Since pseudoephedrine HCl w/ guaifenesin 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 the 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. 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. In severe cases of overdose, it is recommended to monitor the patient in an intensive care setting.

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 alkalization 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 t.b. to test animals in doses up to 5 grams/kg, produced no signs of toxicity.

Since the action of sustained 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 where there are signs of cardiac toxicity. Theoretically, pseudoephedrine is dialyzable but procedures have not been clinically established.

Pseudoephedrine HCl w/ guaifenesin tablets are contraindicated in patients with hypersensitivity to guaifenesin, or with hypersensitivity or idiosyncrasy to sympathomimetic amines which may be manifested by insomnia, dizziness, weakness and tremor or arrhythmias.

Sympathomimetic amines are contraindicated in patients with severe hypertension, severe coronary artery disease and patients on monoamine oxidase inhibitor (MAOI) therapy and for 14 days after stopping M.O. therapy. (See DRUG INTERACTIONS.)

Bookmark this page: