LIDOCAINE HYDROCHLORIDE PRESERVATIVE FREE
Clinical safety rating: safe
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
Lidocaine is a local anesthetic that stabilizes the neuronal membrane by inhibiting sodium ion channels, thereby blocking the initiation and conduction of nerve impulses. It also exhibits cardiac effects as a class IB antiarrhythmic agent by modulating sodium channels in myocardial cells.
| Metabolism | Lidocaine undergoes extensive hepatic metabolism primarily via cytochrome P450 (CYP1A2 and CYP3A4) to active metabolites (monoethylglycinexylidide and glycinexylidide) that may contribute to efficacy or toxicity. |
| Excretion | Renal: ~90% as metabolites (primarily monoethylglycinexylidide [MEGX] and glycinexylidide [GX]), <10% unchanged. Fecal: <1%. |
| Half-life | 1.5–2 hours (terminal) in healthy adults; prolonged in hepatic impairment (up to 5–7 hours), heart failure (up to 10 hours), or with continuous infusion (>24 h) due to accumulation. Context: requires monitoring in hepatic or cardiac dysfunction to avoid toxicity. |
| Protein binding | 60–80% bound, primarily to alpha-1-acid glycoprotein (AAG); binding decreases in conditions with low AAG (e.g., pregnancy, neonates). |
| Volume of Distribution | 1.1–1.6 L/kg (central Vd: ~0.5 L/kg; steady-state Vd: ~1.3 L/kg). Indicates extensive tissue distribution, with rapid uptake into well-perfused organs (brain, heart). |
| Bioavailability | IM: 100% (absolute); Oral: <40% (extensive first-pass metabolism); Topical (intact skin): <20% (variable); Nebulized: ~70% (via metered-dose inhaler). |
| Onset of Action | IV: 45–90 seconds; IM: 5–15 minutes; Subcutaneous infiltration: immediate (within seconds); Topical (e.g., mucosal): 2–5 minutes; Nebulized: 5–10 minutes. |
| Duration of Action | IV bolus: 10–20 minutes (rapid redistribution); Continuous IV infusion: variable, titrated to effect; IM: 60–90 minutes; Subcutaneous infiltration: 30–60 minutes (with epinephrine: 2–6 hours); Topical: 15–30 minutes (mucosa). |
| Molecular Weight | 234.34 |
1-4 mg/kg via intravenous bolus, not to exceed 300 mg; may be followed by continuous infusion of 1-4 mg/min.
| Dosage form | INJECTABLE |
| Renal impairment | No adjustment required for GFR > 30 mL/min; use with caution and reduce dose in severe renal impairment (GFR < 30 mL/min) due to risk of metabolite accumulation. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25-50%; Child-Pugh C: reduce dose by 50% or avoid use. |
| Pediatric use | Neonates and infants: 1-1.5 mg/kg IV bolus; children: 1-1.5 mg/kg IV bolus, may repeat every 5-10 minutes up to 5 mg/kg total; continuous infusion: 20-50 mcg/kg/min. |
| Geriatric use | Reduce initial dose by 50% in elderly patients (age >70) and adjust based on response and liver function. |
| 1st trimester | Lidocaine is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but adequate human studies in first trimester are lacking. Use only if clearly needed. |
| 2nd trimester | No evidence of teratogenicity in second trimester; considered safe for local anesthesia when indicated. Avoid excessive doses to prevent maternal toxicity. |
| 3rd trimester | Use during third trimester may be associated with neonatal CNS depression if administered near term. Avoid paracervical block in obstetrics due to risk of fetal bradycardia. |
Clinical note
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
| FDA category | Animal |
| Placental transfer | Lidocaine readily crosses the placenta via passive diffusion. Fetal/maternal concentration ratio ranges 0.5-0.7. Protein binding is lower in fetus, leading to higher free drug levels. Prolonged use or high doses may cause fetal CNS depression. |
■ FDA Black Box Warning
Lidocaine hydrochloride preservative-free preparations for spinal anesthesia should be used with caution as it may cause severe neurologic effects such as cauda equina syndrome, permanent paralysis, and sensory deficits. The lowest effective dose should be administered.
| Common Effects | ventricular arrhythmias |
| Serious Effects |
Hypersensitivity to lidocaine or amide-type anestheticsSevere heart block (second- or third-degree) without pacemakerUncontrolled seizure disordersMyasthenia gravis (caution, but absolute contraindication for certain formulations)Hypovolemia or severe hypotension (relative, but absolute for large doses)
| Precautions | Risk of systemic toxicity (CNS and cardiovascular) due to accidental intravascular injection or overdosage, Use with caution in patients with hepatic impairment, severe renal disease, hypovolemia, or heart block (except in emergent situations for arrhythmias), May cause methemoglobinemia, especially in neonates or with co-administration of oxidizing agents, Avoid injection into infected or inflamed tissues as absorption may be altered, Monitor for signs of CNS toxicity (dizziness, perioral numbness, seizures) or cardiovascular depression |
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| Breastfeeding | Lidocaine is excreted into breast milk in small amounts (milk-to-plasma ratio ~0.4). After a single dose, the estimated infant dose is 0.4-1.2% of the maternal weight-adjusted dose, which is below levels of concern. However, repeated or high-dose administration may lead to accumulation. Observe infant for signs of CNS depression or arrhythmias. |
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Lidocaine hydrochloride is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. However, lidocaine crosses the placenta and may cause fetal bradycardia and central nervous system depression if used in high doses or during paracervical block. In the first trimester, no increased risk of major malformations has been reported. During the second and third trimesters, use is considered safe for local anesthesia, but caution is advised for high doses and continuous infusions which may lead to fetal acidosis and neurobehavioral depression. Use during labor and delivery may cause neonatal depression if excessive maternal doses are administered. |
| Fetal Monitoring | Maternal monitoring includes heart rate, blood pressure, respiratory rate, and level of consciousness, especially with high doses or continuous infusions. Fetal monitoring should include heart rate monitoring during labor, particularly if paracervical block is used, to detect bradycardia. Neonatal monitoring post-delivery is recommended for signs of lidocaine toxicity if high maternal doses were administered. Electrocardiographic (ECG) monitoring may be considered in high-dose or prolonged infusions to assess for cardiac conduction abnormalities. |
| Fertility Effects | In animal studies, lidocaine did not demonstrate adverse effects on fertility at clinically relevant doses. In humans, no specific data are available regarding the effect of lidocaine on fertility. However, given its short-term use and local administration, significant reproductive impact is unlikely. There is no evidence of impairment of male or female fertility from standard therapeutic use. |
| Food/Dietary | No known food interactions. Avoid alcohol consumption 24 hours before and after procedure as it may increase risk of side effects. |
| Clinical Pearls | Preservative-free formulation is mandatory for epidural, spinal, or intravenous use to avoid neurotoxicity. Maximum single dose without epinephrine is 4.5 mg/kg (300 mg); with epinephrine 7 mg/kg (500 mg). Always aspirate before injection to prevent intravascular administration. Can cause methemoglobinemia in neonates; use with caution in patients with G6PD deficiency. Onset of action for infiltration is 2-5 minutes, duration 30-60 minutes without epinephrine. |
| Patient Advice | Report any numbness of lips, tongue, metallic taste, or ringing in ears immediately. · Avoid driving or operating machinery until effects of anesthesia have fully worn off. · Do not eat or drink until normal sensation returns to prevent accidental biting or choking. · Inform your doctor if you have liver disease, heart problems, or are pregnant/breastfeeding. · This medication may cause temporary weakness or loss of sensation in the injection area. |