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Toxicity, Sympathomimetic: Treatment & Medication
Updated: Mar 24, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Prehospital Care
- Managing the airway and controlling agitation are the two main prehospital treatment concerns. Many patients with sympathomimetic poisoning present in an agitated state. In these cases, physical and/or chemical restraint may be required.
- A rapid bedside blood sugar test (eg, Accu-Chek) should be performed to rule out hypoglycemia. Hypoglycemia should be treated if detected.
Emergency Department Care
- General supportive care is the main treatment measure for sympathomimetic toxicity because no antidote exists. Assessment of the airway, breathing, and circulation immediately is recommended. In addition, close monitoring of the vital signs is recommended.
- Sympathomimetic toxicity is frequently associated with significant agitation, thus necessitating the use of physical restraints and chemical sedation. However, physically restrained patients with sympathomimetic-associated agitation or hyperthermia have an associated significant risk of sudden death. The liberal use of chemical sedation in such instances is strongly recommended.
- Benzodiazepines (eg, Valium) are the safest first approach in calming sympathomimetic-poisoned patients. They should be administered frequently in titrated doses.
- Consider gastric decontamination for oral ingestions of sympathomimetic agents. Gastric decontamination is associated with subsequent vomiting and aspiration. Thus, airway control is strongly recommended prior to any gastric decontamination.
- In addition, the patient's airway, breathing, circulation, and agitation should be stabilized before performing GI decontamination.
- It is imperative to measure the core temperature of sympathomimetic poisoned patients. If hyperthermia is present, standard cooling measures should be initiated. Controlling agitation significantly helps in cooling a hyperthermic patient.
- Hypertension unresponsive to sedation should be treated with a rapidly acting and easily titrated agent (eg, sodium nitroprusside).
- Seizures should be rapidly controlled with benzodiazepines and/or barbiturates. Obtaining a CT scan of the brain for all sympathomimetic toxic patients who seize, develop a focal neurologic deficit, or experience a severe headache with or without accompanying hypertension is recommended.
Consultations
- Consultation from the regional poison control center or a local medical toxicologist (certified by the American Board of Medical Toxicology and/or the American Board of Emergency Medicine) for additional information and patient care recommendations is recommended.
- Prolonged critical care management often is required for the numerous complications that may occur with the severe overdose (eg, hyperthermia, seizures, advanced respiratory distress syndrome [ARDS], renal failure, rhabdomyolysis, CNS dysfunction).
Medication
Treatment of sympathomimetic toxicity is focused on controlling agitation, managing seizure activity, and treating hypertension unresponsive to sedation. The most accepted pharmacologic option for controlling agitation is the use of benzodiazepines. Butyrophenones lower the seizure threshold, increase the risk of hyperthermia, and may prolong the QT interval (eg, droperidol); the use of butyrophenones is NOT recommended. Sympathomimetic-induced seizures should be treated with benzodiazepines or barbiturates (eg, phenobarbital). Hypertension should be managed with a short-acting, easily titrated agent (eg, nitroprusside) if it is not controlled with benzodiazepine-induced sedation.
Benzodiazepines and other sedatives
Used for controlling sympathomimetic-induced agitation.
Diazepam (Valium)
Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA.
Individualize dosage and increase cautiously to avoid adverse effects. Easily titrated with a long half-life.
Adult
0.2 mg/kg IV at 2 mg/min; not to exceed 20 mg (as a single dose); may repeat
Pediatric
0.2-0.5 mg/kg IV
<5 years: not to exceed 5 mg
>5 years: not to exceed 10 mg
Increases toxicity of benzodiazepines in CNS with coadministration of phenothiazines, cimetidine, barbiturates, alcohols, and MAOIs
Documented hypersensitivity; narrow-angle glaucoma
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution with other CNS depressants, low albumin levels, or hepatic disease (may increase toxicity); monitor for respiratory depression and hypotension
Lorazepam (Ativan)
Sedative hypnotic with short onset of effects and relatively long half-life.
By increasing the action of GABA, a major inhibitory neurotransmitter in the brain, may depress all levels of CNS, including limbic and reticular formation.
Excellent when patient requires sedation for more than 24 h.
Adult
0.044 mg/kg (2-4 mg) IV; titrate to effect
Status epilepticus: 4 mg IV over 2-5 min; may repeat second dose in 10-15 min if prn; not to exceed 8 mg/dose
Pediatric
Infants and children: 0.1 mg/kg IV slowly over 2-5 min; repeat in 10-15 min at 0.05 mg/kg prn; not to exceed 4 mg/dose
Adolescents: 0.07 mg/kg IV slowly over 2-5 min; repeat in 10-15 min prn; not to exceed 4 mg/dose
Toxicity of benzodiazepines in CNS increases when used concurrently with alcohol, phenothiazines, barbiturates, and MAOIs
Documented hypersensitivity; preexisting CNS depression, hypotension, and narrow-angle glaucoma
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in renal or hepatic impairment, myasthenia gravis, organic brain syndrome, or Parkinson disease; monitor for respiratory depression with high or repeated doses; contains benzyl alcohol, which may be toxic to infants in high doses
Midazolam (Versed)
Used as alternative in termination of refractory status epilepticus. Because water soluble, takes approximately 3 times longer than diazepam to peak EEG effects. Thus, clinician must wait 2-3 min to fully evaluate sedative effects before initiating procedure or repeating dose. Has twice the affinity for benzodiazepine receptors than diazepam. May be administered IM if unable to obtain vascular access.
Adult
0.01-0.05 mg/kg (usually 0.5-4 mg; up to 10 mg) IV slowly over several min; may repeat q10-15min until adequate response achieved
Pediatric
<32 weeks: 0.5 mcg/kg/min IV infusion
>32 weeks: 1 mcg/kg/min IV infusion
Children: 0.05-0.2 mg/kg IV over 2-3 min, followed by 1-2 mcg/kg/min continuous infusion
Status epilepticus (refractory to standard therapy), >2 months and children: 0.15 mg/kg IV, followed by continuous infusion of 1 mcg/kg/min IV; titrate upward q5min until seizures controlled
Sedative effects may be antagonized by theophyllines; narcotics, cimetidine, ethanol, and erythromycin may accentuate sedative effects because of decreased clearance; reduce dose of thiopental by 15% when using together
Documented hypersensitivity; preexisting hypotension, narrow-angle glaucoma, and sensitivity to propylene glycol (diluent)
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in congestive heart failure, pulmonary disease, renal impairment, hepatic failure, neuromuscular disease, hypotension, and patients >60 y; monitor for respiratory depression with high or repeated doses; consider lower dosages with organic brain syndrome and patients who may have inhibition of benzodiazepine metabolism and clearance (eg, using nicotine, taking cimetidine)
Phenobarbital (Barbita, Luminal)
Interferes with transmission of impulses from thalamus to cortex of brain. Used for sympathomimetic-induced seizure unresponsive to diazepam.
Adult
15-20 mg/kg IV load
Pediatric
Administer as in adults
May decrease effects of chloramphenicol, digitoxin, corticosteroids, carbamazepine, theophylline, verapamil, metronidazole, and anticoagulants (patients stabilized on anticoagulants may require dosage adjustments if added to or withdrawn from their regimen); coadministration with alcohol may produce additive CNS effects and fatality; chloramphenicol, valproic acid, and MAOIs may increase toxicity; rifampin may decrease effects; induction of microsomal enzymes may result in decreased effects of oral contraceptives in women (must use additional contraceptive methods to prevent unwanted pregnancy); menstrual irregularities also may occur
Documented hypersensitivity; severe respiratory disease, marked impairment of liver function, and nephritic patients
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
In prolonged therapy, evaluate hematopoietic, renal, hepatic, and other organ systems; caution in fever, hyperthyroidism, diabetes mellitus, and severe anemia because adverse reactions can occur; caution in myasthenia gravis and myxedema; monitor for respiratory depression and hypotension
Cardiovascular agents
Control sympathomimetic-induced hypertension.
Nitroprusside (Nitropress)
Rapidly acting, easily titrated antihypertensive. Produces vasodilation and increases inotropic activity of the heart. At higher dosages, may exacerbate myocardial ischemia by increasing heart rate.
Adult
0.3 mcg/kg/min IV; titrate to effect
Pediatric
Administer as in adults
None reported
Documented hypersensitivity; subaortic stenosis, idiopathic hypertrophic and atrial fibrillation or flutter; sildenafil (Viagra) use within previous 24 h
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in increased intracranial pressure, hepatic failure, severe renal impairment, and hypothyroidism; in renal or hepatic insufficiency, nitroprusside levels may increase and can cause cyanide toxicity; sodium nitroprusside has the ability to lower blood pressure and, thus, should be used only in patients with mean arterial pressures >70 mm Hg
Nitroglycerin (Deponit, Nitrostat)
Causes relaxation of vascular smooth muscle by stimulating intracellular cyclic guanosine monophosphate production, resulting in a decrease in blood pressure.
May administer bolus of 12.5-25 mcg before continuous infusion.
Initial infusion rate of 10-20 mcg/min may be increased 5-10 mcg/min q5-10min until desired clinical or hemodynamic response is achieved.
Infusion rates of 500 mcg/min have occasionally been required.
Adult
400 mcg SL or 5 mcg/min IV; titrate to effect
Pediatric
Not established
Aspirin and indomethacin may increase nitrate serum concentrations; marked symptomatic orthostatic hypotension may occur with coadministration of calcium channel blockers (dose adjustment of either agent may be necessary); concurrent use with DHE may increase toxicity of both agents
Documented hypersensitivity; severe anemia, hypovolemia, constrictive pericarditis or pericardial effusion, hypertrophic cardiomyopathy, shock, postural hypotension, head trauma, closed-angle glaucoma, cerebral hemorrhage, and sildenafil (Viagra) use within previous 24 h
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in coronary artery disease, low systolic blood pressure, glaucoma, hepatic disease, and hyperthyroidism
More on Toxicity, Sympathomimetic |
| Overview: Toxicity, Sympathomimetic |
| Differential Diagnoses & Workup: Toxicity, Sympathomimetic |
 Treatment & Medication: Toxicity, Sympathomimetic |
| Follow-up: Toxicity, Sympathomimetic |
| References |
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References
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Further Reading
Keywords
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