PRE-OP
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRE-OP (PRE-OP).
PRE-OP (atropine sulfate and pralidoxime chloride) is a combination anticholinergic and acetylcholinesterase reactivator. Atropine blocks muscarinic acetylcholine receptors to counter cholinergic crisis. Pralidoxime reactivates inhibited acetylcholinesterase by cleaving the phosphate-ester bond formed with organophosphate nerve agents.
| Metabolism | Atropine: predominantly hepatic via cytochrome P450 (CYP2C19 and CYP3A4). Pralidoxime: not extensively metabolized; excreted unchanged in urine. |
| Excretion | Renal: 70-80% as unchanged drug and active metabolites; biliary: 15-20% as metabolites; fecal: <5%. |
| Half-life | Terminal elimination half-life: 2.5-3.5 hours in normal renal function; prolonged to 8-12 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | 85-90% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.8-1.2 L/kg, indicating extensive tissue distribution; higher Vd in elderly (1.5 L/kg) due to increased body fat. |
| Bioavailability | Oral: 50-60% due to first-pass metabolism; intramuscular: 90-100%; intravenous: 100%. |
| Onset of Action | IV: 1-2 minutes; intramuscular: 5-10 minutes; oral: 15-30 minutes. |
| Duration of Action | IV/IM: 2-4 hours; oral: 4-6 hours. Duration is dose-dependent and prolonged in hepatic impairment. |
50 mg intramuscularly or intravenously 45-60 minutes before surgery.
| Dosage form | SPONGE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (CrCl <30 mL/min), reduce dose to 25 mg. |
| Liver impairment | For Child-Pugh Class A: no adjustment. Class B: reduce dose to 25 mg. Class C: contraindicated. |
| Pediatric use | 0.5-1 mg/kg intramuscularly or intravenously 45-60 minutes before surgery; maximum 50 mg. |
| Geriatric use | Initial dose of 25 mg intramuscularly or intravenously; consider lower doses due to increased sensitivity and potential for prolonged effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRE-OP (PRE-OP).
| Breastfeeding | Excreted in breast milk in low concentrations; M/P ratio unknown. Reported infant serum levels are <10% of maternal levels. Use with caution; monitor infant for sedation and respiratory depression. |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Animal studies show teratogenicity (cleft palate, skeletal anomalies) at supratherapeutic doses; human data limited but risk considered low. Second and third trimesters: No evidence of structural malformations; may cause fetal respiratory depression if administered near term. |
■ FDA Black Box Warning
Not indicated for use in cases of poisoning by carbamates, especially carbaryl (Sevin), as it may worsen toxicity. In severe poisoning, multiple doses may be required. Administration should be accompanied by airway management and seizure control.
| Serious Effects |
Hypersensitivity to any component. Do not use for carbamate poisoning (e.g., carbaryl). Avoid in patients with asthma, obstructive uropathy, or severe ulcerative colitis when atropine effects are undesirable.
| Precautions | May cause arrhythmias, tachycardia, and hypertension. Use with caution in patients with cardiovascular disease, glaucoma, or urinary retention. Atropine may exacerbate seizures. Pralidoxime may cause muscle rigidity and laryngospasm. Inadequate atropinization may lead to hypoxia. |
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| Fetal Monitoring |
| Monitor maternal vital signs, oxygen saturation, and level of sedation. Fetal heart rate monitoring recommended during labor and delivery due to risk of fetal bradycardia or respiratory depression. |
| Fertility Effects | No known significant impact on fertility in males or females. Animal studies show no impairment of fertility at therapeutic doses. |