Acetaminophen (Paracetamol)

Class and Category

Pharmacologic class: Nonsalicylate, para-aminophenol derivative

Therapeutic class: Antipyretic, nonopioid analgesic

Indications and Dosages

👉   To relieve mild to moderate pain

REGULAR STRENGTH (325 MG): CAPLETS, CAPSULES, CHEWABLE TABLETS, ELIXIR, GELCAPS, LIQUID SOLUTION, SPRINKLES, SUSPENSION, TABLETS

Adults and children 12 yr and over. 640 or 650 mg every 4 to 6 hr, as needed.

Maximum: 3,250 mg (5 doses) in 24 hr.

EXTRA STRENGTH (500 MG) CAPLETS OR TABLETS

Adults. 1,000 mg every 6 hr, as needed. Maximum: 3,000 mg in 24 hr.

8-HR (650 MG) CAPLETS

Adults. 1,300 mg every 8 hr. Maximum: 3,900 mg in 24 hr.

CHEWABLE TABLETS, ORAL SUSPENSION, SYRUP

1. Children age 12 and over weighing 43.5 kg (96 lb) or more. 640 mg every 4 hr, as needed. Maximum: 3,200 mg (5 doses) in 24 hr.
2. Children age 11 weighing 32.6 kg (72 lb) to 43 kg (95 lb). 480 mg every 4 hr, as needed. Maximum: 2,400 mg (5 doses) in 24 hr.
3. Children age 9 to 10 weighing 27 kg (60 lb) to 32 kg (71 lb). 400 mg every 4 hr, as needed. Maximum: 2,000 mg (5 doses) in 24 hr.
4. Children age 6 to 8 weighing 21.5 kg (48 lb) to 26.5 kg (59 lb). 320 mg every 4 hr, as needed. Maximum: 1,600 mg (5 doses) in 24 hr.
5. Children age 4 to 5 weighing 16 kg (35 lb) to 21 kg (47 lb). 240 mg every 4 hr, as needed. Maximum: 1,200 mg (5 doses) in 24 hr.
6. Children age 2 to 3 weighing 10.9 kg (24 lb) to 15.9 kg (35 lb). 160 mg every 4 hr, as needed. Maximum: 800 mg (5 doses in 24 hr.

SUPPOSITORIES

1. Adults and adolescents. 650 mg every 4 to 6 hr, as needed. Maximum: 3,900mg in 24 hr.
2. Children ages 6 to 12. 325 mg every 4 to 6 hr, as needed. Maximum: 1,625 mg in 24 hr.
3. Children ages 3 to 6. 120 mg every 4 to 6 hr, as needed. Maximum: 600 mg in 24 hr.
4. Children ages 1 to 3. 80 mg every 4 to 6 hr, as needed. Maximum: 400 mg in 24 hr.
5. Children ages 6 to 11 months. 80 mg every 6 hr, as needed. Maximum: 320 mg in 24 hr.

👉  To relieve mild to moderate pain; to manage moderate to severe pain with adjunctive opioid analgesics

I.V. INFUSION

1. Adults and adolescents age 13 and over weighing 50 kg (110 lb) or more. 650 mg administered over 15 min every 4 hr, as needed, or 1,000 mg administered over 15 min every 6 hr, as needed. Maximum: 4,000 mg in 24 hr.
2. Adults and children age 2 and over weighing less than 50 kg (110 lb). 12.5 mg/kg administered over 15 min every 4 hr, as needed, or 15 mg/kg (up to 750 mg) administered over 15 min every 6 hr, as needed. Maximum: 75 mg/kg (up to 3,750 mg) in 24 hr.

👉  To Reduce Fever

I.V. INFUSION 

• Adults and adolescents age 13 and over weighing 50 kg (110 lb) or more. 650 mg administered over 15 min every 4 hr, as needed, or 1,000 mg administered over 15 min every 6 hr, as needed. Maximum: 4,000 mg in 24 hr.
• Adults and children age 2 and over weighing less than 50 kg (110 lb). 12.5 mg/kg administered over 15 min every 4 hr, as needed, or 15 mg/kg (up to 750 mg) administered over 15 min every 6 hr, as needed. Maximum: 75 mg/kg (up to 3,750 mg) in 24 hr.
• Infants 29 days to 2 years. 15 mg/kg every 6 hr, as needed. Maximum: 60 mg/kg/day with minimum dosing interval of 6 hr.
• Premature neonates at least 32 weeks gestational age and up to 28 days. 12.5 mg/kg every 6 hr, as needed. Maximum: 50 mg/kg/day with minimum dosing interval of 6 hr.

DOSAGE ADJUSTMENT For patient with severe renal impairment (creatinine clearance 30 ml/min or less), dosing interval increased and total daily dosage reduced. For patient with mild to moderate hepatic impairment, total daily dosage reduced.

Mechanism of Action

Inhibits the enzyme cyclooxygenase, blocking prostaglandin production and interfering with pain impulse generation in the peripheral nervous system.
Acetaminophen also acts directly on temperature-regulating center in the hypothalamus by inhibiting synthesis of prostaglandin E2.

Incompatibilities

Don’t mix parenteral acetaminophen with any other medication. Diazepam and chlorpromazine are physically incompatible with parenteral acetaminophen.

Contraindications

Hypersensitivity to acetaminophen or its components, severe hepatic impairment, severe active liver disease.

Interactions

DRUGS

Anticholinergics: Decreased onset of acetaminophen action 

Barbiturates, Carbamazepine, Hydantoins, Isoniazid, Rifampin, Sulfinpyrazone: Decreased therapeutic effects and increased hepatotoxic effects of acetaminophen

Dasatinib, Imatinib: Possibly increased risk of hepatotoxicity

Lamotrigine: Possibly decreased therapeutic effects of these drugs 

Oral Contraceptives: Decreased effectiveness of acetaminophen

Probenecid: Possibly increased therapeutic effects of acetaminophen

Propranolol: Possibly increased action of acetaminophen

Warfarin: Possibly increased international normalized ratio

Zidovudine: Possibly decreased zidovudine effects

ACTIVITIES

Alcohol use: Increased risk of hepatotoxicity

Adverse Reactions

CNS: Agitation, anxiety, fatigue, fever, headache, insomnia

CV: Hypotension, hypertension, peripheral edema

EENT: Stridor (parenteral form)

ENDO: Hypoglycemic coma

GI: Abdominal pain, constipation, diarrhea, hepatotoxicity, jaundice, nausea, vomiting

GU: Oliguria (parenteral form)

HEME: Hemolytic anemia (with long-term use), leukopenia, neutropenia, pancytopenia, thrombocytopenia

MS: Muscle spasm (parenteral form)

RESP: Parenteral form: atelectasis, dyspnea, plural effusion, pulmonary edema, wheezing

SKIN: Acute generalized exanthematous pustulosis, blisters, pruritus, rash, reddening, Stevens–Johnson syndrome, toxic epidermal necrolysis, urticaria

Other: Anaphylaxis, angioedema, hypersensitivity reactions; for parenteral form: hypoalbuminemia, hypokalemia, hypomagnesemia, hypophosphatemia, injection-site pain Childbearing Considerations

PREGNANCY

• Use of drug at any time during pregnancy may increase risk of attention deficit hyperactivity disorder (ADHD) after birth.
• Use with caution only if benefit to mother outweighs potential risk to fetus.

LACTATION

Drug is present in breast milk.

Patient should check with prescriber before breastfeeding.

Nursing Considerations

• Use acetaminophen cautiously in patients with hepatic impairment or active hepatic disease, alcoholism, chronic malnutrition, severe hypovolemia, or severe renal impairment.
• Know that before and during long-term therapy including parenteral therapy, liver function test results, including AST, ALT, bilirubin, and creatinine levels, as ordered must be monitored because acetaminophen may cause hepatotoxicity. Ensure that the daily dose of acetaminophen from all sources does not exceed maximum daily limits.

• Monitor renal function in patient on long-term therapy. Keep in mind that blood or albumin in urine may indicate nephritis; decreased urine output may indicate renal failure; and dark brown urine may indicate presence of the metabolite phenacetin.
• Store suppositories under 26.6°C (80°F).

WARNING: Do not confuse a dose in milligrams with a dose in milliliters when preparing and administering the parenteral form of acetaminophen. Also, make sure the dose is based on the patient’s weight and infusion pumps are properly programmed.

• Be aware that patients weighing 50 kg (110 lb) or more and requiring 1,000-mg doses of parenteral acetaminophen can have the dose administered by inserting a vented intravenous set through the septum of the 100-ml vial. Further dilution is not required. For doses less than 1,000 mg, the appropriate dose must be withdrawn from the vial and placed into a separate container prior to administration to prevent inadvertent overdose. Place small-volume pediatric doses up to 60 ml in a syringe and administer over 15 minutes using a syringe pump.
• Monitor the end of a parenteral infusion to prevent possibility of air embolism.
• Use parenteral drug within 6 hours once vacuum seal of glass vial has been penetrated or contents transferred to another container.

PATIENT TEACHING

• Tell patient that tablets may be crushed or swallowed whole.
• Know that concentrated infant drops are being phased out and are no longer manufactured, but may still be available.
• Instruct patient to read manufacturer’s label and follow dosage guidelines precisely. Explain that infants and children’s acetaminophen liquid aren’t equal in drug concentration and aren’t interchangeable. Until concentrated infant drops are completely phased out, parents should use extra caution to ensure the correct dose is given with strength being used. Tell them to use only the measuring device that comes with the bottle to help ensure accurate dosage.
• Caution patient not to exceed recommended dosage or take other drugs containing acetaminophen at the same time because of risk of liver damage. Advise him to contact prescriber before taking other prescription or OTC products because they may contain acetaminophen.
• Teach patient to recognize signs of hepatotoxicity, such as bleeding, easy bruising, and malaise, which commonly occurs with chronic overdose.

WARNING: Caution patient that serious skin reactions, although rare, may occur even with first-time use and any time acetaminophen is used, even if no skin reactions occurred with a previous use of drug. Tell patient that if a skin rash, redness, or blisters occur, he should stop using drug and seek emergency treatment immediately.

• Inform patient that acetaminophen may cause reduced fertility in both females and males.