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KembaraXtra-Emergency and Acute Medicine - Opiate Poisoning
Description: Opiates bind to μ, κ, and δ receptors in the central and peripheral nervous systems, producing analgesia, sedation, and respiratory depression. Both physical and psychological dependence can develop. Peak plasma levels occur within 1–2 hours after oral ingestion, 30–60 minutes after intramuscular use, and seconds to minutes after intravenous or intranasal exposure.
Etiology: Opiate poisoning most commonly results from overuse or abuse of prescription analgesics used for moderate to severe pain. Street preparations may be adulterated with substances such as cocaine, clenbuterol, phencyclidine, strychnine, dextromethorphan, quinine, or scopolamine, which can alter clinical presentation and severity.
Clinical features: Central nervous system effects include somnolence, CNS depression, coma, and seizures. Respiratory depression, apnea, bronchospasm, and noncardiogenic pulmonary edema may occur. Cardiovascular manifestations include hypotension, bradycardia, and palpitations. Gastrointestinal findings include nausea, vomiting, and constipation. Other classic features include miosis and hypothermia. Withdrawal presents with hypertension, tachycardia, tachypnea, abdominal cramps, diarrhea, piloerection, yawning, and agitation. Neonates exposed in utero may develop withdrawal within 12–72 hours after birth, presenting with irritability, tremors, poor feeding, and dehydration. Diphenoxylate toxicity is particularly dangerous in children and may be fatal.
Evaluation: Continuous monitoring of vital signs and respiratory status is essential in significant exposures. Pulse oximetry or arterial blood gases should be obtained, with chest radiography performed for persistent hypoxia, pulmonary edema, or aspiration. Abdominal radiographs are indicated if body packing is suspected. A thorough physical examination should include inspection for occult opioid patches such as fentanyl.
Diagnostic testing: Plasma opioid levels are not clinically useful and treatment is guided by presentation. Urine toxicology screens may fail to detect synthetic opioids such as methadone. An acetaminophen level must be obtained in all suspected oral opioid overdoses due to frequent coformulation and risk of occult toxicity.
Management: Initial management prioritizes airway protection, oxygen supplementation, and circulatory support. Naloxone should be administered promptly to reverse respiratory depression and coma, with cautious low-dose titration in opioid-dependent patients to avoid severe withdrawal. Repeated dosing or continuous infusion may be required for long-acting opioids such as methadone or fentanyl. Endotracheal intubation is indicated if respiratory depression persists despite naloxone. Activated charcoal may be given for recent oral ingestion if the airway is protected. Whole-bowel irrigation with polyethylene glycol is recommended for asymptomatic body packers. Hypotension is treated with intravenous fluids and vasopressors if refractory. Seizures are treated initially with benzodiazepines, followed by phenobarbital if needed. Opioid withdrawal may be managed with clonidine or methadone.
Disposition and follow-up: Admission is required for patients with persistent symptoms, need for repeated naloxone dosing or infusion, body packers, young children after diphenoxylate ingestion, or suspected coingestants. Patients may be discharged if asymptomatic after appropriate observation—6 hours after oral overdose or 4 hours after naloxone administration—and after confirmed elimination of opioid packets when applicable. All patients should receive substance abuse referral, poison prevention counseling for accidental exposures, and psychiatric evaluation for intentional ingestions.
Pearls and pitfalls: Always consider occult acetaminophen poisoning in chronic opioid users. Synthetic and semisynthetic opioids may not appear on standard urine drug screens. Buprenorphine can cause prolonged sedation in children. Used opioid patches still contain clinically significant drug amounts and may cause severe toxicity.
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