesia, but beware of tachycardia and hypertension.
3. Buffer the solution (adjust pH to 7.4–7.8) to reduce injection pain, especially in dental procedures where patient discomfort is a major concern.
4. Use “cold” 1 % solutions for sedation‑intolerant patients; keep the syringe at 4 °C to lessen post‑injection numbness.
5. If patient shows early CNS toxicity, stop the injection, give 100 % oxygen, and administer IV lipid emulsion (1 mL/kg over 5 min, repeat if needed).
6. Do not exceed 400 mg in a single session unless the patient is monitored with ECG and vital signs.
7. Bittering agent for topical ophthalmic: adding 0.01 % benzocaine to the solution can mask the bitter taste of lidocaine, improving patient tolerance.

Key Takeaway:
Lidex’s effectiveness hinges on precise dosing, aspiration, and vigilant monitoring for systemic toxicity, particularly when epinephrine is added. Its widespread use across dentistry, minor surgery, and ophthalmology makes it a cornerstone of local anesthesia practice—provided that safety guidelines are consistently followed.