Acetaminophen (Page 4 of 6)

8.3 Females and Males of Reproductive Potential

Based on animal data use of acetaminophen may cause reduced fertility in males and females of reproductive potential. It is not known whether these effects on fertility are reversible. Published animal studies reported that oral acetaminophen treatment of male animals at doses that are 1.2 times the MHDD and greater (based on a body surface area comparison) result in decreased testicular weights, reduced spermatogenesis, and reduced fertility. In female animals given the same doses, reduced implantation sites were reported. Additional published animal studies indicate that acetaminophen exposure in utero adversely impacts reproductive capacity of both male and female offspring at clinically relevant exposures [see Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

Treatment of Acute Pain

The safety and effectiveness of Acetaminophen Injection for the treatment of acute pain in pediatric patients ages 2 years and older is supported by evidence from adequate and well-controlled studies of Acetaminophen Injection in adults and safety and pharmacokinetic data from adult and 483 pediatric patients across all age groups [see Dosage and Administration (2.3) and Pharmacokinetics (12.3)].

The effectiveness of Acetaminophen Injection for the treatment of acute pain in pediatric patients younger than 2 years of age has not been established.

In patients younger than 2 years, efficacy was not demonstrated in a double-blind, placebo-controlled study of 198 pediatric patients younger than 2 years. Pediatric patients less than 2 years of age, including neonates from 28 to 40 weeks gestational age at birth, were randomized to receive opioid plus acetaminophen or opioid plus placebo. No difference in analgesic effect of intravenous acetaminophen, measured by assessment of reduced need for additional opioid treatment for pain control, was observed.

Treatment of Fever

The safety and effectiveness of Acetaminophen Injection for the treatment of fever in pediatric patients, including premature neonates born at greater than or equal to 32 weeks gestational age is supported by adequate and well-controlled studies of Acetaminophen Injection in adults, clinical studies in 244 pediatric patients 2 years and older, and safety and pharmacokinetic data from 239 patients younger than 2 years including neonates greater than or equal to 32 weeks gestational age.

8.5 Geriatric Use

Of the total number of subjects in clinical studies of acetaminophen, 15% were age 65 and over, while 5% were age 75 and over. 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, but greater sensitivity of some older individuals cannot be ruled out.

8.6 Patients with Hepatic Impairment

Acetaminophen is contraindicated in patients with severe hepatic impairment or severe active liver disease and should be used with caution in patients with hepatic impairment or active liver disease [see Warnings and Precautions (5.1) and Clinical Pharmacology (12) ]. A reduced total daily dose of acetaminophen may be warranted.

8.7 Patients with Renal Impairment

In cases of severe renal impairment (creatinine clearance less than or equal to 30 mL/min), longer dosing intervals and a reduced total daily dose of acetaminophen may be warranted.


Clinical Presentation

In acute acetaminophen overdosage, dose-dependent, potentially fatal hepatic necrosis is the most serious adverse effect. Renal tubular necrosis, hypoglycemic coma, and thrombocytopenia may also occur. Plasma acetaminophen levels greater than 300 mcg/mL at 4 hours after oral ingestion were associated with hepatic damage in 90% of patients; minimal hepatic damage is anticipated if plasma levels at 4 hours are less than 150 mcg/mL or less than 37.5 mcg/mL at 12 hours after ingestion. Early symptoms following a potentially hepatotoxic overdose may include: nausea, vomiting, diaphoresis, and general malaise. Clinical and laboratory evidence of hepatic toxicity may not be apparent until 48 to 72 hours post-ingestion.

Treatment of Overdose

If an acetaminophen overdose is suspected, obtain a serum acetaminophen assay as soon as possible, but no sooner than 4 hours following oral ingestion. Obtain liver function studies initially and repeat at 24-hour intervals. Administer the antidote N-acetylcysteine (NAC) as early as possible. As a guide to treatment of acute ingestion, the acetaminophen level can be plotted against time since oral ingestion on a nomogram (Rumack-Matthew). The lower toxic line on the nomogram is equivalent to 150 mcg/mL at 4 hours and 37.5 mcg/mL at 12 hours. If serum level is above the lower line, administer the entire course of NAC treatment. Withhold NAC therapy if the acetaminophen level is below the lower line.

For additional information, call a poison control center at 1-800-222-1222.


Acetaminophen is a non-salicylate antipyretic and non-opioid analgesic agent. Its chemical name is N-acetyl-p-aminophenol.

Acetaminophen has a molecular weight of 151.16. Its structural formula is:

acetaminophen chemical structure
(click image for full-size original)

Acetaminophen Injection is a sterile, clear, colorless, non pyrogenic, isotonic formulation of acetaminophen intended for intravenous infusion. It has a pH of approximately 5.0 and an osmolality of approximately 290 mOsm/kg.

Each 100 mL contains 1,000 mg Acetaminophen, USP, 3,800 mg Mannitol, USP, 30 mg Sodium Citrate Dihydrate USP, and Water for Injection, USP qs.

Each 50 mL contains 500 mg Acetaminophen, USP, 1,900 mg Mannitol, USP, 15 mg Sodium Citrate Dihydrate USP, and Water for Injection, USP qs.

pH is adjusted with glacial acetic acid.

Not made with natural rubber latex, PVC or DEHP.


12.1 Mechanism of Action

The precise mechanism of the analgesic and antipyretic properties of acetaminophen is not established but is thought to primarily involve central actions.

12.2 Pharmacodynamics

Acetaminophen has been shown to have analgesic and antipyretic activities in animal and human studies. Single doses of acetaminophen up to 3,000 mg and repeated doses of 1,000 mg every 6 hours for 48 hours have not been shown to cause a significant effect on platelet aggregation. Acetaminophen does not have any immediate or delayed effects on small-vessel hemostasis. Clinical studies of both healthy subjects and patients with hemophilia showed no significant changes in bleeding time after receiving multiple doses of oral acetaminophen.

12.3 Pharmacokinetics


The pharmacokinetics of Acetaminophen Injection have been studied in patients and healthy subjects up to 60 years old. The pharmacokinetic profile of Acetaminophen Injection has been demonstrated to be dose proportional in adults following administration of single doses of 500, 650, and 1,000 mg.

The maximum concentration (Cmax ) occurs at the end of the 15-minute intravenous infusion of Acetaminophen Injection. Compared to the same dose of oral acetaminophen, the Cmax following administration of Acetaminophen Injection is up to 70% higher, while overall exposure (area under the concentration time curve [AUC]) is very similar.

Pharmacokinetic parameters of Acetaminophen Injection (AUC, Cmax , terminal elimination half-life [T½ ], systemic clearance [CL], and volume of distribution at steady state [Vss]) following administration of a single intravenous dose of 15 mg/kg in children and adolescents and 1,000 mg in adults are summarized in Table 5.

Table 5. Acetaminophen Injection Pharmacokinetic Parameters
Subpopulations Mean (SD)
AUC0-6h (mcg × h/mL) Cmax (mcg/mL) T½ (h) CL(L/h/kg) Vss(L/kg)
Children 38 (8) 29 (7) 3.0 (1.5) 0.34 (0.10) 1.2 (0.3)
Adolescents 41 (7) 31 (9) 2.9 (0.7) 0.29 (0.08) 1.1 (0.3)
Adults 43 (11) 28 (21) 2.4 (0.6) 0.27 (0.08) 0.8 (0.2)

The concentrations of acetaminophen observed in neonates greater than 32 weeks gestational age at birth treated with 12.5 mg/kg dose are similar to infants, children and adolescents treated with a 15 mg/kg dose, and similar to adults treated with a 1,000 mg dose.

At therapeutic levels, binding of acetaminophen to plasma proteins is low (ranging from 10% to 25%). Acetaminophen appears to be widely distributed throughout most body tissues except fat.

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