Acetaminophen 325mg 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
Not applicable (Risk Summary)
FDA Approved
Sep 1951
DEA Schedule
Not Controlled
Overview
What is this medicine?
Acetaminophen is a common medicine used to relieve pain and reduce fever. It works by affecting how your brain senses pain and controls body temperature. It's important to use it exactly as directed to avoid serious side effects, especially liver damage.
How to Use This Medicine
Taking Your Medication
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided to you and follow the instructions closely. You can take this medication with or without food.
Storing and Disposing of Your Medication
To keep your medication effective, store it at room temperature (do not refrigerate or freeze). Keep it in its original container, protected from light, with the lid tightly closed. Store it in a dry place, avoiding the 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 return to your normal schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, do not take it more frequently than directed by your doctor.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided to you and follow the instructions closely. You can take this medication with or without food.
Storing and Disposing of Your Medication
To keep your medication effective, store it at room temperature (do not refrigerate or freeze). Keep it in its original container, protected from light, with the lid tightly closed. Store it in a dry place, avoiding the 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 return to your normal schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, do not take it more frequently than directed by your doctor.
Lifestyle & Tips
- Do not take more than the recommended dose.
- Do not take with other medicines that contain acetaminophen (check labels of cold, flu, and pain medicines).
- Limit or avoid alcohol consumption while taking acetaminophen, especially if you drink 3 or more alcoholic drinks per day.
- Stay hydrated.
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:
650 mg (two 325mg tablets) orally every 4 to 6 hours as needed
Dose Range:
325 - 1000 mg
Condition-Specific Dosing:
Maximum daily dose:
4000 mg in 24 hours (some sources recommend 3000 mg for chronic use or in patients with risk factors for hepatotoxicity)
Pediatric Dosing
Neonatal:
Not established (use caution, consult physician)
Infant:
10-15 mg/kg/dose orally every 4-6 hours as needed, not to exceed 5 doses in 24 hours
Child:
10-15 mg/kg/dose orally every 4-6 hours as needed, not to exceed 5 doses in 24 hours (max 75 mg/kg/day, not to exceed 4000 mg/day)
Adolescent:
10-15 mg/kg/dose orally every 4-6 hours as needed, not to exceed 5 doses in 24 hours (max 75 mg/kg/day, not to exceed 4000 mg/day)
Dose Adjustments
Renal Impairment:
Mild:
No adjustment typically needed
Moderate:
Consider increasing dosing interval to every 6 hours
Severe:
Consider increasing dosing interval to every 8 hours (CrCl < 30 mL/min)
Dialysis:
Acetaminophen is dialyzable; supplemental dose may be needed after hemodialysis. Consult specific guidelines.
Hepatic Impairment:
Mild:
Use with caution, consider reduced dose or extended interval
Moderate:
Use with extreme caution, reduced dose and extended interval (e.g., 75% of usual dose, max 2000 mg/day)
Severe:
Contraindicated or avoid use due to risk of hepatotoxicity
Pharmacology
Mechanism of Action
Acetaminophen's exact mechanism is not fully understood but is believed to involve central inhibition of prostaglandin synthesis, primarily through inhibition of cyclooxygenase (COX) enzymes in the central nervous system (CNS), particularly COX-3. It also may involve activation of descending serotonergic pathways and interaction with the endocannabinoid system. Unlike NSAIDs, it has minimal peripheral anti-inflammatory effects.
Pharmacokinetics
Absorption:
Bioavailability:
60-90%
Tmax:
0.5-2 hours (oral)
FoodEffect:
Food may delay Tmax but does not significantly affect the extent of absorption.
Distribution:
Vd:
0.9 L/kg
ProteinBinding:
10-25% (at therapeutic concentrations)
CnssPenetration:
Limited (sufficient for central effects)
Elimination:
HalfLife:
1.5-3 hours (adults); 2-5 hours (neonates)
Clearance:
Not available (primarily hepatic metabolism and renal excretion)
ExcretionRoute:
Renal (90-100% as metabolites)
Unchanged:
< 5%
Pharmacodynamics
OnsetOfAction:
30-60 minutes
PeakEffect:
1-2 hours
DurationOfAction:
4-6 hours
Confidence:
Medium
Safety & Warnings
BLACK BOX WARNING
Risk of severe liver damage: Acetaminophen can cause severe liver damage if you take more than 4,000 mg in 24 hours, or if you take it with other acetaminophen-containing products, or if you drink 3 or more alcoholic drinks every day while using this product. Risk of severe allergic reactions: Acetaminophen can cause severe skin reactions such as Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Acute Generalized Exanthematous Pustulosis (AGEP), which can be fatal. Stop use and seek medical help right away if you have a skin rash or other allergic reaction.
Side Effects
Urgent Side Effects: Seek Medical Help Immediately
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice 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
Some allergic reactions can be life-threatening, so prompt medical attention is crucial.
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Urination problems, such as:
+ Inability to pass urine
+ Changes in urine output
A severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may occur, which can cause severe health problems and potentially be fatal. Seek medical help immediately if you experience:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in your mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or only minor ones. However, if you notice any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Upset stomach or vomiting
Trouble sleeping
Headache
* Constipation
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, consult 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, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice 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
Some allergic reactions can be life-threatening, so prompt medical attention is crucial.
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Urination problems, such as:
+ Inability to pass urine
+ Changes in urine output
A severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may occur, which can cause severe health problems and potentially be fatal. Seek medical help immediately if you experience:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in your mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or only minor ones. However, if you notice any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Upset stomach or vomiting
Trouble sleeping
Headache
* Constipation
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, consult 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
- Clay-colored stools
- Persistent nausea or vomiting
- Loss of appetite
- Unusual tiredness or weakness
- Pain in the upper right side of the abdomen
- Rash, hives, itching, or swelling (especially of the face, 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 your ability to take this medication.
This list is not exhaustive, and it is crucial to discuss all your medications, health conditions, and concerns with your doctor. This includes:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
* Any health problems you have, as they may interact with this medication
To ensure your safety, always check with your doctor before starting, stopping, or changing the dose of any medication. This will help prevent potential interactions and ensure that it is safe for you to take this medication with your other drugs and health conditions.
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 your ability to take this medication.
This list is not exhaustive, and it is crucial to discuss all your medications, health conditions, and concerns with your doctor. This includes:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
* Any health problems you have, as they may interact with this medication
To ensure your safety, always check with your doctor before starting, stopping, or changing the dose of any medication. This will help prevent potential interactions and ensure that it is safe for you to take this medication with your other drugs and health conditions.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
To avoid potential liver problems, be cautious not to take other products that contain acetaminophen. Carefully check the labels of any medications or supplements you are taking. Taking too much acetaminophen can cause liver damage.
Follow the dosage instructions precisely, and do not exceed the recommended daily amount of acetaminophen. If you are unsure about the maximum daily dose, consult your doctor or pharmacist. While some individuals may be advised by their doctor to take up to 4,000 milligrams (mg) of acetaminophen per day, 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 your 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. Consult your doctor before giving this medication to a child to ensure the correct dose.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. You and your doctor will need to discuss the potential benefits and risks of taking this medication to make an informed decision about its use.
To avoid potential liver problems, be cautious not to take other products that contain acetaminophen. Carefully check the labels of any medications or supplements you are taking. Taking too much acetaminophen can cause liver damage.
Follow the dosage instructions precisely, and do not exceed the recommended daily amount of acetaminophen. If you are unsure about the maximum daily dose, consult your doctor or pharmacist. While some individuals may be advised by their doctor to take up to 4,000 milligrams (mg) of acetaminophen per day, 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 your 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. Consult your doctor before giving this medication to a child to ensure the correct dose.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. You and your doctor will need to discuss the potential benefits and risks of taking this medication to make an informed decision about its use.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Loss of appetite
- Sweating
- Stomach pain
- Extreme tiredness
- Yellowing of the skin or eyes (jaundice)
- Dark urine
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Overdose can cause severe, irreversible liver damage and death. N-acetylcysteine (NAC) is the antidote and is most effective when given within 8 hours of overdose.
Drug Interactions
Major Interactions
- Alcohol (chronic heavy use - increased risk of hepatotoxicity)
- Isoniazid (increased risk of hepatotoxicity)
- Warfarin (increased INR and bleeding risk with chronic high-dose acetaminophen)
Moderate Interactions
- Carbamazepine (increased risk of hepatotoxicity)
- Phenytoin (increased risk of hepatotoxicity)
- Phenobarbital (increased risk of hepatotoxicity)
- Rifampin (increased risk of hepatotoxicity)
- Lamotrigine (decreased lamotrigine levels)
- Cholestyramine (decreased acetaminophen absorption if given concurrently)
Minor Interactions
- Oral contraceptives (may slightly decrease acetaminophen clearance)
Monitoring
Baseline Monitoring
Liver function tests (ALT, AST, bilirubin)
Rationale: To assess baseline hepatic function, especially 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 (e.g., every 6-12 months) for patients on chronic high-dose therapy or with risk factors for hepatotoxicity.
Target: Within normal limits
Action Threshold: Significant elevation (e.g., >3x upper limit of normal) warrants dose reduction or discontinuation and further investigation.
INR (International Normalized Ratio)
Frequency: More frequently (e.g., weekly) when initiating or changing acetaminophen dose in patients on warfarin.
Target: Individualized therapeutic range for warfarin
Action Threshold: INR outside target range requires warfarin dose adjustment.
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)
- Signs of gastrointestinal bleeding (rare, but possible with chronic high doses, especially in combination with NSAIDs)
Special Patient Groups
Pregnancy
Generally considered the analgesic/antipyretic of choice during pregnancy when medically indicated, at the lowest effective dose for the shortest duration. However, recent studies suggest potential associations with neurodevelopmental outcomes, warranting cautious use and further research.
Trimester-Specific Risks:
First Trimester:
Generally considered low risk, but use only if clearly needed.
Second Trimester:
Generally considered low risk.
Third Trimester:
Generally considered low risk, but use only if clearly needed.
Lactation
Considered compatible with breastfeeding. Acetaminophen is excreted into breast milk in small amounts, but adverse effects on breastfed infants are not expected at therapeutic doses.
Infant Risk:
Low risk (L1)
Pediatric Use
Widely used and generally safe when dosed appropriately by weight. Strict adherence to weight-based dosing and maximum daily limits is crucial to prevent overdose. Use appropriate formulations (e.g., liquid for infants/young children).
Geriatric Use
No specific dose adjustment is typically needed based on age alone, but elderly patients may have reduced hepatic or renal function, increasing the risk of adverse effects. Monitor for signs of hepatotoxicity and adjust dose/interval if renal or hepatic impairment is present. Polypharmacy increases the risk of accidental overdose from multiple acetaminophen-containing products.
Clinical Information
Clinical Pearls
- Always check labels of other medications (e.g., cold/flu remedies, combination pain relievers) to avoid accidental acetaminophen overdose.
- The maximum daily dose is 4000 mg, but many clinicians recommend a lower maximum (e.g., 3000 mg) for chronic use or in patients with risk factors for liver damage.
- N-acetylcysteine (NAC) is the antidote for acetaminophen overdose and is most effective when administered within 8 hours of ingestion.
- Acetaminophen is not an anti-inflammatory drug; for inflammatory pain, NSAIDs may be more appropriate if not contraindicated.
- Educate patients on the signs and symptoms of liver damage and the importance of seeking immediate medical attention for suspected overdose.
Alternative Therapies
- Nonsteroidal Anti-inflammatory Drugs (NSAIDs) such as Ibuprofen, Naproxen (for pain and fever, with anti-inflammatory effects)
- Aspirin (for pain and fever, but not recommended for children/adolescents with viral infections due to Reye's syndrome risk)
- Non-pharmacological pain relief (e.g., rest, ice/heat, massage, physical therapy)
Cost & Coverage
Average Cost:
$5 - $20 per 100 tablets (generic)
Generic Available:
Yes
Insurance Coverage:
Tier 1 (Preferred Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to check with your pharmacist. If you have any questions or concerns about this medication, do not hesitate to discuss them with 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 detailed information about the overdose, including the medication taken, the amount, and the time it occurred.