OVERDOSE
Since Guaifenex® PSE 60 (guaifenesin pseudoephedrine extended-release tablets) Extended-release Tablets contain two pharmacologically
different compounds, treatment of overdosage should be based upon the symptomatology
of the patient as it relates to the individual ingredients. Treatment of acute
overdosage would probably be based upon treating the patient for pseudoephedrine
toxicity which may manifest itself as excessive CNS stimulation resulting in
excitement, tremor, restlessness, and insomnia. Other effects may include tachycardia,
hypertension, pallor, mydriasis, hyperglycemia and urinary retention. Severe
overdosage may cause tachypnea or hyperpnea, hallucinations, convulsions or
delirium, but in some individuals there may be CNS depression with somnolence,
stupor or respiratory depression. Arrhythmias (including ventricular fibrillation)
may lead to hypotension and circulatory collapse. Severe hypokalemia can occur,
probably due to a compartmental shift rather than a depletion of potassium.
No organ damage or significant metabolic derangement is associated with pseudoephedrine
overdosage. Overdosage with guaifenesin is unlikely to produce toxic effects
since its toxicity is much lower than that of pseudoephedrine.
The LD50 of pseudoephedrine (single oral dose) has been reported
to be 726 mg/kg in the mouse, 2206 mg/kg in the rat and 1177 mg/kg in the rabbit.
The toxic and lethal concentrations in human biologic fluids are not known.
Urinary excretion increases with acidification and decreases with alkalinization
of the urine. There are few published reports of toxicity due to pseudoephedrine
and no case of fatal overdosage has been reported. Guaifenesin, when administered
by stomach tube to test animals in doses up to 5 grams/kg, produced no signs
of toxicity.
Since the action of extended-release products may continue for as long as 12
hours, treatment of overdosage should be directed toward reducing further absorption
and supporting the patient for at least that length of time. Gastric emptying
(Syrup of Ipecac) and/or lavage is recommended as soon as possible after ingestion,
even if the patient has vomited spontaneously. Either isotonic or half-isotonic
saline may be used for lavage. Administration of an activated charcoal slurry
is beneficial after lavage and/or emesis if less than 4 hours have passed since
ingestion. Saline cathartics, such as Milk of Magnesia, are useful for hastening
the evacuation of unreleased medication.
Adrenergic receptor blocking agents are antidotes to pseudoephedrine. In practice,
the most useful is the beta-blocker propranolol which is indicated when there
are signs of cardiac toxicity. Theoretically, pseudoephedrine is dialyzable
but procedures have not been clinically established.
In severe cases of overdosage, it is essential to monitor both the heart (by
electrocardiograph) and plasma electrolytes, and to give intravenous potassium
as indicated. Vasopressors may be used to treat hypotension. Excessive CNS stimulation
may be counteracted with parenteral diazepam. Stimulants should not be used.
CONTRAINDICATIONS
This product is contraindicated in patients with hypersensitivity to guaifenesin,
or with hypersensitivity or idiosyncrasy to sympathomimetic amines which may
be manifested by insomnia, dizziness, weakness, tremor or arrhythmias.
Sympathomimetic amines are contraindicated in patients with severe hypertension,
severe coronary artery disease and patients on monoamine oxidase (MAO) inhibitor
therapy (see DRUG INTERACTIONS section).