Salicylate toxicity may result from acute ingestion (overdose) or chronic intoxication. The early signs of salicylic overdose (salicylism), including tinnitus (ringing in the ears), occur at plasma concentrations approaching 200 mcg/mL. Plasma concentrations of aspirin above 300 mcg/mL are clearly toxic. Severe toxic effects are associated with levels above 400 mcg/mL. A single lethal dose of aspirin in adults is not known with certainty but death may be expected at 30 g. For real or suspected overdose, contact a Poison Control Center immediately.
Signs and SymptomsIn acute overdose, severe acid-base and electrolyte disturbances may occur and are complicated by hyperthermia and dehydration. Respiratory alkalosis occurs early while hyperventilation is present, but is quickly followed by metabolic acidosis.
TreatmentTreatment consists primarily of supporting vital functions, increasing salicylate elimination, and correcting the acid-base disturbance. Gastric emptying or lavage is recommended as soon as possible after ingestion, even if the patient has vomited spontaneously. After lavage or emesis, administer activated charcoal, as a slurry, if less than 3 hours have passed since ingestion.
Severity of aspirin intoxication is determined by measuring the blood salicylate level. Monitor acid-base status with serial blood gas and serum pH measurements. Maintain fluid and electrolyte balance.
In severe cases, hyperthermia and hypovolemia are the major immediate threats to life. Replace fluid intravenously and correct acidosis. Monitor plasma electrolytes and pH to promote alkaline diuresis of salicylate if renal function is normal. Glucose may be required to control hypoglycemia.
Hemodialysis and peritoneal dialysis can reduce the body aspirin content. In patients with renal insufficiency or in cases of life-threatening intoxication, dialysis is usually required. Exchange transfusion may be indicated in infants and young children.
Acetylsalicylic acid is contraindicated:
The following is a list of adverse reactions that have been reported in the literature for products containing low dose aspirin.
Central Nervous System: Agitation, cerebral edema, coma, confusion, dizziness, headache, lethargy, seizures.
Fluid and Electrolyte: Hyperkalemia, metabolic acidosis, respiratory alkalosis.
Gastrointestinal: Dyspepsia, hepatic enzyme elevation, hepatitis, Reye's Syndrome
Renal: Interstitial nephritis, papillary necrosis, proteinuria, renal insufficiency and failure.
Acetylsalicylic acid is indicated to:
Use immediate-release aspirin, not Acetylsalicylic acid in situations where a rapid onset of action is required (such as acute treatment of myocardial infarction or before percutaneous coronary intervention).
The dose-response relationship for Acetylsalicylic acid and immediate release (IR) aspirin towards COX-1 inhibition was characterized by examining the inhibition of serum TXB2 and urine 11dehydro-TXB2 at 24 h following a single dose. Doses over the range of 20 mg to 325 mg for Acetylsalicylic acid and 5 mg to 81 mg for IR aspirin respectively were studied. Half-maximal inhibition of serum TXB2 and urine 11-dehydro-TXB2 occurred with doses of Acetylsalicylic acid (ID50) about 2-fold the dose of immediate release (IR) aspirin. Based on this relationship, the pharmacodynamic effect of Acetylsalicylic acid 162.5 mg is similar to that attained with IR aspirin 81 mg. The mean inhibition of serum TXB2 following Acetylsalicylic acid (82%) is lower when compared to IR aspirin 81 mg (93%) following the first dose. However, upon repeat administration, near maximal inhibition of serum TXB2 is achieved, similar to what is achieved following repeated daily doses of IR aspirin.
Following oral administration, Acetylsalicylic acid exhibits extended release of aspirin from the encapsulated microparticles, thereby prolonging the absorption of aspirin across the GI tract compared to IR aspirin (Figure 1). Once absorbed, aspirin is metabolized, distributed, and excreted in a manner similar to that of aspirin absorbed from IR dosage forms.
Figure 1: Mean acetylsalicylic acid concentration-time profile following single dose administration of 162.5 mg Acetylsalicylic acid or 81 mg immediate release ASA
Following administration of Acetylsalicylic acid, the time to reach peak plasma concentration of aspirin is slightly longer compared to following IR aspirin dosage form. Median Tmax for Acetylsalicylic acid is about 2 h when compared to 1 h following IR aspirin (see Figure 1). The mean Cmax for Acetylsalicylic acid is approximately 35% of that following IR aspirin 81 mg. The area under the plasma concentration-time curve for aspirin following administration of Acetylsalicylic acid is approximately 70% of that following IR aspirin. The rate of Acetylsalicylic acid absorption is dependent on food, alcohol, and gastric pH.
DistributionThe volume of distribution of usual doses of aspirin in normal subjects averages approximately 170 mL/kg of body weight.
MetabolismAspirin is rapidly hydrolyzed in the plasma to salicylic acid such that plasma levels of aspirin following Acetylsalicylic acid administration are essentially undetectable 4-8 hours after dosing. In contrast to immediate release aspirin, measurable levels of salicyclic acid at 24 hours following a single dose of Acetylsalicylic acid were observed. Salicylic acid is primarily conjugated in the liver to form salicyluric acid, a phenolic glucuronide, an acyl glucuronide, and a number of minor metabolites.
EliminationThe mean plasma half-life of aspirin may range from 20 to 60 min. Following therapeutic doses, approximately 10% is found excreted in the urine as salicylic acid, 75% as salicylic acid, and 10% phenolic and 5% acyl glucuronides of salicylic acid.
Included as part of the PRECAUTIONS section.
PRECAUTIONS Risk Of BleedingAcetylsalicylic acid increases the risk of bleeding. Risk factors for bleeding include the use of other drugs that increase the risk of bleeding (e.g., anticoagulants, antiplatelet agents, and chronic use of NSAIDs).
Peptic Ulcer DiseaseAcetylsalicylic acid may cause gastric ulceration and bleeding. Avoid Acetylsalicylic acid in patients with active peptic ulcer disease.
Fetal ToxicityAcetylsalicylic acid can cause fetal harm when administered to a pregnant woman. Maternal aspirin use during later stages of pregnancy may cause low birth weight, increased incidence for intracranial hemorrhage in premature infants, stillbirths and neonatal death. Because NSAIDs may cause premature closure of the fetal ductus arteriosus, avoid Acetylsalicylic acid in the third trimester of pregnancy.
Nonclinical Toxicology Carcinogenesis, Mutagenesis, Impairment Of FertilityNo carcinogenesis, mutagenesis or impairment of fertility studies were conducted with Acetylsalicylic acid. Aspirin is not considered to be genotoxic or carcinogenic. Studies with oral aspirin in pregnant rats demonstrated the occurrence of fetal malformations at oral doses at or above 250 mg/kg [Human equivalent dose (HED) 40 mg/kg].
Use In Specific Populations PregnancyAvoid use during the third trimester of pregnancy because NSAIDs such as Acetylsalicylic acid may cause premature closure of the fetal ductus arteriosus. Salicylate products have also been associated with alterations in maternal and neonatal hemostasis mechanisms, decreased birth weight, and with perinatal mortality.
Labor And DeliveryAvoid Acetylsalicylic acid 1 week prior to and during labor and delivery because it can result in excessive blood loss at delivery. Prolonged gestation and prolonged labor due to prostaglandin inhibition have been reported.
Nursing MothersBecause of the potential for serious adverse reactions in nursing infants from Acetylsalicylic acid, choose either to discontinue Acetylsalicylic acid or discontinue nursing.
Pediatric UseSafety and effectiveness in pediatric patients have not been established.
Geriatric UseIn a large collaborative overview of aspirin for vascular event prevention, including over 14000 patients over 65 years of age, no overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients.
Hepatic ImpairmentAvoid Acetylsalicylic acid in patients with severe hepatic insufficiency.
Renal ImpairmentAvoid Acetylsalicylic acid in patients with severe renal failure (glomerular filtration rate less than 10 mL/minute).
The recommended dose of Acetylsalicylic acid is one capsule (162.5 mg) once daily. Take the capsules with a full glass of water at the same time each day.
Swallow Acetylsalicylic acid capsules whole. Do not cut, crush or chew capsules.
Do not take Acetylsalicylic acid 2 hours before or 1 hour after consuming alcohol.
