Usage
Prilocaine is prescribed for local anesthesia. It is classified as a local anesthetic, specifically an amide-type local anesthetic. Prilocaine’s mechanism of action involves blocking sodium channels in nerve fibers. This action prevents the initiation and conduction of nerve impulses, thus producing the anesthetic effect.
Alternate Names
Prilocaine hydrochloride is sometimes used. Brand names include Citanest and Citanest Plain Dental. A topical combination of lidocaine and prilocaine is marketed under the brand name EMLA.
How It Works
Pharmacodynamics: Prilocaine reversibly binds to sodium channels within neuronal cell membranes. This inhibits the influx of sodium ions, preventing depolarization and blocking nerve impulse conduction, leading to local anesthesia.
Pharmacokinetics:
- Absorption: Prilocaine is well absorbed following injection. Topical application results in slower absorption.
- Metabolism: Prilocaine is primarily metabolized in the liver. This involves the formation of ortho-toluidine, a metabolite capable of inducing methemoglobinemia.
- Elimination: Prilocaine is eliminated via renal excretion, both as unchanged drug and metabolites.
Mode of Action/Receptor Binding: Prilocaine binds to the intracellular portion of voltage-gated sodium channels in nerve axons. This interaction stabilizes the channel’s inactive state, preventing the conformational changes required for channel opening and sodium influx.
Elimination Pathways: Prilocaine undergoes hepatic metabolism via amidases and CYP enzymes. Elimination primarily occurs via renal excretion of metabolites.
Dosage
Standard Dosage
Adults:
For infiltration anesthesia and peripheral nerve block: 1-2 mL (40-80 mg) of a 4% solution subcutaneously. The maximum recommended dose is 600 mg (8 mg/kg) within a 2-hour period.
Children:
- Under 10 years: Maximum 1 mL (40 mg) of a 4% solution, not exceeding 8 mg/kg within 2 hours.
- Over 10 years: 40-80 mg (1-2 mL) of a 4% solution, not exceeding 600 mg (8 mg/kg) within 2 hours. For younger children, Clark’s rule can be used to estimate the appropriate dosage: (weight in pounds x adult dose)/150.
Special Cases:
- Elderly Patients: Dose reduction is often necessary.
- Patients with Renal Impairment: Caution should be used and dosage may need to be adjusted.
- Patients with Hepatic Dysfunction: Methemoglobinemia risk is increased. Close monitoring and dose adjustments are warranted.
- Patients with Comorbid Conditions: Dosage adjustments should be considered for patients with cardiovascular disease, anemia, or other conditions that may impact drug metabolism or increase the risk of adverse effects.
Clinical Use Cases:
Dosage varies considerably depending on the specific procedure and patient factors. Consult relevant medical guidelines for specific dosage recommendations for each procedure.
- Intubation: Prilocaine isn’t typically employed for intubation as a sole anesthetic.
- Surgical Procedures: Dosage is adjusted depending on the procedure’s extent, location, and anticipated duration.
- Mechanical Ventilation: Prilocaine isn’t typically used for ongoing anesthetic purposes during mechanical ventilation.
- Intensive Care Unit (ICU) Use: Prilocaine’s role in continuous nerve blocks necessitates careful monitoring for potential complications.
- Emergency Situations: The use of prilocaine in emergencies should be guided by patient-specific factors, and alternative agents might be preferred.
Dosage Adjustments:
Dosage modification is required in patients with hepatic or renal dysfunction. Methemoglobinemia risk should be assessed, especially in patients with conditions that increase susceptibility. Polymorphisms affecting drug-metabolizing enzymes may also influence dosage.
Side Effects
Common Side Effects:
Swelling, redness, burning or itching at the application site, numbness or tingling of the lips or mouth.
Rare but Serious Side Effects:
Methemoglobinemia (cyanosis, shortness of breath, lightheadedness), allergic reactions (hives, difficulty breathing, swelling of face, lips, tongue, or throat).
Long-Term Effects:
The potential for chronic complications from prolonged use of prilocaine is limited, as it is generally used for short-term procedures. However, potential adverse effects from chronic exposure have not been extensively evaluated.
Adverse Drug Reactions (ADR):
Serious ADRs include methemoglobinemia, allergic reactions, seizures, cardiac arrhythmias, and respiratory depression.
Contraindications
Absolute contraindications include hypersensitivity to prilocaine or other amide-type local anesthetics, and idiopathic or congenital methemoglobinemia. Relative contraindications include significant cardiovascular disease, severe hepatic or renal impairment, and certain blood disorders (e.g., G6PD deficiency).
Drug Interactions
Drugs that can interact with prilocaine include certain antiarrhythmics (e.g., amiodarone), beta-blockers (e.g., propranolol), and drugs that can cause methemoglobinemia. Consult a comprehensive drug interaction database for a complete list.
Pregnancy and Breastfeeding
Prilocaine is categorized as Pregnancy Category B. While animal studies have not shown adverse fetal effects, caution is advised, especially during early pregnancy. Prilocaine is excreted in breast milk, but effects on infants appear minimal after a single dose. Discuss risks and benefits with the patient.
Drug Profile Summary
- Mechanism of Action: Blocks sodium channels, inhibiting nerve impulse conduction.
- Side Effects: Swelling, redness, itching, numbness, methemoglobinemia, allergic reactions.
- Contraindications: Hypersensitivity, methemoglobinemia.
- Drug Interactions: Antiarrhythmics, beta-blockers, drugs causing methemoglobinemia.
- Pregnancy & Breastfeeding: Category B; caution advised. Minimal neonatal effects after single dose.
- Dosage: Adult: 40-80 mg (1-2 mL of 4% solution). Pediatric: <10 years: 40 mg max. >10 years: 40-80 mg. Adjust dose in renal/hepatic impairment.
- Monitoring Parameters: Observe for signs of methemoglobinemia (cyanosis) and allergic reactions.
Popular Combinations
Prilocaine is sometimes combined with epinephrine to prolong the duration of anesthesia. It is also available in a topical formulation with lidocaine.
Precautions
Screen for allergies, hepatic/renal impairment, and methemoglobinemia risk factors. Monitor vital signs during administration. Exercise caution in pregnant/breastfeeding patients, children, and the elderly. Advise patients about potential driving impairment.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Prilocaine?
A: Adult: 40-80 mg (1-2 mL of 4% solution) SC. Pediatric: <10 years: 40 mg max. >10 years: 40-80 mg. Adjust for renal/hepatic impairment.
Q2: What is the maximum dose of prilocaine?
A: 600 mg (8 mg/kg) within a 2-hour period for adults. For children under 10, the maximum dose is 40mg and not to exceed 8 mg/kg within a 2 hour period.
Q3: What are the signs and symptoms of Prilocaine toxicity?
A: Signs of toxicity include methemoglobinemia (cyanosis, shortness of breath), seizures, lightheadedness, confusion, cardiac arrhythmias, and respiratory depression.
Q4: What are the contraindications to using Prilocaine?
A: Known hypersensitivity to prilocaine or other amide-type local anesthetics, idiopathic or congenital methemoglobinemia.
Q5: Can Prilocaine be used during pregnancy?
A: Prilocaine is a pregnancy category B drug. Use with caution, especially during the first trimester.
Q6: Can Prilocaine be used during breastfeeding?
A: Prilocaine is excreted in breast milk, but limited data suggests minimal risk to infants after a single dose. Discuss risks and benefits with the patient.
A: Prilocaine is primarily metabolized in the liver, producing ortho-toluidine, which can induce methemoglobinemia.
Q8: What are the treatment options for methemoglobinemia induced by Prilocaine?
A: Administer methylene blue intravenously. Supportive care, including oxygen therapy, may be necessary.
Q9: What are the drug interactions with Prilocaine?
A: Prilocaine can interact with other drugs that induce methemoglobinemia, such as nitrates and sulfonamides. Caution is also advised with drugs metabolized by CYP enzymes, as prilocaine may inhibit their metabolism.
Q10: What are the common side effects seen at the injection site?
A: Common side effects include pain, swelling, bruising and erythema.
