LD50

Oral LD50 was 830 mg/kg in male Swiss mice 24 hours after being administered mirtazapine.^F4597

Overdose information

Activated charcoal should be administered during an overdose to absorb excess mirtazapine. General supportive therapy should be employed, including maintenance of an adequate airway, oxygen therapy, and ventilation therapy. Vital signs and cardiac rhythm must be monitored. It is not advisable to induce vomiting. Gastric lavage with a large-bore orogastric tube with proper protection of the airway is recommended ^{FDA label}. There is no antidote for mirtazapine available currently.^{FDA label} Consider the possibility of mirtazapine combined with other drugs in an overdose and ensure to contact the local poison control center for guidance on management.^{FDA label}

Carcinogenesis

At higher than normal doses, mirtazapine increased the incidence of hepatocellular adenomas and carcinomas in male mice. The highest doses administered to the mice were about 20 and 12 times the maximum recommended human dose (MRHD).^{FDA label} Hepatocellular tumors and thyroid follicular adenoma/cystadenomas in male rats occurred at an increased rate at a higher mirtazapine dose (60 mg/kg/day). In female rats, both the medium (20 mg/kg/day) and higher (60 mg/kg/day) doses of mirtazapine increased the rate of hepatocellular adenomas.^{FDA label} The relevance of these findings in humans is not known at this time.^{FDA label}

Impairment of Fertility

Mirtazapine was administered to rats at doses reaching 100 mg/kg (equivalent to 20 times the maximum recommended human dose) in a fertility study. There was no impact on mating and conception, however, there was a disturbance of reproductive (estrous) cycling at higher doses. These doses were measured to be at least 3 times the maximum recommended human dose. Loss of fetus before implantation in the uterus occurred when doses equivalent to 20 times the maximum recommended dose were administered.^{FDA label}

Use in pregnancy

This drug is categorized as a pregnancy category C drug. No adequate studies in pregnant women have been conducted. In rats, an increased rate of post-implantation demise occurred with mirtazapine administration. Additionally, an increase in deaths of rat pups during the first 3 days of lactation with a decrease in pup birth weight was noted. Studies on animals are not always relevant to human response. Mirtazapine should be used during pregnancy only if the clinical need outweighs the possible risks to the fetus.^{FDA label}

Use in nursing

Whether this drug is excreted in human milk is unknown.^{FDA label} Many drugs are found excreted in human breast milk, therefore caution is advised if this drug is used during nursing.^{FDA label}