Toxicology

Additional serum digoxin concentrations are not recommended after the administration of digoxin

immune Fab. Minimal change in serum concentrations will be expected as the digoxin laboratory test

will still measure the bound, inactive digoxin molecules. Fab-digoxin complexes may stay in the serum

for several days. Repeat serum digoxin concentrations may be checked 24 hours after the initial treatment

if Fab is not administered.

Antidepressants accounted for more than 63,974 single agent toxic exposures and 56 deaths in 2022.

inhibitors (SSRIs) and the tricyclic antidepressants (TCAs).

SSRIs block the reuptake of serotonin at the presynaptic neuron.

Patients with SSRI overdoses are often asymptomatic with self-limiting effects (Emerg Med Clin North

Am 2007;25:477-97). The most common adverse effects may include drowsiness, tremor, altered mental

status, nausea and vomiting, tachycardia, hypotension, seizures, and QRS- or QT-interval prolongation.

TCAs exert many effects, including blocking the reuptake of norepinephrine and serotonin at the

presynaptic neuron, blocking muscarinic cholinergic receptors, blocking antihistamine effect, blocking

the sodium channel, and, to a lesser degree, blocking α-adrenergic receptors.

Individuals with TCA overdoses may present with the following (Emerg Med Clin North Am

1994;12:533-47):

Cardiovascular: Hypo- or hypertension, tachy- or bradycardia, increased QRS or QT interval,

atrioventricular-conduction block, complete heart block

Respiratory: Hypoventilation, crackles, hypoxia

Neurologic: Delirium, lethargy, seizures, coma

There are no specific antidotes for antidepressant overdoses; general supportive care is recommended,

with a focus on ABC.

be administered within the first hour of exposure (Emerg Med Clin North Am 2000;18:637-54).

Administer crystalloid or colloid fluids to maintain BP and HR, with the goal of a mean arterial pressure

>65 mmHg, a SBP greater than 90 mm Hg, and a HR greater than 60 beats/minute.

Norepinephrine or epinephrine may be used if fluid resuscitation alone is unsuccessful.

Dopamine may not be an effective agent because endogenous norepinephrine stores are depleted

in an overdose.

Sodium channel blockade

Alkalinization of blood to a pH of 7.45–7.55 is recommended for the TCAs to resolve metabolic

acidosis and improve cardiac symptoms. Requires frequent monitoring of arterial pH (varies by

effect, but as often as every 15–30 minutes). Sodium load may overcome TCA blockade of sodium

channels by increasing the electrochemical gradient.

Administer sodium bicarbonate

Recommended bolus dose of 1 mEq/kg (minimum: 50 mEq) intravenously

ii.

May repeat bolus every 15 minutes until ECG stabilized or arterial pH goal achieved.