Theophylline Toxicity in Emergency Medicine Medication

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Class Summary

GI decontaminants are empirically used to minimize systemic absorption of the toxin. They may only be of benefit if administered within 1-2 h of ingestion.

Activated charcoal (Liqui-Char)

Prevents absorption by adsorbing drug in intestine. Multidose charcoal may interrupt enterohepatic recirculation and enhance elimination by enterocapillary exsorption. Theoretically, by constantly bathing the GI tract with charcoal, the intestinal lumen serves as a dialysis membrane for reverse absorption of drug from intestinal villous capillary blood into intestine. Supplied as an aqueous mixture or in combination with a cathartic (usually sorbitol 70%).

Class Summary

Persistent vomiting may interfere with decontamination.

Ondansetron (Zofran)

5HT-3 antagonist acting both on the vagus nerve peripherally and at the CTZ in the CNS.

Ranitidine (Zantac)

H2 antagonist that may be a useful adjunct in reducing emesis volume.

Metoclopramide (Reglan)

Works as antiemetic by blocking dopamine receptors in the chemoreceptor trigger zone of the CNS.

Prochlorperazine (Compazine)

May relieve nausea and vomiting by blocking postsynaptic mesolimbic dopamine receptors through anticholinergic effects and depressing reticular activating system.

In addition to antiemetic effects, has the advantage of augmenting hypoxic ventilatory response, acting as a respiratory stimulant at high altitude.

Droperidol (Inapsine)

Neuroleptic agent that may reduce emesis by blocking dopamine stimulation of chemoreceptor trigger zone.

Class Summary

These agents are used to terminate seizures and for seizure prophylaxis in high-risk patients. They help to alleviate nausea and vomiting and decrease tremors and anxiety induced by theophylline.

Diazepam (Valium)

Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA.

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.

Monitoring blood pressure after administering dose is important. Adjust prn.

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.

Phenobarbital (Barbita, Luminal)

Interferes with transmission of impulses from thalamus to cortex of brain.

Class Summary

Alpha-agonists are used to treat persistent hypotension not responding to fluid challenges. Beta-blockers are used for treating severe tachycardia with ischemia or severe hypotension.

Phenylephrine (Neo-Synephrine)

Strong postsynaptic alpha-receptor stimulant with little beta-adrenergic activity that produces vasoconstriction of arterioles. Increases peripheral venous return.

Esmolol (Brevibloc)

Short-acting IV cardioselective beta-adrenergic blocker with no membrane depressant activity. Half-life of 8 min allows for titration to effect and quick discontinuation prn.

Norepinephrine (Levophed)

For protracted hypotension following adequate fluid-volume replacement. Stimulates beta1- and alpha-adrenergic receptors, which, in turn, increases cardiac muscle contractility and heart rate as well as vasoconstriction. As a result, systemic blood pressure and coronary blood-flow increases.

After obtaining a response, the rate of flow should be adjusted and maintained at a low normal blood pressure, such as 80-100 mm Hg systolic, sufficient to perfuse vital organs.