Analgesic, Anti-inflammatory, and Antipyretic Drugs

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Analgesic, Anti-inflammatory, and Antipyretic Drugs: Acetaminophen, Acetylsalicylic Acid

Synonym/acronym: Acetaminophen (Acephen, Aceta, Apacet, APAP 500, Aspirin Free Anacin, Banesin, Cetaphen, Dapa, Datril, Dorcol, Exocrine, FeverALL, Genapap, Genebs, Halenol, Little Fevers, Liquiprin, Mapap, Myapap, Nortemp, Pain Eze, Panadol, Paracetamol, Redutemp, Ridenol, Silapap, Tempra, Tylenol, Ty-Pap, Uni-Ace, Valorin); Acetylsalicylic acid (salicylate, aspirin, Anacin, Aspergum, Bufferin, Easprin, Ecotrin, Empirin, Measurin, Synalgos, ZORprin, ASA).

Common use

To assist in monitoring therapeutic drug levels and detect toxic levels of acetaminophen and salicylate in suspected overdose and drug abuse.


Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Immunoassay)
DrugTherapeutic Range Conventional UnitsConversion to SI unitsSI UnitsHalf-LifeVolume of DistributionProtein BindingExcretion
Acetaminophen5–20 mcg/mLSI units = Conventional Units × 6.6233–132 micromol/L1–3 hr0.95 L/kg20%–50%85%–95% hepatic; metabolites, renal
Salicylate10–30 mg/dLSI units = Conventional Units × 0.0730.7–2.2 mmol/L2–3 hr0.1–0.3 L/kg90%–95%1° hepatic; metabolites, renal


Acetaminophen is used for headache, fever, and pain relief, especially for individuals unable to take salicylate products or who have bleeding conditions. It is the analgesic of choice for children less than 13 yr old; salicylates are avoided in this age group because of the association between aspirin and Reye’s syndrome. Acetaminophen is rapidly absorbed from the gastrointestinal tract and reaches peak concentration within 30 to 60 min after administration of a therapeutic dose. It can be a silent killer because, by the time symptoms of intoxication appear 24 to 48 hr after ingestion, the antidote is ineffective. Acetylsalicylic acid (ASA) is also used for headache, fever, inflammation, and pain relief. Some patients with cardiovascular disease take small prophylactic doses. The main site of toxicity for both drugs is the liver, particularly in the presence of liver disease or decreased drug metabolism and excretion. Other medications indicated for use in controlling neuropathic pain include amitriptyline and nortriptyline. Detailed information is found in the monograph titled “Antidepressant Drugs (Cyclic): Amitriptyline, Nortriptyline, Protriptyline, Doxepin, Imipramine, Desipramine.”

Many factors must be considered in interpreting drug levels, including patient age, patient weight, interacting medications, electrolyte balance, protein levels, water balance, conditions that affect absorption and excretion, and the ingestion of substances (e.g., foods, herbals, vitamins, and minerals) that can potentiate or inhibit the intended target concentration.

Important note: These medications are metabolized and excreted by the liver and kidneys and are therefore contraindicated in patients with hepatic or renal disease and cautiously advised in patients with renal impairment. Information regarding medication must be clearly and accurately communicated to avoid misunderstanding of the dose time in relation to the collection time. Miscommunication between the individual administering the medication and the individual collecting the specimen is the most frequent cause of subtherapeutic levels, toxic levels, and misleading information used in calculation of future doses. If administration of the drug is delayed, notify the appropriate department(s) to reschedule the blood draw and notify the requesting health-care provider (HCP) if the delay has caused any real or perceived therapeutic harm.

This procedure is contraindicated for



  • Suspected overdose
  • Suspected toxicity
  • Therapeutic monitoring

Potential diagnosis

Increased in

  • Acetaminophen
    • Alcoholic cirrhosis (related to inability of damaged liver to metabolize the drug)
    • Liver disease (related to inability of damaged liver to metabolize the drug)
    • Toxicity
  • ASA
    • Toxicity

Decreased in

    Noncompliance with therapeutic regimen

Critical findings

  • Note: The adverse effects of subtherapeutic levels are also important. Care should be taken to investigate signs and symptoms of too little and too much medication. Note and immediately report to the requesting HCP any critically increased or subtherapeutic values and related symptoms.

  • It is essential that a critical finding be communicated immediately to the requesting HCP. A listing of these findings varies among facilities.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. The notification processes will vary among facilities. Upon receipt of the critical finding the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical finding, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

  • Acetaminophen: Greater Than 200 mcg/mL (4 hr postingestion): (SI Greater Than 1,324 micromol/L [4 hr postingestion])

  • Signs and symptoms of acetaminophen intoxication occur in stages over a period of time. In stage I (0 to 24 hr after ingestion), symptoms may include gastrointestinal irritation, pallor, lethargy, diaphoresis, metabolic acidosis, and possibly coma. In stage II (24 to 48 hr after ingestion), signs and symptoms may include right upper quadrant abdominal pain; elevated liver enzymes, aspartate aminotransferase (AST), and alanine aminotransferase (ALT); and possible decreased renal function. In stage III (72 to 96 hr after ingestion), signs and symptoms may include nausea, vomiting, jaundice, confusion, coagulation disorders, continued elevation of AST and ALT, decreased renal function, and coma. Intervention may include gastrointestinal decontamination (stomach pumping) if the patient presents within 6 hr of ingestion or administration of N-acetylcysteine (Mucomyst) in the case of an acute intoxication in which the patient presents more than 6 hr after ingestion.

  • ASA: Greater Than 40 mg/dL: (SI Greater Than 2.9 mmol/L)

  • Signs and symptoms of salicylate intoxication include ketosis, convulsions, dizziness, nausea, vomiting, hyperactivity, hyperglycemia, hyperpnea, hyperthermia, respiratory arrest, and tinnitus. Possible interventions include administration of activated charcoal as vomiting ceases, alkalinization of the urine with bicarbonate, and a single dose of vitamin K (for rare instances of hypoprothrombinemia).

Interfering factors

  • Blood drawn in serum separator tubes (gel tubes).
  • Drugs that may increase acetaminophen levels include diflunisal, metoclopramide, and probenecid.
  • Drugs that may decrease acetaminophen levels include carbamazepine, cholestyramine, iron, oral contraceptives, and propantheline.
  • Drugs that increase ASA levels include choline magnesium trisalicylate, cimetidine, furosemide, and sulfinpyrazone.
  • Drugs and substances that decrease ASA levels include activated charcoal, antacids (aluminum hydroxide), corticosteroids, and iron.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist with evaluation of how much medication is in his or her system.
  • Obtain a complete history of the time and amount of drug ingested by the patient.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Review results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a history of the patient’s genitourinary and hepatobiliary systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures. These medications are metabolized and excreted by the kidneys and liver.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications:
  • Lack of consideration for the proper collection time relative to the dosing schedule can provide misleading information that may result in erroneous interpretation of levels, creating the potential for a medication error–related injury to the patient.

  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Consider recommended collection time in relation to the dosing schedule. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection, noting the last dose of medication taken. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop the bleeding. Observe/assess the venipuncture site for bleeding and hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Nutritional Considerations: Include avoidance of alcohol consumption.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Explain to the patient the importance of following the medication regimen and instructions regarding food and drug interactions. Answer any questions or address any concerns voiced by the patient or family.
  • Recognize anxiety related to test results, and explain to the patient the importance of following the medication regimen and instructions regarding food and drug interactions. Instruct the patient to be prepared to provide the pharmacist with a list of other medications he or she is already taking in the event that the requesting HCP prescribes a medication.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include ALT, AST, bilirubin, biopsy liver, BUN, creatinine, electrolytes, glucose, lactic acid, aPTT, and PT/INR.
  • See the Genitourinary and Hepatobiliary systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners