Receiving Nitroglycerin almost instantly relieves the pain syndrome due to lightning action on the nervous system structures. Abuse of this drug and unauthorized increase in dosage is fraught with fatal consequences. Nitroglycerin is a medicine that helps relax the blood vessels leading to the heart. It is used to prevent and treat chest pain. Nitroglycerin overdose occurs when someone takes more than the normal or recommended amount of this medicine. Other answers here are correct about the effect of drinking nitroglycerin, but a few details. The lethal dose for an average size adult is about 2 grams (or 2 mL, less than 1/2 a teaspoon), too small to make much of a swallow. The estimated adult oral lethal dose of nitroglycerin is 200 mg to 1,200 mg. Infants may be more susceptible to toxicity from nitroglycerin. Consultation with a poison center should be considered. Consultation with a poison center should be considered. The estimated adult oral lethal dose of nitroglycerin is 200 mg to 1,200 mg. Infants may be more susceptible to toxicity from nitroglycerin. Consultation with a poison center should be considered. Consultation with a poison center should be considered. Contraindications and side effects. Lethal dose of nitroglycerin for a person of average age and weight will be 2.0 grams. But an overdose of nitroglycerin is dangerous not only taking a lethal amount of active ingredient. Nitroglycerin relaxes the muscles of the gastrointestinal tract, so it is used for diseases of the biliary tract. In rare cases, nitroglycerin is prescribed for embolism (blockage) of the central retinal artery. Detailed Nitroglycerin dosage information for adults. Includes dosages for Hypertension, Myocardial Infarction, Angina Pectoris and more; plus renal, liver and dialysis adjustments. If after taking nitroglycerin pain syndrome does not pass for 15 minutes, you should immediately call the ambulance. This phenomenon is characteristic of acute myocardial infarction, coronary syndrome. The estimated adult oral lethal dose of nitroglycerin is 200 mg to 1,200 mg. Infants may be more susceptible to toxicity from nitroglycerin. Consultation with a poison center should be considered. Consultation with a poison center should be considered.