The Lowest published toxic dose (TDLo) of tetryzoline in children following oral administration is 175 mg/kg. Oral LD₅₀ is 785 mg/kg in rats and 345 mg/kg in mice. Intraperitoneal LD₅₀ is 122 mg/kg in rats and 110 mg/kg in mice. Subcutaneous LD₅₀ is 500 mg/kg in rats.^L32609

Overdose following accidental oral ingestion in children may lead to profound sedation, possibly accompanied by profuse sweating, hypotension, and shock. In adults, hypertension, bradycardia, drowsiness, and rebound hypotension may be observed, in addition to a shock-like syndrome with hypotension and bradycardia.^L32599 In one case, cardiovascular effects persisted for 36 hours after unintentional ingestion of tetrahydrozoline.^A7045 Profound sedation has occurred in adults following accidental oral ingestion due to poisoning.^A231764

Overdose should be managed with supportive treatment, with the patient kept warm. Fluid maintenance therapy may be initiated if necessary. The respiratory rate dropping to 10 or below should be responded with oxygen therapy and respiratory assistance. Blood pressure should be carefully monitored to prevent a hypotensive crisis.^L32599 There is no known antidote to tetryzoline overdose; however, one case report illustrates the successful use of naloxone in reversing the clinical signs and symptoms of tetryzoline overdose in a child. Naloxone has been used to revere clonidine overdose. The exact mechanism of action of naloxone as an antidote is not fully understood; however, it is understood that clonidine and tetryzoline work to inhibit central sympathetic outflow by activating alpha-2 adrenoceptors and inducing endogenous opiate release, which naloxone works to antagonize.^A231779