Ingestion of aspirin and similar drugs (salicylates) can lead to rapid (acute) poisoning due to an overdose. The dose necessary to cause acute poisoning, however, is quite large. A person weighing about 150 pounds would have to consume more than 30 325-miligram tablets to develop even mild poisoning. An acute aspirin overdose, therefore, is seldom accidental.
Gradual aspirin poisoning can develop unintentionally by taking aspirin repeatedly at much lower doses. Children with fever who are given only slightly higher than the prescribed dose of aspirin for several days may develop poisoning, although children are rarely given aspirin to treat fever because of the risk of development of Reye syndrome (see Miscellaneous Disorders in Infants and Young Children: Reye Syndrome). None of the over-the-counter cough and cold preparations sold in the United States for children contains aspirin; most contain either acetaminophen or ibuprofen. Adults, many of them elderly, can develop poisoning gradually after several weeks of use. The dosage of aspirin recommended for people with coronary artery disease to reduce the risk of heart attack (1 baby aspirin, ½ of an adult aspirin, or 1 full adult aspirin daily) is too small to cause gradual poisoning.
The most toxic form of salicylate is oil of wintergreen (methyl salicylate). Methyl salicylate is a component of products such as liniments and solutions used in hot vaporizers. A young child can die from swallowing less than 1 teaspoonful of pure methyl salicylate. Far less toxic are over-the-counter products containing bismuth subsalicylate (used to treat infections of the digestive tract), which can cause poisoning after several doses.
The first symptoms of acute aspirin poisoning are usually nausea and vomiting followed by rapid breathing, ringing in the ears, and sweating. Later, if poisoning is severe, the person can develop light-headedness, fever, drowsiness, hyperactivity, confusion, seizures, destroyed muscle tissue (rhabdomyolysis), kidney failure, and difficulty breathing.
The symptoms of gradual aspirin poisoning develop over days or weeks. Drowsiness, subtle confusion, and hallucinations are the most common symptoms. Light-headedness, rapid breathing, shortness of breath, fever, dehydration, low blood pressure, a low oxygen level in the blood (hypoxia), a buildup of lactic acid in the blood (lactic acidosis), fluid in the lungs (pulmonary edema), seizures, and brain swelling can develop.
Diagnosis and Treatment
A blood sample is taken to measure the precise level of aspirin in the blood. Measurement of the blood pH (amount of acid in the blood) and the level of carbon dioxide or bicarbonate in the blood also can help doctors determine the severity of poisoning. Tests are usually repeated several times during treatment to reveal whether the person is recovering.
Activated charcoal is given as soon as possible and reduces aspirin absorption. For moderate or severe poisoning, fluids containing sodium bicarbonate are given by vein. Unless there is kidney damage, potassium is added to the fluid. This mixture moves aspirin from the bloodstream into the urine. If the person's condition is worsening despite other treatments, hemodialysis (which uses an artificial kidney [dialyzer] to filter the poisons—see Dialysis: Hemodialysis) can remove aspirin, other salicylates, and acids from the blood. Other symptoms such as fever or seizures are treated as necessary.
Last full review/revision February 2013 by Gerald F. O'Malley, DO; Rika O'Malley, MD