PRALIDOXIME CHLORIDE (AUTOINJECTOR)
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRALIDOXIME CHLORIDE (AUTOINJECTOR) (PRALIDOXIME CHLORIDE (AUTOINJECTOR)).
Reactivates acetylcholinesterase inhibited by organophosphate poisoning by binding to the organophosphate moiety.
| Metabolism | Hepatic (glucuronidation) and renal elimination |
| Excretion | Primarily renal excretion of unchanged drug and metabolites; approximately 80-90% of a dose is excreted in urine within 4-6 hours, with 50% as unchanged pralidoxime and the remainder as metabolites (e.g., 1-methyl-2-pyridone-2-aldoxime). Minor biliary/fecal elimination (<10%). |
| Half-life | Terminal elimination half-life is approximately 1.2-2.5 hours in adults with normal renal function. In organophosphate poisoning, prolonged half-life may occur due to redistribution or renal impairment; clinical context: requires repeated dosing or continuous infusion to maintain therapeutic concentrations. |
| Protein binding | Minimal protein binding; approximately 0-10% bound to plasma proteins (albumin). |
| Volume of Distribution | Volume of distribution: 0.6-1.2 L/kg, indicating distribution primarily into extracellular fluid and limited tissue penetration (does not cross blood-brain barrier significantly). Clinical meaning: dosing based on lean body weight; Vd may be smaller in children. |
| Bioavailability | Intramuscular: approximately 100% bioavailability compared to IV. Oral: negligible (<5%) due to poor absorption and first-pass metabolism; not administered orally. |
| Onset of Action | Intramuscular: 5-15 minutes for detectable plasma levels; clinical effect (reversal of nicotinic symptoms) may begin within 10-20 minutes. Intravenous: 1-5 minutes for onset of clinical effect. For autoinjector (IM), onset is similar to IM injection. |
| Duration of Action | Duration of clinical effect is approximately 1-2 hours after a single IM dose due to rapid elimination; repeated doses or continuous IV infusion (e.g., 8-10 mg/kg/h) are often required for sustained effect in severe poisoning. Clinical note: effect on muscarinic symptoms is limited; atropine must be co-administered. |
| Molecular Weight | 172.6 |
1-2 g IV or IM, repeat after 1 hour if muscle fasciculations persist, then every 6-12 hours as needed. Administer as a 5% solution (1g in 20mL) over 5-10 minutes IV; IM into deltoid or anterolateral thigh.
| Dosage form | SOLUTION |
| Renal impairment | No specific GFR-based dose adjustments established; use with caution in severe renal impairment (CrCl <30 mL/min) as drug is renally excreted, consider extended dosing intervals. |
| Liver impairment | No specific Child-Pugh based modifications; dose adjustment not required as hepatic metabolism is minimal. |
| Pediatric use | 20-50 mg/kg IV or IM, not to exceed 1 g per dose; repeat after 1 hour if needed, then every 6-12 hours. Administer IV over 5-10 minutes. |
| Geriatric use | No specific dose adjustment; use standard dosing with caution due to potential decreased renal function, monitor for adverse effects. |
| 1st trimester | Animal studies have not shown teratogenicity. Use only if clearly needed due to life-threatening organophosphate poisoning. |
| 2nd trimester | No evidence of fetal harm; consider maternal benefit in life-threatening poisoning. |
| 3rd trimester | Use cautiously near term due to potential for uterine contractions? (unlikely at doses used). |
Clinical note
Comprehensive clinical and safety monograph for PRALIDOXIME CHLORIDE (AUTOINJECTOR) (PRALIDOXIME CHLORIDE (AUTOINJECTOR)).
| Placental transfer | Crosses placenta in animals; expected in humans due to low molecular weight. |
| Breastfeeding | No data on excretion in human milk. Due to short half-life and indication for life-threatening poisoning, breastfeeding can be resumed after therapy completed. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to pralidoxime or any component of the autoinjector
| Precautions | Use with caution in patients with myasthenia gravis; may precipitate cholinergic crisis or adverse reactions due to rapid reactivation., May cause neuromuscular blockade, especially in patients with neuromuscular disorders., Should be used in conjunction with atropine for organophosphate poisoning. |
| Food/Dietary | None known. |
| Clinical Pearls | Administer as soon as possible after organophosphate exposure; repeat doses may be necessary if atropine is required. Monitor for laryngospasm, muscle rigidity, and tachycardia. Use with caution in myasthenia gravis. In severe poisoning, continuous infusion may be needed. Autoinjector delivers 600 mg IM; do not use if solution is discolored or contains precipitate. |
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| Lactation Rating |
| L3 (Moderately Safe) or 'Probably Compatible' |
| Teratogenic Risk | Pralidoxime chloride is indicated for organophosphate poisoning, a life-threatening condition where the benefit of treatment outweighs potential fetal risks. Animal studies have not demonstrated teratogenic effects, but adequate human studies in pregnant women are lacking. First trimester: theoretical risk, but no human data suggest increased malformations. Second and third trimesters: no evidence of fetal harm from pralidoxime itself; risks are primarily from maternal hypoxia and toxicity of organophosphates. Overall, use when clearly needed for maternal survival. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, respiratory status, and oxygen saturation continuously during treatment. Fetal heart rate monitoring if gestational age permits, due to potential maternal hypoxia or hypotension affecting placental perfusion. Assess for signs of atropine co-administration side effects (e.g., tachycardia, blurred vision). |
| Fertility Effects | No human studies on fertility effects. Animal studies have not shown impaired fertility at clinically relevant doses. Organophosphate poisoning itself may cause reproductive toxicity; treatment with pralidoxime may mitigate these effects by reversing poisoning. |
| Patient Advice | Autoinjector is for emergency use only; seek medical care immediately after administration. · Inject into outer thigh muscle through clothing if necessary; hold for 10 seconds after activation. · Common side effects include dizziness, blurred vision, and injection site pain; report difficulty breathing or chest tightness. · Do not use after expiration date; store at room temperature away from light. |