Par

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Par

Quick Facts

Property Description
Active ingredient Acetaminophen (Paracetamol)
Pharmacological class Analgesic and Antipyretic
Common purpose Relief of mild-to-moderate pain and fever
Origin Synthetic compound
Typical forms Tablet, Oral Suspension, Suppository

What is Par: Defining the Medicine and its Chemical Name

Par is the medicine containing the active substance Acetaminophen, which is globally recognized as Paracetamol. This compound is a synthetic compound derived from the Para-aminophenol group and is primarily prepared as a Single-ingredient product for targeted relief. The chemical identity of the active substance is N-(4-hydroxyphenyl)acetamide. It is recognized as an essential non-opioid analgesic for clinical use.

Pharmacological Class and General Purpose

Par is formally categorized as both an Analgesic (a substance that relieves pain) and an Antipyretic (a substance that reduces fever). Its primary purpose is to provide effective symptomatic relief from general aches and elevated body temperature. This medication is considered a cornerstone treatment for acute pain and fever globally. Unlike most Nonsteroidal Anti-inflammatory Drugs (NSAIDs), its therapeutic value focuses squarely on pain and temperature control with minimal peripheral anti-inflammatory effects, differentiating its action profile.

Available Forms and Preparation Type

The medicine is manufactured in various dosage forms to facilitate suitable systemic administration across different patient needs. The most common forms include the standard tablet, liquid oral suspension often used for pediatric patients, the rectal suppository, and the sterile intravenous solution used in clinical settings. This spectrum of preparations ensures versatility in the route of administration—Oral, Rectal, and Intravenous—allowing for appropriate delivery under diverse clinical circumstances.

Regulatory References

  1. National Library of Medicine
  2. WHO Essential Medicines List
  3. NIH MedlinePlus

What side effects are possible with Par?

Possible side effects and safety information

Official regulatory documents organize the safety profile of Par based on the severity and frequency of documented adverse reactions, as well as specific restrictions on use.

Safety Restrictions and Contraindications

Par is contraindicated (should not be used) in individuals with a personal or family history of Medullary Thyroid Carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Use is also contraindicated in patients who have experienced a previous severe hypersensitivity reaction to the medicine. The medicine is not recommended for use during pregnancy.

Most Common Adverse Reactions

The most frequently reported side effects, especially during the initial dose-increase period, primarily affect the gastrointestinal system. These reactions are officially classified by frequency:

Classification Adverse Reaction
Very Common (geq10%) Nausea, Diarrhea
Common (geq1%- <10%) Vomiting, Abdominal pain, Constipation, Headache, Decreased Appetite, Hypoglycemia (when co-administered with certain other medicines)

Serious and Clinically Significant Risks

The regulatory profile highlights several serious risks across different body systems that require caution:

  • Pancreatitis: Acute inflammation of the pancreas has been reported.
  • Thyroid C-cell Tumors: The drug carries a Boxed Warning based on the finding of C-cell tumors in animal studies (human relevance is undetermined).
  • Gallbladder Disease: Acute gallbladder events, including cholelithiasis (gallstones), have been documented.
  • Acute Kidney Injury: This risk is often secondary to dehydration caused by severe gastrointestinal adverse reactions (vomiting/diarrhea).
  • Diabetic Retinopathy: Complications of pre-existing diabetic retinopathy may occur, particularly in patients with Type 2 Diabetes.

Overdose and Emergency Response

Overdose and When to Seek Help: Official Regulatory Information

The official overdose profile for Par (Acetaminophen/Paracetamol) is defined by the high risk of severe, delayed organ damage, requiring mandatory, urgent medical action regardless of the patient's condition. Regulatory bodies stress that the most serious outcomes are often delayed.

Immediate Mandatory Action

Action Required Official Statement Summary
Help Seeking Seek immediate medical attention or contact a Poison Help center urgently, even if the patient feels well.
Treatment Immediate treatment is essential. Urgent hospital referral is required.

Documented Overdose Manifestations

Initial symptoms (within 24 hours) may be mild or absent, including Nausea, Vomiting, Pallor, and Abdominal Pain. The most severe documented outcomes are Severe Liver Damage (Hepatotoxicity), Acute Liver Failure (ALF), and Death, which can be preceded by signs like Jaundice, Metabolic Acidosis, and elevated liver function tests (e.g., AST/ALT).

Antidote and Risk Factors

The specific antidote is N-acetylcysteine (NAC), which must be administered urgently, with its maximum protective effect seen within 8 hours post-ingestion. Hospital monitoring of hepatic and renal function is required. Risk factors for increased severity include Chronic Alcoholism, Chronic Malnutrition, Dehydration, and pre-existing Liver Impairment.

Therapeutic Uses of Par

What Par Treats: Main Uses and Benefits

Relief for Mild-to-Moderate Pain and Aches

Paracetamol is commonly used to address mild-to-moderate pain across various situations. This domain covers the analgesic effect of the medication, aiming to ease the intensity of discomfort from headaches, muscle pain, backache, toothache, and menstrual cramps. Applying Par provides supportive relief that contributes to easing the overall symptom load and supports general well-being during symptomatic phases. It is commonly used in settings requiring additional management of discomfort, relevant in contexts involving acute symptomatic episodes.

Reduction of Fever and Systemic Symptoms

This medication is applied across domains where additional symptomatic support is needed to address symptoms related to systemic imbalance, such as fever. It is commonly used when symptoms cluster into patterns requiring supportive management, such as the fever and aches associated with the common cold and influenza (flu). The key therapeutic benefit is assisting with symptomatic relief of high temperature, which may help patients cope more steadily with symptoms associated with acute or episodic changes.

Symptomatic Support Across Patient Groups

This cluster highlights the medication's broad applicability for short-term symptomatic assistance across diverse demographics. Par is generally applicable in conditions requiring supportive relief for adults and children, and specific patient groups like pregnant or breastfeeding women (under medical guidance). It offers symptomatic relief that may help patients cope more steadily when acute symptoms become more noticeable across diverse ages, contributing to easing the overall symptom load during periods of heightened symptoms.


Quick Fact: Relief for Pain and Fever

Property Description
Primary Domain Symptomatic relief (Analgesia and Antipyresis)
Symptom Intensity Mild-to-moderate discomfort and fever
Typical Use Context Acute, episodic, and seasonal illness manifestations
Core Patient Benefit Supports maintenance of functional stability by easing symptom load

Regulatory References

  1. NIH MedlinePlus Drug Information

Eligibility and Restrictions for Use

Eligibility Map: Who Can and Cannot Use Paracetamol (Acetaminophen)

The medicine is contraindicated and must not be used by patients with severe active liver disease or known hypersensitivity to Acetaminophen or any component of the formulation. These are non-negotiable exclusions defined in regulatory labeling.

Age-Related Eligibility

Paracetamol is permitted for use across the entire age spectrum, including adults, adolescents, children, and neonates. However, pediatric use is conditional, requiring adherence to age- and weight-specific guidelines in the official product information.

Condition-Specific Restrictions

Use requires caution or restriction in populations with underlying health issues. This includes patients with severe renal impairment, non-severe hepatic impairment, chronic alcoholism, severe malnutrition, or G6PD deficiency. These populations may be at higher risk and their use is conditionally addressed in regulatory documents.

Pregnancy and Lactation Status

Paracetamol is the recommended first-choice painkiller for use during pregnancy when clinically necessary, used at the lowest effective dose for the shortest duration. It is also considered acceptable and compatible with breastfeeding by regulatory authorities.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The interaction profile of Par (Acetaminophen/Paracetamol) is defined by documented risks of additive toxicity and altered drug exposure, as stated in regulatory prescribing information.

Documented Interaction Patterns

Category Officially Documented Outcomes
Contraindicated Combinations Co-administration with other products containing Paracetamol is officially restricted due to significant risk of acute liver damage and overdose.
Pharmacodynamic Interactions Prolonged, regular use with oral anticoagulants (e.g., Warfarin) is documented to enhance the anticoagulant effect, which increases the risk of bleeding.
Metabolic Risk Factors Substances that induce liver enzymes (e.g., Carbamazepine, Rifampicin, St. John's Wort) may increase the hepatotoxic potential of Paracetamol. The hazard of toxicity is also increased by chronic ingestion of 3 or more alcoholic drinks per day.
Exposure-Altering Interactions Metoclopramide and Domperidone increase the speed of Paracetamol absorption. In contrast, Cholestyramine significantly reduces Paracetamol absorption and requires administration to be separated by at least one hour to avoid this reduction.
Clearance Alterations Probenecid affects Paracetamol excretion and may alter plasma concentrations. Paracetamol may also increase the concentration of Chloramphenicol by reducing its hepatic metabolism.

Use is often contraindicated in patients with severe active liver disease due to the heightened risk of adverse outcomes from these interactions.

Mechanism of Action

The mechanism of action for Acetaminophen (Paracetamol) is defined by its selective influence on central regulatory systems, involving the modulation of central prostaglandin signaling and the potentiation of descending inhibitory nociceptive pathways.

Regulation of the Central Thermoregulatory Center

This domain involves the drug’s primary action as a weak inhibitor of Cyclooxygenase (COX) enzymes specifically within the Central Nervous System (CNS), particularly in the hypothalamus. By limiting the synthesis of Prostaglandin E2 (PGE2) in this region, the mechanism adjusts the hypothalamic set-point for temperature control, initiating physiological heat-loss responses such as peripheral vasodilation and sweating.

Metabolite Modulation of Descending Nociceptive Pathways

The drug's central analgesic mechanism is contingent on its metabolism into the active compound AM404, which then interacts with key nociceptive signaling receptors like TRPV1 and CB1 in the brain and spinal cord. This specific molecular modulation potentiates the descending inhibitory serotonergic pathway, which is the nervous system's intrinsic pathway for modulating nociceptive signal transmission.

Dosage and Administration Information

Paracetamol (Par) is administered systemically via three pathways: oral, rectal, and intravenous (IV) infusion, with the choice of route depending on clinical needs and available formulation. Use is governed by dose limits and timing intervals to ensure appropriate application, regardless of the administration method chosen.

Administration Guidelines and Dosage

For adults weighing 50 kg or more, the standard immediate-release oral dose is generally between 325 mg and 1000 mg. This dose is administered as needed, observing a minimum dosing interval of four hours. Standard instructions indicate that the maximum total daily dose from all sources, including any combination products, must not exceed 4000 mg (4 grams) within any 24-hour period.

Dosing Parameter Standard Parameters
Standard Adult Dose 325 mg to 1000 mg
Minimum Interval 4 hours between doses
Maximum Daily Limit 4000 mg (4 g) total

Specific Usage Contexts

The medicine can be taken with or without food. Administration requirements vary by the pharmaceutical form: liquid suspensions must be accurately measured using the dosing device provided, and extended-release tablets must be swallowed whole without crushing or dissolving. For pediatric patients, dosing is weight-based, calculated as 10 to 15 mg/kg per dose. Usage instructions also define adjustments for specific patient groups; for instance, patients with severe renal impairment may require the dosing interval to be extended, such as to eight hours in some clinical protocols.

Recent Clinical Evidence

Recent Clinical Evidence for Par

Clinical studies have investigated the role of Par (Drug X) across its approved indication spectrum, focusing primarily on its observed effects in relieving mild to moderate pain and reducing fever.

Evidence from multiple randomized controlled trials (RCTs) suggests that Par administration is associated with statistically significant reductions in measured pain intensity compared to placebo, particularly within the first few hours following a single dose. These outcomes have been consistently observed across various acute pain models, including headache and dental pain.

Regarding its fever-reducing action, research indicates that Par appears to modulate the thermoregulatory center in the central nervous system, which leads to a lowering of body temperature in febrile patients. Studies assessing its antipyretic properties have typically reported a measurable reduction in temperature within one hour of administration, with the duration of this effect varying between subjects.

Area of Investigation Key Finding (General) Evidence Level (General)
Acute Pain Association with reduced pain scores High
Fever Reduction Observed decrease in body temperature High
Mechanism Modulates central thermoregulation Supported by in vitro and in vivo models

Comparative effectiveness studies have explored Par’s performance relative to other non-prescription analgesics. While some research suggests comparable efficacy for certain pain types and severities, other studies indicate variations in time-to-onset and duration of relief. Overall, the established body of evidence supports Par's role as a widely utilized first-line agent for its primary indications. Ongoing research continues to explore its use in specific patient populations and to refine the understanding of individual response variability.

Key Studies & References

  1. Paracetamol for acute pain in adults: an updated systematic review and meta-analysis
  2. Acetaminophen: A Review of its Pharmacological Properties and Therapeutic Effectiveness
  3. Clinical practice guideline for the relief of pain, fever, and headache (Relevant National/International Guideline)

Frequently Asked Questions (FAQ)

Common questions about Par (FAQ)

Q: Does Par stay in your system for a long time?

Regulatory documents describe how Paracetamol is processed and eliminated by the body. The elimination half-life is typically reported as approximately 1.9 to 2.5 hours in adults. The half-life refers to the time it takes for the concentration of the medicine in the blood to decrease by half.

Q: Is it normal to feel a bit tired when first starting Par?

Official product information does not list fatigue or drowsiness among the common or very common adverse reactions. Regulatory documents also state that Paracetamol generally has no known influence on a person’s ability to drive or operate machinery. If unexpected tiredness occurs, consulting a healthcare professional is consistent with appropriate medical practice.

Q: What is the difference between Par and its active metabolite?

Par (Acetaminophen/Paracetamol) is the medicine that is administered, and the body processes it into other compounds. One of these compounds, called a metabolite, is described in official documents as being involved in the drug's action on central pain pathways.

Q: Is it possible to become dependent on Par?

Par (Acetaminophen/Paracetamol) is officially classified as a non-opioid analgesic and antipyretic. Regulatory documents do not list dependence or addiction as a common or major risk associated with its use as a single-ingredient product.

Q: What is the main difference between Par and other medicines used for the same thing?

Official information indicates that Par (Acetaminophen) is primarily categorized for symptomatic relief of pain and fever. Unlike most Nonsteroidal Anti-inflammatory Drugs (NSAIDs), it is noted to have minimal peripheral anti-inflammatory effects, which distinguishes its action profile.

Q: Why does my doctor call the drug by a different name?

The active substance is known by two international non-proprietary (generic) names: Acetaminophen (common in the U.S.) and Paracetamol (common globally). Prescribers may use one of these generic names or a specific brand name, which varies depending on the region.

Q: Is Par considered a long-term or short-term treatment?

Official guidelines for over-the-counter use recommend Paracetamol for short-term treatment. Regulatory documents typically advise seeking professional guidance if use extends beyond three days, indicating its primary use for acute conditions.

Q: Do I need a special authorization to get a prescription for Par?

Paracetamol is widely available as an over-the-counter (OTC) medicine without a prescription in many regions. However, certain high-strength, combination, or intravenous formulations may be classified as prescription-only, depending on local government regulation.

Q: What are the general recommendations for Par and driving or operating machinery?

Regulatory documents state that Par (Acetaminophen) generally has no known influence on a person’s ability to drive or operate machinery. This information is typically included in official product labeling.

Q: Is it possible for Par to show up on a drug screen?

Paracetamol is a chemical compound that can be detected in biological fluids. Specific drug screening assays approved by regulatory bodies are available and designed to detect the presence of Paracetamol at or above therapeutic concentrations.

Q: Is the brand name of Par the same in every country?

The brand name used to market Paracetamol is not consistent across all countries and is determined by regional manufacturers. The names Acetaminophen and Paracetamol are the internationally recognized generic names, but the trade names will vary.

Q: Can Par affect sleep patterns?

Official product information does not classify Par (Acetaminophen) as a sedative and states that it has no influence on a person’s ability to drive. The drug is primarily classified as an analgesic (pain reliever) and antipyretic (fever reducer).

How should Par be stored and disposed of?

How to Store and Dispose of Par

To ensure product stability, Par (paracetamol/acetaminophen) must be stored at controlled room temperature, typically 20 C to 25 C (68 F to 77 F). Always keep the medicine in a cool, dry place, protected from excessive heat, moisture, and light.

Storage Essentials

  • Keep the product in its original container with the lid tightly closed.
  • Store all forms of Par out of the sight and reach of children.

Disposal Instructions

  • The most recommended method for disposing of expired or unused Par is through a drug take-back program or mail-back service.
  • If a take-back program is unavailable, mix the medicine (do not crush tablets) with an undesirable substance like dirt or coffee grounds, place the mixture in a sealed bag, and dispose of it in the household trash.
  • Do not flush this medication down a toilet or pour it down a sink.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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