LIDODERM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LIDODERM (LIDODERM).
Lidocaine is an amide-type local anesthetic that blocks voltage-gated sodium channels (Nav1.7) in nerve cell membranes, inhibiting depolarization and conduction of nerve impulses, thereby producing both local anesthesia and systemic analgesia.
| Metabolism | Primarily hepatic metabolism via cytochrome P450 isoenzymes, mainly CYP1A2 and CYP3A4, to active metabolites (MEGX and GX) with minor renal excretion. |
| Excretion | Renal excretion of metabolites (primarily 4-hydroxy-2,6-xylidine glucuronide) accounts for >85% of elimination; <3% excreted unchanged; biliary/fecal elimination minimal (<10%). |
| Half-life | Terminal elimination half-life is 3–5 hours after topical application; after intravenous administration, half-life is 1.5–2 hours. Clinical context: Systemic accumulation possible with prolonged use on inflamed skin. |
| Protein binding | 70–80% bound to plasma proteins, primarily alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | 0.6–1.0 L/kg (intravenous); large Vd indicates extensive tissue distribution, including highly perfused organs and adipose tissue. |
| Bioavailability | Topical: 3% ± 1% from intact skin; increased to 10–30% on inflamed or abraded skin. |
| Onset of Action | Topical: 2–5 minutes for analgesic effect on intact skin; complete effect within 30 minutes. |
| Duration of Action | Topical: Analgesic effect lasts 4–12 hours after patch removal (dose-dependent). Clinical notes: Duration depends on patch retention and blood flow; reapplication every 12 hours recommended. |
Apply 1 to 3 patches (5% lidocaine) to intact skin over most painful area for up to 12 hours within a 24-hour period; maximum 3 patches at once.
| Dosage form | PATCH |
| Renal impairment | No dosage adjustment required for GFR >= 30 mL/min; use with caution and monitor for toxicity if GFR < 30 mL/min due to risk of lidocaine accumulation; no specific dose recommendations available. |
| Liver impairment | Contraindicated in Child-Pugh Class C; for Child-Pugh A and B, use with caution with maximum 1 patch at a time and reduced application area; consider reducing application time if signs of toxicity appear. |
| Pediatric use | Not recommended for children under 18 years; safety and efficacy not established. For patients 18 years and older, use adult dosing. |
| Geriatric use | Use with caution; start with 1 patch and monitor for local adverse effects; may require fewer patches due to thinner skin and increased absorption; maximum 3 patches per day for 12 hours on, 12 hours off. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for LIDODERM (LIDODERM).
| Breastfeeding | Lidocaine is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.4. The relative infant dose is estimated to be 0.5-1% of the maternal weight-adjusted dose. At therapeutic doses, it is generally considered compatible with breastfeeding. However, monitor the infant for signs of local anesthetic toxicity (e.g., drowsiness, irritability) if the mother uses high doses or multiple applications. |
| Teratogenic Risk | Lidocaine is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. However, lidocaine can cross the placenta and may cause fetal bradycardia or central nervous system depression when used in high doses or during paracervical block. Use during the first trimester is not associated with major malformations; risks during second and third trimesters are considered low with appropriate dosing. Avoid use near delivery if alternative agents are available due to potential neonatal effects. |
■ FDA Black Box Warning
Lidoderm is not FDA approved with a black box warning. However, inappropriate use (e.g., applying to broken skin, using excessive patches) can lead to systemic lidocaine toxicity, which may be life-threatening.
| Serious Effects |
["Hypersensitivity to lidocaine or any amide-type local anesthetics","History of sensitivity to lidocaine patch components"]
| Precautions | ["Do not use on broken or inflamed skin; increased risk of systemic absorption and toxicity.","Monitor for signs of lidocaine toxicity (e.g., perioral numbness, tinnitus, seizures, cardiac arrhythmias), especially if multiple patches are applied.","Use with caution in patients with severe hepatic impairment, as metabolism may be reduced.","Avoid concomitant use with Class I antiarrhythmic drugs (e.g., tocainide, mexiletine) due to additive toxicity."] |
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| Fetal Monitoring | Monitor for maternal local anesthetic toxicity: perioral numbness, metallic taste, tinnitus, seizures, arrhythmias. Monitor fetal heart rate if lidocaine is used during labor (e.g., for epidural or pudendal block) as it may cause fetal bradycardia. In neonates, observe for CNS depression if lidocaine was used within 2 hours of delivery. |
| Fertility Effects | Lidocaine has no known adverse effects on fertility in animal studies or human reports. Topical or local administration at therapeutic doses is not expected to impair reproductive function. |