The oral LD50 of nitroglycerin in rats is 105 mg/kg and the LD50 of the intravenous form in rats is 23.2 mg/kg.^L7105

Nitrate overdosage can result in following conditions: severe hypotension, persistent throbbing headache, vertigo, palpitation, visual disturbance, flushing and perspiring skin (later becoming cold and cyanotic), nausea and vomiting (possibly with colic and even bloody diarrhea), syncope (especially in the upright posture), methemoglobinemia with cyanosis and anorexia, initial hyperpnea, dyspnea and slow breathing, slow pulse (dicrotic and intermittent), heart block, increased intracranial pressure with cerebral symptoms of confusion and moderate fever, paralysis and coma followed by clonic convulsions, and possibly death due to circulatory collapse.^L38369

Methemoglobinemia can rarely occur at conventional doses of organic nitrates. This condition is dose-related and it can be even more pronounced in patients with genetic abnormalities of hemoglobin that favor methemoglobin formation. Methemoglobinemia can be managed with the administration of methylene blue unless the patient has a known G-6-PD deficiency.^L38369

There are no known antidotes to an overdose of nitroglycerin, and it is not known whether its metabolites can be removed from the circulation.L38369,L7099 Hypotension associated with nitroglycerin overdose can be managed with different symptomatic and supportive measures, including the elevation of the lower limbs, administration of intravenous saline or other fluids to maintain central fluid volume, and administration of oxygen and artificial ventilation. Gastric lavage may be used in case of ingestion of excess nitroglycerin.^L38369