Analgesic – Antipyretic
Indications And Clinical Uses: As an analgesic for the relief of pain in headache, dysmenorrhea, myalgias and neuralgias; arthritis, sprains, toothache, and fever caused by cold or flu. As an antipyretic when fever accompanies painful conditions.
Contra-Indications: Acetaminophen hypersensitivity.
Precautions: The incidence of gastrointestinal upset is less than after salicylate administration. If a rare sensitivity reaction occurs, discontinue the drug. Hypersensitivity to acetaminophen is usually manifested by a rash or urticaria.
Regular use of acetaminophen has been shown to produce a slight increase in prothrombin time in patients receiving oral anticoagulants. Chronic, high-dose administration of acetaminophen may potentiate the anticoagulant effect of warfarin. Patients stabilized on oral anticoagulants should be advised to limit their intake of acetaminophen to not more than 2 g daily for no more than a few days at a time.
Acetaminophen poisoning can result in severe hepatic damage. Phenobarbital increases the activity of microsomal enzymes which produce a toxic metabolite and therefore acetaminophen’s hepatotoxicity may be enhanced. Thus, concomitant ingestion of phenobarbital may increase the likelihood of liver necrosis in acetaminophen overdose. The chronic ingestion of alcohol may be implicated in the increasing potential for hepatic toxicity.
Lactation: Acetaminophen is excreted in human breast milk, but may be used without danger, in therapeutic dosages, for short-term treatment. Peak concentrations in breast milk occur 1 to 2 hours after a dose.
Pregnancy: Acetaminophen crosses the placenta and is apparently safe for short-term use when therapeutic doses are used.
Adverse Reactions: In therapeutic doses, acetaminophen is relatively nontoxic. Chronic use of large doses of acetaminophen may produce more significant toxicity.
Hepatic: Hepatic toxicity has been associated with acetaminophen in overdose. Chronic use of high doses, e.g., ³5 g daily for several weeks in adults or 150 mg/kg/day for 2 to 4 days in children, has also been associated with hepatotoxicity. Alcoholics, patients with liver disease, the malnourished and patients taking drugs that induce hepatic microsomal enzymes, may be at increased risk for hepatic toxicity.
Renal: Nephropathy, including papillary renal failure has been reported following consumption of large amounts of acetaminophen. Renal tubular necrosis has been associated occasionally with hepatic injury produced by acetaminophen overdose.
Hematologic: Neutropenia and thrombocytopenia purpura have been reported and rarely agranulocytosis.
Hypersensitivity: Laryngeal edema, angioedema and anaphylactoid reactions may occur rarely.
Symptoms And Treatment Of Overdose: In adults, hepatotoxicity may occur after ingestion of a single dose of more than 7.5 g (adults) or 150 mg/kg (children) of acetaminophen; a dose of 10 g or more is potentially fatal. However, reports have indicated hepatic necrosis with a single dose of 6 g and death occurring with a single dose of 13 g. Nonfatal overdoses of 12.5 to 31.5 g have also been reported.Symptoms: Symptoms during the first 2 days of acute poisoning by acetaminophen do not reflect the potential seriousness of the intoxication. Nausea, vomiting, anorexia and abdominal pain occur during the initial 24 hours and may persist for a week or more. Liver injury may become manifest the second day, initially by elevation of serum transaminase and lactic dehydrogenase activity, increased serum bilirubin concentration and prolongation of prothrombin time. Alkaline phosphatase activity and serum albumin concentration may remain normal. The hepatotoxicity may progress to encephalopathy, coma and death. Liver biopsy reveals centrilobular necrosis with sparing of the periportal area. In nonfatal cases, the hepatic lesions are reversible over a period of weeks or months. Transient azotemia is apparent in most patients and acute renal failure occurs in some. Hypoglycemia may occur, but glycosuria and impaired glucose tolerance have also been reported. Both metabolic acidosis and metabolic alkalosis have been noted; cerebral edema and nonspecific myocardial depression have also occurred.
In addition to hepatic damage, clotting defects, and myocardial damage with ST segment abnormalities, T wave flattening and pericarditis have been reported.
Since acetaminophen is metabolized primarily by the liver, in cases of acute poisoning, prolongation of the plasma half-life beyond 3 hours may be indicative of liver injury. Hepatic necrosis should be anticipated if the half-life exceeds 4 hours, and hepatic coma is likely if the half-life is greater than 12 hours. A single determination of serum acetaminophen concentration is a less reliable predictor of hepatic injury. However, only minimal liver damage has developed when the serum concentration was below 120 µg/mL at 4 hours or less than 50 µg/mL at 12 hours after ingestion of the drug. Encephalopathy should also be anticipated if serum bilirubin concentration exceeds 4 mg/100 mL during the first 5 days.
Treatment: Treatment of acute acetaminophen overdosage is symptomatic; vigorous supportive therapy is essential in severe intoxication. Since the hepatic injury is dose dependent and occurs early in the course of intoxication, procedures to limit continuing absorption of the drug must be initiated promptly. Gastric lavage or emesis can be used if the drug has been recently ingested. Persistent vomiting induced by ipecac may interfere with acetylcysteine administration. If activated charcoal has been administered prior to initiation of acetylcysteine therapy, gastric lavage should be performed before the first dose of oral acetylcysteine is given, as charcoal may interfere with acetylcysteine absorption and reduces its effectiveness.
Although appropriate i.v. administration of cysteine or cysteamine may decrease the risk of acetaminophen-induced hepatic necrosis, these drugs are not readily available in Canada at this time. Current evidence suggests that oral N-acetylcysteine may exert a protective effect against hepatic necrosis. Call the nearest Poison Control Centre for the most recent information on treatment.
Dosage And Administration: Adults: 325 to 650 mg every 4 to 6 hours, not to exceed 4 000 mg/24 hours.
SuppliedSupplied: Caplets: Atasol: Each white, elongated, clear, film-coated, biconvex caplet, bisected on one side and imprinted ATASOL on the other side, contains: acetaminophen 325 mg. Nonmedicinal ingredients: alumina, cellulose, cornstarch, FD&C Blue No. 2, magnesium stearate, polyethylene glycol, povidone, stearic acid and titanium dioxide. Alcohol-, sucrose- and tartrazine-free. Bottles of 24 and 100.
Atasol Forte: Each white, elongated, clear, film-coated, biconvex caplet, imprinted ATASOL on one side and FORTE on the other, contains: acetaminophen 500 mg. Nonmedicinal ingredients: alumina, cellulose, cornstarch, FD&C Blue No. 2, magnesium stearate, polyethylene glycol, povidone, stearic acid and titanium dioxide. Alcohol-, sucrose- and tartrazine-free. Bottles of 24 and 100.
Drops: Each mL of red, fruit-flavored solution contains: acetaminophen 80 mg. Nonmedicinal ingredients: citric acid, dibasic sodium phosphate, FD&C Red No. 2 and No. 40, flavor, glycerin, parabens, polyethylene glycol, sodium cyclamate, sorbitol and sucrose. Alcohol- and tartrazine-free. Energy: 10 kJ (2.4 kcal).
Oral Solution: Each 5 mL of orange, fruit-flavored solution contains: acetaminophen 80 mg. Nonmedicinal ingredients: citric acid, dibasic sodium phosphate, FD&C Yellow No. 6, flavor, parabens, polyethylene glycol, sodium benzoate, sodium cyclamate and sorbitol. Alcohol-, sucrose- and tartrazine-free. Energy: 10 kJ (2.4 kcal).
Tablets: Atasol: Each white, round, biconvex tablet, bisected on one side and imprinted ATASOL in one section and plain on the other side, contains: acetaminophen 325 mg. Nonmedicinal ingredients: cellulose, cornstarch, povidone and stearic acid. Alcohol-, sucrose- and tartrazine-free. Energy: 1.3 kJ (0.3 kcal).
Atasol Forte: Each white, shield-shaped tablet, biconvex, diagonally scored on one side, imprinted ATASOL FORTE and plain on the other side, contains: acetaminophen 500 mg (Atasol Forte). Nonmedicinal ingredients: cellulose, cornstarch, povidone and stearic acid. Alcohol-, sucrose- and tartrazine-free. Energy: 1.3 kJ (0.3 kcal).
ATASOL® Preparations Carter Horner Acetaminophen Analgesic – Antipyretic