PRALIDOXIME CHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRALIDOXIME CHLORIDE (PRALIDOXIME CHLORIDE).
Pralidoxime chloride is a cholinesterase reactivator. It reactivates acetylcholinesterase that has been inactivated by phosphorylation due to organophosphate or carbamate exposure by binding to the organophosphate moiety and cleaving the enzyme-phosphate bond, thereby restoring enzymatic activity. It also has direct antimuscarinic and antinicotinic effects at high doses.
| Metabolism | Hepatic metabolism is minimal; pralidoxime is primarily excreted unchanged by the kidneys via glomerular filtration and tubular secretion. The elimination half-life is approximately 1-2 hours, but may be prolonged in renal impairment. |
| Excretion | Renal: >90% as unchanged drug and metabolites (including pyridone and pyridinium derivatives). Biliary/fecal: <5%. |
| Half-life | Terminal elimination half-life is approximately 1.5–2.5 hours in adults. In renal impairment, half-life may be prolonged up to 5–6 hours, necessitating dose adjustment. |
| Protein binding | Minimal (<5% bound to plasma proteins, primarily albumin). |
| Volume of Distribution | Approximately 0.7–1.0 L/kg (suggests distribution into extracellular fluid and some tissue binding). |
| Bioavailability | Intravenous: 100%. Intramuscular: approximately 80–100%. Oral: <10% due to first-pass metabolism and poor absorption. |
| Onset of Action | Intravenous: within 1–2 minutes. Intramuscular: 5–15 minutes. Oral: not clinically relevant (poor and erratic absorption). |
| Duration of Action | Plasma levels decline rapidly; duration of clinical effect is about 1–2 hours. Repeated dosing every 3–4 hours is needed to sustain reactivation of inhibited acetylcholinesterase. |
1-2 g IV over 15-30 minutes, may repeat in 1 hour if muscle weakness persists, then every 10-12 hours as needed; typically given with atropine. Maximum dose: 2 g/hour or 12 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment needed for single-dose therapy; for continuous infusion in renal impairment (CrCl < 10 mL/min): reduce dose by 50% or extend interval to every 12 hours. |
| Liver impairment | No specific adjustment required; caution in severe liver disease due to limited data, monitor hepatic function. |
| Pediatric use | 20-50 mg/kg IV over 15-30 minutes, may repeat in 1 hour if needed, then every 10-12 hours; maximum single dose 2 g, maximum rate 50 mg/kg/hour. |
| Geriatric use | Use adult dosing with caution; monitor renal function and reduce dose if CrCl < 50 mL/min as per adult renal adjustment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRALIDOXIME CHLORIDE (PRALIDOXIME CHLORIDE).
| Breastfeeding | No data on pralidoxime excretion in human milk. M/P ratio unknown. Given the short half-life and urgent indication, breastfeeding can be resumed after maternal stabilization and elimination, but caution is advised. Consider temporary interruption during therapy. |
| Teratogenic Risk | Pralidoxime is an antidote used for organophosphate poisoning. Data in pregnant women are limited. Animal studies have not shown teratogenicity at clinically relevant doses. The risk to the fetus must be weighed against the life-threatening maternal condition. No specific trimester risks are defined; use is justified in emergency poisoning regardless of trimester. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to pralidoxime or any component of the formulation.","Poisoning by carbamates (e.g., carbaryl) in the absence of medical supervision due to potential for increased toxicity; however, it may be used in carbamate poisoning with caution."]
| Precautions | ["Should be used in conjunction with atropine; atropine should be administered first to control muscarinic symptoms.","Rapid intravenous administration may cause tachycardia, laryngospasm, muscle rigidity, and transient neuromuscular blockade.","Use with caution in patients with myasthenia gravis; may precipitate cholinergic crisis.","Renal impairment may require dose adjustment due to reduced clearance.","Pregnancy: Use only if clearly needed; safety not established."] |
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| Fetal Monitoring | Monitor maternal vital signs, oxygen saturation, cardiac rhythm, and neuromuscular function. Fetal heart rate monitoring should be performed if viable gestation. Monitor for signs of organophosphate toxicity and response to therapy (e.g., atropine effect). Assess for maternal adverse effects: dizziness, blurred vision, tachycardia, muscle rigidity. |
| Fertility Effects | No studies on human fertility effects. Animal studies have not reported reproductive impairment at therapeutic doses. Impact unlikely given acute use. |