Salicylates are ubiquitous agents found in hundreds of over-the-counter (OTC) medications and in numerous prescription drugs, making salicylate toxicity an important cause of morbidity and mortality. [1, 2, 3, 4]
Salicylates are used as analgesic agents for the treatment of mild to moderate pain. Aspirin is used as an antipyretic and as an anti-inflammatory agent for the treatment of soft tissue and joint inflammation and vasculitides such as acute rheumatic fever and Kawasaki disease. Aspirin is also used to treat acute coronary syndrome. Low-dose aspirin helps to prevent thrombosis.
Acetylsalicylic acid is colorless or white in crystalline, powder, or granular form. The chemical is odorless and is soluble in water. Salicylate is available for ingestion as tablets, capsules, and liquids. Salicylate is also available for topical application, in creams or lotions.
Salicylate ingestion continues to be a common cause of poisoning in children and adolescents. The prevalence of aspirin-containing analgesic products makes these agents, found in virtually every household, common sources of unintentional and suicidal ingestion.
However, the incidence of salicylate poisoning in children has declined because of reliance on alternative analgesics and the use of child-resistant containers. Repackaging has decreased children's accessibility to lethal amounts, and salicylate's association with Reye syndrome has significantly decreased its use.
Still, more than 10,000 tons of aspirin are consumed annually in the United States. Aspirin or aspirin-equivalent preparations (in milligrams) include children's aspirin (80-mg tablets with 36 tablets per bottle), adult aspirin (325-mg tablets), methyl salicylate (eg, oil of wintergreen; 98% salicylate), and Pepto-Bismol (236 mg of non-aspirin salicylate per 15 mL).
Ingestion of topical products containing salicylates (eg, Ben-Gay, salicylic acid [keratolytic], oil of wintergreen or methyl salicylate), can cause severe salicylate toxicity. According to published sources, one teaspoon of 98% methyl salicylate contains as much as 7000 mg of salicylate, the equivalent of nearly 90 baby aspirins and more than 4 times the potentially toxic dose for a child who weighs 10 kg. [5, 6]
Salicylate toxicity has been reported with the topical use of salicylate-containing teething gels in infants. [7] Based on a literature review, Greene et al estimated the allowable daily intake of methyl salicylate to be 11 mg/kg/d. [8]
A comprehensive review of the existing medical literature on methyl salicylate poisoning has determined that it is a relatively common source of pediatric exposure. [9] In younger children, most of these exposures are accidental. In a study of 599 cases of salicylate exposure in children less than 6 years old, the majority of children with signs of salicylate toxicity(metabolic acidosis, tachypnea) were exposed to liquid preparations. [10] Intentional ingestions are much more common in adolescents.
The prevalence of alternative medicines and the popularity of herbs and traditional medicine formulae are increasing in North America. Many of these medicines may contain salicylate. Therefore, consider salicylate poisoning when topical herbal medicinal oil is involved.
Percy Medicine contains bismuth subsalicylate as the active ingredient and is a constipation reliever. A case of neonatal salicylate poisoning due to the use of this medicine to relieve colic has been reported. [11] Percy Medicine is available OTC, and parents should be educated that salicylate-containing products are not routinely recommended for children aged 1 year or younger.
Although concentrations of salicylate persist following ingestion of aspirin tablets, it has been shown that salicylate concentrations typically decline following ingestion of salicylate as acetylsalicylicpowder. In one study, salicylate concentrations increased or changed insignificantly in 50% of patients who had ingested tablets, but following powder ingestions, concentrations declined in 94% of cases. [12]
Phases and symptoms of salicylate toxicity
The acid-base, fluid, and electrolyte abnormalities seen with salicylate toxicity can be grouped into three phases. (See Presentation and Workup.)
Phase 1 of the toxicity is characterized by hyperventilation resulting from direct respiratory center stimulation, leading to respiratory alkalosis and compensatory alkaluria. Potassium and sodium bicarbonate are excreted in the urine. This phase may last as long as 12 hours.
In phase 2, paradoxical aciduria occurs when sufficient potassium has been lost from the kidneys in the presence of continued respiratory alkalosis. This phase may begin within hours and last 12-24 hours.
Phase 3 includes dehydration, hypokalemia, and progressive metabolic acidosis. This phase may begin 4-6 hours after ingestion in a young infant or 24 hours or more after ingestion in an adolescent or adult.
Nausea, vomiting, diaphoresis, and tinnitus [13] are the earliest signs and symptoms of salicylate toxicity. Other early symptoms and signs are vertigo, hyperventilation, tachycardia, and hyperactivity. As toxicity progresses, agitation, delirium, hallucinations, convulsions, lethargy, and stupor may occur. Hyperthermia is an indication of severe toxicity, especially in young children.
Treatment
A high index of suspicion of salicylate toxicity is necessary, with prompt recognition of clinical signs and symptoms of salicylate poisoning, such as tinnitus, hyperventilation, tachycardia, and metabolic acidosis. [3] Early treatment can prevent organ damage and death. Treatments include stabilizing the ABCs as necessary, limiting absorption, enhancing elimination, correcting metabolic abnormalities, and providing supportive care. No specific antidote is available for salicylates.No specific antidote is available for salicylate toxicity. However, alkalinization of the urine and serum with sodium bicarbonate is crucial to management. [14]
