Oral acute (LD50): 4000 mg/kg (mouse), 2210 mg/kg (rat) MSDS.

Overdose

Symptoms of overdose include confusion, drowsiness, blurred vision, tachycardia, nausea, diaphoresis, flushing, headache, and dry mouth.

Carcinogenesis and mutagenesis

In 24-month studies in rats, a dose-related significant increase in gastric carcinoid tumors and ECL cell hyperplasia was seen in male and female animals. Carcinoid tumors have also been found in rats treated with a fundectomy or long-term treatment with other proton pump inhibitors, or high doses of H2-receptor antagonists ^{FDA label}.

Omeprazole showed positive clastogenic effects in an in vitro human lymphocyte chromosomal aberration study, in one of two in vivo mouse micronucleus tests, and in an in vivo bone marrow cell chromosomal aberration test. Omeprazole tested negative in the in vitro Ames test, an in vitro mouse lymphoma cell forward mutation assay, and an in vivo rat liver DNA damage assay ^{FDA label}.

The use in breastfeeding

Limited data indicate that omeprazole may be present in human milk. There is currently no information on the effects of omeprazole on the breastfed infant or production of milk. The benefits of breastfeeding should be considered along with the level of need for omeprazole and any potential adverse effects on the breastfed infant from omeprazole ^{FDA label}.

Effects on fertility

Effects of omeprazole at oral doses up to 138 mg/kg/day in rats (about 34 times an oral human dose) was found to have no impact on fertility and reproductive performance ^{FDA label}.