Acetaminophen 500mg X/s Tablets
WARNING: Liver problems have happened with the use of acetaminophen. Sometimes, this has led to a liver transplant or death. Most of the time, liver problems happened in people taking more than 4,000 mg (milligrams) of acetaminophen in a day. People were also often taking more than 1 drug that had acetaminophen in it. If you have questions, talk with your doctor. @ COMMON USES: It is used to ease pain and fever.
Drug Class
Analgesic, Antipyretic
Pharmacologic Class
Para-aminophenol derivative
Pregnancy Category
Category B (old system); generally considered safe for use during pregnancy when used as directed. New system advises risk/benefit assessment.
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Acetaminophen is a common over-the-counter medicine used to relieve pain (like headaches, muscle aches, and menstrual cramps) and reduce fever. It works by affecting how your brain senses pain and by cooling down your body.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. You can take this medication with or without food.
Storing and Disposing of Your Medication
Keep your medication at room temperature, away from light, and in a dry place. Store it in its original container with the lid tightly closed. Do not refrigerate or freeze your medication, and avoid storing it in a bathroom.
Missing a Dose
If you take this medication regularly and miss a dose, take it as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your normal schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, follow your doctor's instructions and do not take it more frequently than recommended.
To use this medication correctly, follow your doctor's instructions and read all the information provided. You can take this medication with or without food.
Storing and Disposing of Your Medication
Keep your medication at room temperature, away from light, and in a dry place. Store it in its original container with the lid tightly closed. Do not refrigerate or freeze your medication, and avoid storing it in a bathroom.
Missing a Dose
If you take this medication regularly and miss a dose, take it as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your normal schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, follow your doctor's instructions and do not take it more frequently than recommended.
Lifestyle & Tips
- Do not take more than the recommended dose, as this can cause serious liver damage.
- Be aware of other medications you are taking that may also contain acetaminophen (e.g., cold and flu remedies, prescription pain relievers) to avoid accidental overdose.
- Limit or avoid alcohol consumption while taking acetaminophen, especially if you take it regularly, as alcohol increases the risk of liver damage.
- If your pain or fever worsens or lasts more than a few days, consult a doctor.
Available Forms & Alternatives
Available Strengths:
- Acetaminophen 120mg Suppositories
- Acetaminophen 650mg Suppositories
- Acetaminophen 500mg Tablets
- Acetaminophen Child 160mg/5ml Susp
- Acetaminophen 500mg X/s Tablets
- Acetaminophen 500mg E/s Caplets
- Acetaminophen 160mg/5ml Solution
- Acetaminophen 325mg Tablets
- Acetaminophen 10mg/ml Inj, 100ml
- Acetaminophen 160mg/5ml Liquid
- Acetaminophen 500mg E/s Tablets
- Acetaminophen Child 160mg/5ml Susp
- Acetaminophen Infant 160mg/5ml Susp
- Acetaminophen 650mg ER Tablets
Dosing & Administration
Adult Dosing
Standard Dose:
500 mg to 1000 mg (two 500mg tablets) every 4 to 6 hours as needed
Dose Range:
500 - 1000 mg
Condition-Specific Dosing:
Maximum Daily Dose:
Do not exceed 4000 mg (4g) in 24 hours. Some sources recommend a lower maximum of 3000 mg (3g) for chronic use or in patients with risk factors for hepatotoxicity.
Pediatric Dosing
Neonatal:
Not established (use only under medical supervision)
Infant:
Not established (use only under medical supervision, typically liquid formulations are used for infants and children based on weight)
Child:
Not established for 500mg tablets (dosing is weight-based, typically 10-15 mg/kg per dose every 4-6 hours, not to exceed 5 doses in 24 hours. 500mg tablets are generally not recommended for children under 12 years old due to high dose per tablet).
Adolescent:
12 years and older: 500 mg to 1000 mg every 4 to 6 hours as needed, not to exceed 4000 mg in 24 hours.
Dose Adjustments
Renal Impairment:
Mild:
No adjustment typically needed.
Moderate:
No adjustment typically needed.
Severe:
Consider increasing dosing interval to every 6-8 hours. Avoid chronic use or high doses. (CrCl < 30 mL/min)
Dialysis:
Acetaminophen is dialyzable. Supplemental dose may be needed after dialysis, but generally, standard dosing with extended intervals (e.g., every 6-8 hours) is sufficient.
Hepatic Impairment:
Mild:
Use with caution; consider lower doses or extended intervals.
Moderate:
Use with extreme caution; significant dose reduction or avoidance may be necessary. Consult physician.
Severe:
Contraindicated or use with extreme caution and under strict medical supervision due to increased risk of hepatotoxicity.
Pharmacology
Mechanism of Action
Acetaminophen (paracetamol) is thought to produce analgesia by inhibiting prostaglandin synthesis primarily in the central nervous system (CNS) and to a lesser extent peripherally. It is also believed to act on descending serotonergic pathways and to modulate the endocannabinoid system. Its antipyretic effect is due to direct action on the hypothalamic heat-regulating center, leading to peripheral vasodilation, increased blood flow, and sweating, resulting in heat loss.
Pharmacokinetics
Absorption:
Bioavailability:
60-90% (oral)
Tmax:
0.5-2 hours (oral)
FoodEffect:
Food may delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
Approximately 0.9 L/kg
ProteinBinding:
10-25% (at therapeutic concentrations)
CnssPenetration:
Yes (readily crosses the blood-brain barrier)
Elimination:
HalfLife:
1.25-3 hours (in adults with normal hepatic function)
Clearance:
Approximately 5 mL/min/kg
ExcretionRoute:
Renal (90-100% excreted in urine as glucuronide and sulfate conjugates, and a small amount of unchanged drug)
Unchanged:
Less than 5%
Pharmacodynamics
OnsetOfAction:
30-60 minutes
PeakEffect:
1-2 hours
DurationOfAction:
4-6 hours
Safety & Warnings
BLACK BOX WARNING
Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant or death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 mg per day, and often involve more than one acetaminophen-containing product. Severe skin reactions, such as Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Acute Generalized Exanthematous Pustulosis (AGEP), have been reported rarely in patients taking acetaminophen. Discontinue acetaminophen at the first appearance of skin rash or any other sign of hypersensitivity and seek medical attention.
Side Effects
Urgent Side Effects: Seek Medical Help Immediately
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Difficulty urinating or changes in urine output
Severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), characterized by:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Upset stomach or vomiting
Trouble sleeping
Headache
Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Difficulty urinating or changes in urine output
Severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis), characterized by:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in the mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Upset stomach or vomiting
Trouble sleeping
Headache
Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Yellowing of skin or eyes (jaundice)
- Dark urine
- Pale stools
- Persistent nausea or vomiting
- Upper right abdominal pain
- Unusual tiredness or weakness
- Skin rash, hives, or itching
- Swelling of the face, lips, tongue, or throat
- Difficulty breathing or swallowing
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you have liver disease, as this may affect the use of this medication.
This list is not exhaustive, and it is crucial to discuss all your medications (including prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist. They will help determine if it is safe to take this medication in conjunction with your other medications and health issues.
Remember, do not start, stop, or adjust the dosage of any medication without first consulting your doctor to ensure your safety.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you have liver disease, as this may affect the use of this medication.
This list is not exhaustive, and it is crucial to discuss all your medications (including prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist. They will help determine if it is safe to take this medication in conjunction with your other medications and health issues.
Remember, do not start, stop, or adjust the dosage of any medication without first consulting your doctor to ensure your safety.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
When taking this drug, be cautious not to take other products that contain acetaminophen, as this can lead to excessive intake. Carefully check the labels of all medications and supplements to avoid accidental overdose. Taking too much acetaminophen can cause liver damage.
To ensure safe use, follow the dosage instructions precisely. Do not exceed the recommended daily dose of acetaminophen. If you are unsure about the maximum daily dose, consult your doctor or pharmacist. While some individuals may be advised to take up to 4,000 mg per day under medical guidance, others, such as those with liver problems or children, may require lower doses. If you suspect you have taken too much acetaminophen in a day, contact your doctor immediately, even if you feel well.
Before consuming alcohol, discuss the potential risks with your doctor. Additionally, this medication may interfere with certain laboratory tests, so it is crucial to inform all healthcare providers and laboratory personnel that you are taking this drug.
When administering this medication to children, note that different brands may have varying dosage recommendations. Always consult with your doctor before giving this medication to a child.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. It is necessary to discuss the potential benefits and risks of this medication to both you and your baby.
When taking this drug, be cautious not to take other products that contain acetaminophen, as this can lead to excessive intake. Carefully check the labels of all medications and supplements to avoid accidental overdose. Taking too much acetaminophen can cause liver damage.
To ensure safe use, follow the dosage instructions precisely. Do not exceed the recommended daily dose of acetaminophen. If you are unsure about the maximum daily dose, consult your doctor or pharmacist. While some individuals may be advised to take up to 4,000 mg per day under medical guidance, others, such as those with liver problems or children, may require lower doses. If you suspect you have taken too much acetaminophen in a day, contact your doctor immediately, even if you feel well.
Before consuming alcohol, discuss the potential risks with your doctor. Additionally, this medication may interfere with certain laboratory tests, so it is crucial to inform all healthcare providers and laboratory personnel that you are taking this drug.
When administering this medication to children, note that different brands may have varying dosage recommendations. Always consult with your doctor before giving this medication to a child.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. It is necessary to discuss the potential benefits and risks of this medication to both you and your baby.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Abdominal pain (especially upper right quadrant)
- Sweating
- Loss of appetite
- Extreme tiredness
- Confusion
- Later signs (24-48 hours post-ingestion): signs of liver failure (jaundice, dark urine, easy bruising/bleeding, encephalopathy)
What to Do:
If you suspect an overdose, seek immediate medical attention. Call 911 or your local poison control center (e.g., 1-800-222-1222 in the US) right away, even if you feel well. Treatment may include activated charcoal if caught early, and the antidote N-acetylcysteine (NAC).
Drug Interactions
Contraindicated Interactions
- Severe hepatic impairment (relative contraindication)
Major Interactions
- Alcohol (chronic heavy use increases risk of hepatotoxicity)
- Warfarin (may increase INR and bleeding risk with chronic high-dose acetaminophen use)
- Isoniazid (increased risk of hepatotoxicity)
- Phenytoin, Carbamazepine, Phenobarbital, Rifampin (CYP inducers, may increase formation of toxic NAPQI metabolite, increasing hepatotoxicity risk)
Moderate Interactions
- Cholestyramine (reduces acetaminophen absorption if given concurrently or shortly after)
- Lamotrigine (may reduce lamotrigine serum concentrations)
- Zidovudine (may increase zidovudine toxicity due to competition for glucuronidation)
Minor Interactions
- Oral contraceptives (may slightly increase acetaminophen clearance)
Monitoring
Baseline Monitoring
Liver function tests (ALT, AST, bilirubin)
Rationale: To establish baseline in patients with pre-existing liver disease or risk factors for hepatotoxicity (e.g., chronic alcohol use, malnutrition).
Timing: Prior to initiating chronic high-dose therapy or in at-risk patients.
Routine Monitoring
Liver function tests (ALT, AST)
Frequency: Periodically, especially with chronic high-dose use or in patients with risk factors for hepatotoxicity.
Target: Within normal limits
Action Threshold: Elevations > 3 times upper limit of normal (ULN) or any significant elevation with symptoms of liver injury warrant discontinuation and further evaluation.
Symptom Monitoring
- Signs of liver damage (e.g., yellowing of skin/eyes, dark urine, persistent nausea/vomiting, abdominal pain, unusual tiredness)
- Signs of allergic reaction (e.g., rash, itching, swelling, severe dizziness, trouble breathing)
- Symptoms of overdose (e.g., nausea, vomiting, abdominal pain, sweating, confusion, extreme tiredness)
Special Patient Groups
Pregnancy
Acetaminophen is generally considered the analgesic and antipyretic of choice during pregnancy when used at recommended doses for short durations. However, recent studies suggest potential associations with neurodevelopmental outcomes with prolonged or high-dose use, prompting caution and advising use at the lowest effective dose for the shortest duration necessary.
Trimester-Specific Risks:
First Trimester:
Generally considered low risk for congenital malformations.
Second Trimester:
Generally considered low risk.
Third Trimester:
Generally considered low risk, but some studies suggest potential associations with asthma or neurodevelopmental issues with chronic exposure.
Lactation
Acetaminophen is considered compatible with breastfeeding. It is excreted into breast milk in small amounts, which are generally not considered harmful to the infant.
Infant Risk:
Low risk. Monitor infant for any unusual side effects, though unlikely.
Pediatric Use
Dosing must be strictly weight-based for children under 12 years old. 500mg tablets are generally not suitable for young children due to the high dose. Always use appropriate pediatric formulations (liquid, chewable) and dosing devices. Avoid exceeding recommended daily limits.
Geriatric Use
Generally safe for use in the elderly at recommended doses. However, elderly patients may have reduced hepatic or renal function, increasing the risk of adverse effects. Monitor for signs of liver toxicity, especially if comorbidities or polypharmacy are present. Lower maximum daily doses (e.g., 3000 mg) may be considered in frail or at-risk elderly patients.
Clinical Information
Clinical Pearls
- Acetaminophen is often found in combination products (e.g., cold/flu medications, opioid analgesics). Always check labels to avoid accidental overdose.
- The maximum daily dose of 4000 mg (4g) should be strictly adhered to. For patients with chronic alcohol use, liver disease, or malnutrition, a lower maximum daily dose (e.g., 2000-3000 mg) is often recommended.
- N-acetylcysteine (NAC) is the antidote for acetaminophen overdose and is most effective when administered within 8-10 hours of ingestion.
- Patients should be educated on the signs and symptoms of liver toxicity and instructed to seek immediate medical attention if they occur.
Alternative Therapies
- Nonsteroidal Anti-inflammatory Drugs (NSAIDs) such as Ibuprofen, Naproxen, Aspirin (for pain and fever)
- Topical analgesics (e.g., lidocaine patches, capsaicin cream)
- Non-pharmacological pain management (e.g., heat/cold therapy, physical therapy, massage, acupuncture)
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets (generic 500mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 (preferred generic) for prescription, widely available OTC.
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it occurred.