Tuesday, December 7, 2021

Acetaminophen: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions

Acetaminophen: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions


Classification and Category
Chemical class: Nonsalicylate, paraaminophenol derivative
Therapeutic class: Antipyretic, nonopioid analgesic
Pregnancy category: B
Abenol, Acephen, Apo-Acetaminophen, Atasol, Feverall, Mapap, Ofirmev, Tempra, Tylenol, Tylenol Arthritis Pain, Tylenol Junior Meltaways, Tylenol Extra Strength,  Tylenol Children’s Meltaways

General Information

Azithromycin belongs to a group of drugs known as non-opioid analgesics, used to treat mild to moderate pain in adults and pediatric patients 2 years of age and older, treating moderate to severe pain with analgesics additional opioids in adults and pediatric patients 2 years of age and older, reduction of fever in adults and pediatric patients

Acetaminophen can cause adverse reactions such as headache, insomnia, nausea and vomiting. Less frequently reported side effects included anxiety, dyspnoea, fatigue, hypersensitivity reaction, hypertension, hypokalaemia, hypotension, increased aspartate aminotransferase, infusion site pain, muscle spasms, peripheral edema and trismus


It can block peripheral pain impulses that occur in response to inhibition of prostaglandin synthesis; has no anti-inflammatory properties; The antipyretic action derives from the inhibition of prostaglandins in the CNS (hypothalamic heat-regulating center)

Therapeutic Effect

Results in antipyresis. Produces analgesic effect

Availability (Rx)

Caplets: 325 mg, 500 mg, 650 mg. Elixir: 160 mg/5 mL. Injection, Solution
(Ofirmev): 1,000 mg/100 mL glass vial. Liquid (Oral): 160 mg/5 mL, 500
mg/5 mL, 500 mg/15 mL. Solution (Oral Drops): 80 mg/0.8 mL. Suppository:
80 mg, 120 mg, 325 mg, 650 mg. Suspension: 160 mg/5 mL. Tablets: 325 mg,
500 mg. Tablets (Chewable): 80 mg. Tablets (Orally Disintegrating): 80 mg,
160 mg
Caplets:(Extended-Release [Tylenol Arthritis Pain]): 650 mg


Mild to moderate pain or fever, headache, arthralgia, dental pain, dysmenorrhea, myalgia, osteoarthritis
Unlabeled uses: Migraine


Pregnancy (B), (C) IV; breastfeeding, geriatric patients, anemia, renal/hepatic (liver) disease, chronic alcoholism

Make sure to tell your doctor if:
• Sensitivity to acetaminophen
• Severe renal impairment
• Alcohol dependency
• Hepatic impairment, or active hepatic disease
• Chronic malnutrition and hypovolemia (Ofirmev)
• Limit dose to less than 4 g/day

Indications and Dosages

 To relieve mild to moderate pain from headache, muscle ache, backache, Common cold, minor arthritis, toothache, or menstrual cramps; to reduce fever

• Adult. 325 to 650 mg / 4 to 6 hr, or 1,000 mg t.i.d. or q.i.d., or 2 E.R. caplets every 8 hr. Maximum: 4,000 mg daily
• Children over age 14. 650 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 12 to 14. 640 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children age 11. 480 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 9 to 10. 400 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 6 to 8. 320 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 4 to 5. 240 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 2 to 3. 160 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children age 1. 120 mg every 4 hr.
Maximum: 5 doses in 24 hr.
• Children ages 4 to 11 months. 80 mg every
4 hr. Maximum: 5 doses in 24 hr.
• Children ages 0 to 3 months. 40 mg every
4 hr. Maximum: 5 doses in 24 hr.

• Adults and adolescents. 650 mg every 4 to
6 hr. Maximum: 4,000 mg daily.
• Children ages 6 to 12. 325 mg every 4 to 6
hr. Maximum: 2,600 mg daily.
• Children ages 3 to 6. 120 to 125 mg every
4 to 6 hr. Maximum: 720 mg daily.
• Children ages 1 to 3. 80 mg every 4 hr.
• Children ages 3 to 11 months.
80 mg every 6 hr.


It is rapidly and completely absorbed from the gastrointestinal tract; rectal absorption variable. Protein binding: 20%-50%. Widely distributed to most body tissues. Metabolized in liver; excreted in urine. Removed by hemodialysis. Half-life: 1-4 h (half-life is increased in those with hepatic (liver) disease, elderly, neonates; decreased in children)


PO route

• Administer to the patient crushed or whole; chewable tablets can be chewed; do not crush or chew the EXT REL product
• Give with food or milk to decrease gastric symptoms; give 30 minutes before or 2 hours after meals; absorption can slow down
• Shake the susp well; check all product concentrations carefully;  check elixir, liquid, suspension concentration carefully; susp and cups are bioequivalent

Intermittent IV infusion route

• No further dilution is required, do not add other drugs to the vial or infusion device
• For doses equal to a single vial, a ventilated IV set can be used to be administered directly from the vial; for doses less than a single vial, withdraw the dose and place in an empty sterile syringe, plastic IV container or glass bottle, infuse for 15 minutes
• Discard the unused portion, once the seal is broken or the vial has penetrated or transferred to another container, give within 6 hours


Hypersensitivity.In addition, people with active alcoholism, liver disease or viral hepatitis do not recommend self-treatment, which increases the risk of hepatotoxicity


Individual drugs

• Alcohol (chronic use), hepatotoxic medications (e.g., phenytoin), and any CYP2E1 inducers: May increase risk of hepatotoxicity with prolonged high dose or single toxic dose.
• Warfarin: Most data indicate significant interaction not likely; however, any time a new medication, such as acetaminophen, is added and taken regularly, INR monitoring is recommended.

Drug classifications

 Barbiturates, hydantoins: decreased effect; increased hepatotoxicity
 NSAIDs, salicylates: increased renal adverse reactions

Drug/laboratory tests

• Interference: 5-HIAA Increase: Potassium, LFTs, bilirubin, LDH, pro-time
 Decrease: WBC, RBC, platelets, Hgb / Hct; albumin, magnesium, phosphate (pediatrics)


• Increase: heptatotoxicity—St. John’s wort, due to acetaminophen metabolism
• Increase: hepatotoxicity—echinacea (rare)

Side effects

GI: Abdominal pain, hepatotoxicity, nausea, vomiting; hepatotoxicity,
hepatic seizure (overdose), GI
GU: Renal failure (high, prolonged doses)
HEME: Hemolytic anemia (in case with long-term use), leukopenia, neutropenia, pancytopenia, thrombocytopenia
SKIN: Jaundice, rash, urticaria Other: Angioedema, hypoglycemic coma
SYST: Hypersensitivity
TOXICITY: Cyanosis, anemia, neutropenia, jaundice, pancytopenia, CNS stimulation, delirium followed by vascular collapse, seizures, coma, death

Nursing considerations

Baseline assessment

• If given for analgesia, evaluate the onset, type, location and duration of pain
• Effect of drug is reduced if full pain response recurs prior to next dose. Assess for fever
• Assess LFT in pts with chronic usage or history of hepatic impairment, alcohol abuse


• Assess for clinical improvement and relief of pain, fever. 
• Therapeutic serum level: 10–30 mcg/mL;  toxic serum level: greater than 200 mcg/mL. Do not exceed the maximum recommended daily dose: 4 g / day

Equipment must be available for anaphylaxis

• Monitor liver function tests: AST, ALT, bilirubin, creatinine before therapy if long-term therapy is anticipated; may cause hepatic toxicity at doses .4 g/day with chronic use
• Monitor renal function tests: BUN, urine creatinine, occult blood; albumin indicates nephritis
• Monitor blood tests: CBC, PT if patient is on long-term therapy
• Check I&O ratio; decreased production may indicate renal/ kidney failure (long-term therapy)
• Assess for fever and pain: type of pain, intensity, location, duration, temp, diaphoresis
• Assess for chronic poisoning: rapid, weak pulse; dyspnea; cold, clammy extremities; inform the prescriber immediately
• Assess hepatotoxicity: dark urine, claycolored stools, yellowing of skin and sclera; itching, abdominal pain, fever, diarrhea if patient is on long-term therapy
• Assess allergic reactions: if rash, (urticaria) hives occur, product may have to be discontinued


Positive therapeutic result
• Decreased pain, use pain scoring
• Decreased fever

Patient/family teaching

• Teach the patient not to exceed the recommended dose; the elixir, liquid, and suspension come in several concentrations, read label carefully; acute poisoning with liver damage can occur; acute toxicity includes symptoms of nausea, vomiting,and abdominal pain; the prescriber must be informed immediately
• Consult a doctor for use in children younger than 2 years of age, oral use for more than 5 days (children) or more than 10 days (adults) or fever lasting more than 3 days
• Severe and recurrent pain or high and continuous fever may indicate serious illness
• Do not take more than 4g / day (3g / day if using OTC [without prescription]) Actual over-the-counter (OTC) dosing recommendations may vary by product and / or manufacturer
• Advise the patient that toxicity may occur when used with other combination products
• Advise the patient not to use with alcohol, over-the-counter products, or herbs without doctor's approval.
• Teach the patient to recognize the signs of a chronic overdose: bleeding, bruising, malaise, fever, sore throat
• Inform the patient that the urine may turn dark brown due to phenacetin (metabolite of paracetamol)
• That people with diabetes may notice changes in their blood sugar control
• May be used when breastfeeding, short-term

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