LD₅₀ Values

Mouse: 2 g/kg (Oral), 57 mg/kg (IV), 134 mg/kg (IP), 400 mg/kg (SC)^L6316

Rat: 2 g/kg (Oral), 77 mg/kg (IV), 600 mg/kg (SC)^L6316

Rabbit: 50 mg/kg (IV)^L6316

Carcinogenicity & Mutagenicity

Studies in rats and mice at doses of 300 mg/kg/day, equivalent to 150 times maximum recommended human dose, for durations of 18 and 24 months showed no carcinogenicity.label One study in rats at doses of 500-1500 mg/kg/day, 250-750 times maximum human dose, resulted in increases benign adrenal medullary tumors in both sexes and increase mammary fibroadenomas in females.

Atenolol showed no mutagenicity in the Ames test using S. typhinarium, dominant lethal test in mice, or in vivo cytogenetics test in chinese hamster ovary cells.label

Reproductive Toxicity

No adverse effects on fertility were observed in either male or female mice after receiving doses of 200 mg/kg/day, equivalent to 200 times the maximum human dose. In humans, atenolol is known to cross the placenta and fetuses exposed to the drug have been reported to be smaller than expected considering gestational age. Embryo-fetal resorption has been observed in rats at doses of 50mg/kg/day, 50 times the max human dose, but not in rabbits at doses of 25mg/kg/day.label

Lactation

Atenolol appears in breast milk at a ratio of 1.5-6.8 to plasma concentrations.label It has been estimated that infant exposure occurs at 5.7-19.2% maternal weight-adjusted dosage.^L6313 Effects in infants include bradycardia, hypothermia, and lethargy.