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 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. 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. Either isotonic or half-isotonic saline may be used for lavage. Saline cathartics, such as Milk of Magnesia, are useful for hastening the evacuation of unreleased medication. Adrenergic receptor blocking agents are antidotes to pseudoephedrine.