Celestamine is a combination product and therefore the potential toxicity of each of its components must be considered. Toxicity from a single excessive dose of Celestamine results primarily from the dexchlorpheniramine component. The estimated lethal dose of the antihistamine dexchlorpheniramine maleate is 2.5-5 mg/kg.
Symptoms: Overdosage reactions with conventional (sedating) antihistamines may vary from central nervous system depression (sedation, apnea, diminished mental alertness, cyanosis, arrhythmias, cardiovascular collapse) to stimulation (insomnia, hallucinations, tremors, convulsions) to death. Other signs and symptoms may include dizziness, tinnitus, ataxia, blurred vision and hypotension. In children, stimulation is dominant, as are atropine-like signs and symptoms (dry mouth, fixed, dilated pupils, flushing, fever and gastrointestinal symptoms). Hallucinations, incoordination and convulsions of the tonic-clonic type may occur. In adults, a cycle consisting of depression with drowsiness and coma, and an excitement phase leading to convulsions followed by depression may occur.
A single excessive dose of betamethasone is not expected to produce acute symptoms. Except at the most extreme dosages, a few days of excessive glucocorticosteroid dosing is unlikely to produce harmful results except in patients at particular risk due to underlying conditions or on concomitant medications likely to interact adversely with betamethasone.
Treatment: In the event of overdosage, emergency treatment should be started immediately. Consultation with a poison control center is recommended. Consider standard measures to remove any unabsorbed drug eg, activated charcoal, gastric lavage. Dialysis has not been found helpful. There is no specific antidote. Measures to enhance excretion (urinary acidification, hemodialysis) are not recommended.
Treatment of the signs and symptoms of overdosage is symptomatic and supportive.