Medication Summary
Treatment of cyclic antidepressant (CA) toxicity focuses on airway management, dysrhythmias, seizures, and hypotension. Sodium bicarbonate, benzodiazepines, and norepinephrine are the drugs of choice for these complications.
GI decontaminant
Class Summary
This agent prevents further absorption of drug and other co-ingestants from the GI tract.
Activated charcoal (Liqui-Char)
Emergency treatment in poisoning caused by drugs and chemicals. Network of pores present in activated charcoal adsorbs 100-1000 mg of drug per gram of charcoal. May be administered with or without cathartic (eg, Sorbitol 70%), except in young pediatric patients, where electrolyte imbalance may be of concern. Does not dissolve in water.
For maximum effect, administer within 30 min of ingesting poison.
Cardiovascular agents
Class Summary
Sodium bicarbonate is indicated for QRS intervals greater than 100 milliseconds, seizures, acidosis (pH level < 7), hypotension, cardiac arrest, or dysrhythmia. Antidysrhythmic agents may be helpful. However, avoid certain drugs that exacerbate the cardiac effects of CAs, such as quinidine and procainamide (class IA), flecainide (class IC), and bretylium and amiodarone (class III). Vasopressors are used for the treatment of hypotension not corrected by intravenous fluids.
Sodium bicarbonate (Neut)
First-line therapy for QRS interval >100 milliseconds or if dysrhythmias are present. Correction of acidosis promotes protein binding of CA and improves myocardial contractility. Doses or IV drip may be administered with a pH goal of 7.5-7.55. Monitor and replace potassium as needed to prevent hypokalemia.
Lidocaine (Xylocaine)
Class IB antiarrhythmic that increases electrical stimulation threshold of ventricle, suppressing automaticity of conduction through tissue. Second DOC for CA dysrhythmias.
Norepinephrine (Levophed)
Stimulates beta1- and alpha-adrenergic receptors, which, in turn, increases cardiac muscle contractility, heart rate, and vasoconstriction. As a result, systemic blood pressure and coronary blood-flow increases. DOC to treat hypotension refractory to fluid resuscitation in CA toxicity. Dopamine is second-line and less effective.
Anticonvulsants
Class Summary
Benzodiazepines are preferred for treatment of seizures. Do not use barbiturates in patients with hypotension. Do not use phenytoin in patients with dysrhythmias.
Lorazepam (Ativan)
Sedative hypnotic with short onset of effects and relatively long half-life (longer than diazepam).
By increasing the action of GABA, which is a major inhibitory neurotransmitter in the brain, may depress all levels of CNS, including limbic and reticular formation.
Monitoring patient's blood pressure after administering dose is important. Adjust prn.
Diazepam (Valium)
Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA. Shorter acting than lorazepam.
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.
Phenobarbital (Barbita, Luminal)
Used for seizures not responding to benzodiazepines. Significant respiratory depression; patient may require endotracheal intubation.
Antidysrhythmics, V
Class Summary
Magnesium sulfate has been successfully used in an overdose with refractory ventricular fibrillation. [23] In an animal study, magnesium sulfate converted ventricular tachycardia to sinus rhythm in 9 of 10 rats. [24]
Antidysrhythmics, V
Magnesium sulfate
Given parenterally, magnesium decreases acetylcholine in motor nerve terminals and acts on myocardium by slowing the rate of sinoatrial node impulse formation and prolonging conduction time. May be helpful in treating ventricular fibrillation in TCA toxicity, but further study is needed.
