Paracetamol, also known as acetaminophen, is a medication used to treat pain and fever. It is typically used for mild to moderate pain relief. Evidence is mixed for its use to relieve fever in children. It is often sold in combination with other medications, such as in many cold medications. It relieves pain in mild arthritis but does not affect the underlying inflammation and swelling of the joint. Paracetamol may also be used for other purposes not listed in this medication guide.
It is available under several trade names/brand names: Panadol and Tylenol
Drug Fact
Class : Analgesics and antipyretics
Category: Prescription and OTC (Over The Counter)
Uses: treat pain and fever
Consumed by: adults and children
Pregnancy category: B and C
Category B: Either animal-reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).
Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocide ) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.
Dosage form: tablet, injection, syrup, suppository, caplet
Administration
May be taken with or without food.
Reconstitution
IV: Dilute with NaCl 0.9% or glucose 5% to make a concentration of not less than 1 mg/mL.
Incompatibility
Incompatible with acyclovir Na, diazepam, chlorpromazine HCl.
Contraindications
Hypersensitivity. Severe hepatic impairment or active liver disease (IV).
Special Precautions
Patient with known G6PD deficiency, alcohol dependence, chronic malnutrition or dehydration, weight <50 kg; severe hypovolaemia (IV). Renal and hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Thrombocytopenia, leucopenia, neutropenia, pancytopenia, methemoglobinemia, agranulocytosis, angioedema, pain, and burning sensation at the injection site. Rarely, hypotension and tachycardia.
Gastrointestinal disorders: Nausea, vomiting, constipation.
Nervous system disorders: Headache.
Psychiatric disorders: Insomnia.
Skin and subcutaneous tissue disorders: Erythema, flushing, pruritus.
Potentially Fatal: Hepatotoxicity, acute renal tubular necrosis. Rarely, hypersensitivity reactions such as acute generalized exanthematous pustulosis (AGEP), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN).
Pregnancy Category (US FDA)
PO/Rectal: B; IV/Parenteral: C
Monitoring Parameters
Assess patients for a history of liver disease or alcohol abuse.
Overdosage
Symptoms: Pallor, nausea, vomiting, anorexia, abdominal pain, metabolic acidosis, glucose metabolism abnormalities. After 12-48 hours of ingestion, liver damage may become apparent, which may lead to encephalopathy, hemorrhage, hypoglycemia, hypotension, cerebral edema, cardiac arrhythmia, and pancreatitis. Management: Administer activated charcoal within 1 hour of ingestion. Determine plasma paracetamol concentration ≥4 hours after ingestion. IV N-acetylcysteine may be used up to 24 hours after ingestion (most effective if given within 8 hours). As an alternative, oral methionine can also be used if vomiting is not a problem.
Drug Interactions
Decreased absorption with colestyramine. Decreased serum concentrations with rifampicin and some anticonvulsants (e.g. phenytoin, phenobarbital, carbamazepine, primidone). Enhances the anticoagulant effect of warfarin and other coumarins with prolonged use. Increased absorption with metoclopramide and domperidone. Increased serum concentration with probenecid. May increase the serum concentration of chloramphenicol.
Food Interaction
Increased risk of hepatotoxicity with alcohol. Decreased serum concentration with St John’s wort.
Lab Interference
May produce false-positive test results for urinary 5-hydroxy indole acetic acid.
Action
Description: Paracetamol exhibits analgesic action by peripheral blockage of pain impulse generation. It produces antipyresis by inhibiting the hypothalamic heat-regulating center. Its weak anti-inflammatory activity is related to inhibition of prostaglandin synthesis in the CNS.
Synonym: acetaminophen.
Onset: Oral: <1 hour. IV: 5-10 minutes (analgesia); within 30 minutes (antipyretic).
Duration: Oral, IV: 4-6 hours (analgesia). IV: ≥6 hours (antipyretic).
Pharmacokinetics:
Absorption: Well absorbed after oral and rectal administration. Time to peak plasma concentration: Approx 10-60 minutes (oral); 15 minutes (IV); approx 2-3 hours (rectal).
Distribution: Distributed into most body tissues. Crosses the placenta and enters breast milk. Plasma protein binding: Approx 10-25%.
Metabolism: Mainly metabolized in the liver via glucuronic and sulfuric acid conjugation. N-acetyl-p-benzoquinone imine (NAPQI), a minor metabolite produced by CYP2E1 and CYP3A4, is further metabolized via conjugation with glutathione in the liver and kidneys.
Excretion: Mainly via urine (<5% as unchanged drug; 60-80% as glucuronide metabolites and 20-30% as sulfate metabolites). Elimination half-life: Approx 1-3 hours.
Chemical Structure
Storage
Tablet/capsule/suspension/solution: Store between 20-25°C. Do not freeze. Protect from light and moisture. Rectal Supp: Store between 2-25°C. Do not freeze.
ATC Classification
N02BE01 - paracetamol; Belongs to the class of anilide preparations. Used to relieve pain and fever.
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