CITANEST PLAIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CITANEST PLAIN (CITANEST PLAIN).
Blocks sodium channels, inhibiting nerve impulse conduction.
| Metabolism | Hepatic via CYP1A2 and amidases to inactive metabolites. |
| Excretion | Prilocaine is metabolized primarily in the liver via amidases, with major metabolites including o-toluidine and N-propylalanine. Approximately 50-70% of the dose is excreted renally as metabolites, with less than 2% excreted unchanged in urine. Biliary/fecal excretion is minimal (<5%). |
| Half-life | The terminal elimination half-life of prilocaine is approximately 1.5 hours in adults with normal hepatic and renal function. In neonates, the half-life may be prolonged to 3-4 hours due to immature hepatic metabolism. This short half-life supports its use for procedures requiring moderate duration of anesthesia. |
| Protein binding | Prilocaine is approximately 55% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | The volume of distribution at steady state is about 1.0-1.5 L/kg, indicating extensive distribution into tissues, including the central nervous system and placenta. |
| Bioavailability | Bioavailability for infiltration and nerve blocks is approximately 100% as the drug is administered directly at the site of action. For epidural administration, systemic absorption yields high bioavailability but is not applicable as a primary measure for local anesthetics. Oral bioavailability is negligible due to extensive first-pass metabolism (<5%). |
| Onset of Action | For infiltration and peripheral nerve blocks, onset occurs within 2-5 minutes. For epidural administration, onset is 5-15 minutes. The rapid onset is attributed to the drug's pKa (7.9) and high lipid solubility. |
| Duration of Action | Duration of anesthesia for infiltration and peripheral nerve blocks is 1-2 hours, depending on dose and vascularity of the site. For epidural use, duration is 30-60 minutes. Addition of epinephrine (not present in Citanest Plain) may prolong duration. |
| Molecular Weight | 220.31 |
Prilocaine 1-2% solution: local infiltration, 1-20 mL of 1-2% (10-400 mg); nerve block, 10-40 mL of 1-2% (100-800 mg); epidural, 15-30 mL of 2% (300-600 mg). Maximum dose: 8 mg/kg (600 mg) as single dose, not to exceed 600 mg without epinephrine.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for mild to moderate renal impairment; use with caution in severe renal impairment (GFR <30 mL/min) due to potential accumulation of metabolites; monitor for methemoglobinemia. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25-50%; Child-Pugh C: contraindicated due to risk of systemic toxicity and methemoglobinemia. |
| Pediatric use | Max dose: 8 mg/kg (5 mg/kg for infants <6 months); typical infiltration: 0.5-2 mg/kg; nerve block: 1-4 mg/kg; monitor for methemoglobinemia especially in neonates and infants. |
| Geriatric use | Reduce dose by 20-40% due to decreased clearance and increased risk of toxicity; use lowest effective dose; monitor for CNS and cardiovascular adverse effects. |
| 1st trimester | Limited human data; animal studies not available or insufficient. Use only if clearly needed. |
| 2nd trimester | No evidence of harm in limited studies; consider risk-benefit. |
| 3rd trimester | May cause fetal bradycardia and neonatal CNS depression if used near term; use caution. |
Clinical note
Comprehensive clinical and safety monograph for CITANEST PLAIN (CITANEST PLAIN).
| Placental transfer | Prilocaine crosses the placenta; detected in fetal blood at concentrations 0.5-1 times maternal levels. |
| Breastfeeding | Prilocaine is excreted into breast milk in small amounts; unlikely to cause adverse effects in nursing infants. However, metabolites may cause methemoglobinemia if accumulated; monitor infant for signs of hypoxia. |
| Lactation Rating |
■ FDA Black Box Warning
Not available (no FDA boxed warning).
| Serious Effects |
History of hypersensitivity to prilocaine or other amide anestheticsSevere methemoglobinemia (e.g., G6PD deficiency, NADH-methemoglobin reductase deficiency)Anemia (relative contraindication due to risk of methemoglobinemia)Severe hepatic impairment
| Precautions | Risk of cardiac arrest and arrhythmias with high doses, Allergic reactions to amide-type anesthetics, Methemoglobinemia, especially in neonates |
| Food/Dietary | No specific food interactions are reported with prilocaine. However, patients should avoid alcohol before and after the procedure as it may increase the risk of side effects or impair recovery. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category C. No adequate studies in pregnant women. In animal studies, lidocaine (active component) caused fetal toxicity at doses 6-7 times the maximum human dose. Risk cannot be ruled out. First trimester: Use only if clearly needed. Second and third trimesters: May cause fetal bradycardia and acidosis if large doses are administered paracervically. |
| Fetal Monitoring | Monitor maternal vital signs (blood pressure, heart rate, respiratory rate) and ECG. Fetal heart rate monitoring during paracervical block. Monitor for signs of systemic toxicity (CNS excitation, seizures, arrhythmias). |
| Fertility Effects | No evidence of impaired fertility in animal studies. In humans, no known adverse effects on fertility. Local anesthetics are not expected to affect reproductive function. |
| Clinical Pearls |
| Citanest Plain (prilocaine) is an intermediate-acting amide local anesthetic. It has a slightly slower onset than lidocaine but a longer duration. Due to its vasodilatory effects, it is often used with epinephrine in Citanest Forte. Plain prilocaine is associated with a risk of methemoglobinemia, especially in doses >600 mg. Avoid in patients with congenital or idiopathic methemoglobinemia. Monitor for cyanosis and check methemoglobin levels if suspected. Also note cross-allergy with other amide anesthetics is rare but possible. Doses should be reduced in hepatic impairment. |
| Patient Advice | This medication is a local anesthetic used to numb a specific area for procedures. · You may experience temporary numbness, tingling, or loss of sensation in the treated area. · Do not drive or operate machinery until the numbness has fully worn off. · Report any signs of an allergic reaction such as rash, itching, or difficulty breathing immediately. · Avoid applying heat or rubbing the area until sensation returns to prevent injury. · Inform your doctor if you have a history of blood disorders, especially methemoglobinemia. · If you develop bluish skin or lips, or feel unusually tired or short of breath, seek emergency care. |