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Acetaminophen – a drug that has analgesic, antipyretic and anti-inflammatory effect.

Form of issue and composition

The drug is released in the form of tablets (12 or 30 pieces per pack complete with instructions for the use of acetaminophen).

Active ingredient: paracetamol, in 1 tablet – 500 mg.

Pharmacological properties

Pharmacodynamics

Active component of Acetaminophen is paracetamol, an analgesic-antipyretic, which has analgesic, antipyretic and mild anti-inflammatory effect. The mechanism of action is associated with inhibition of the synthesis of Pg (prostaglandins) and a decrease in the excitability of the center of thermoregulation of the hypothalamus.

Pharmacokinetics

After oral administration, paracetamol is rapidly absorbed from the digestive tract (gastrointestinal tract), mainly in the small intestine, mainly through passive transport. As a result of a single dose of 500 mg of paracetamol, its C max (maximum concentration) in blood plasma is reached after 10-60 minutes and is ~ 6 μg / ml, after which it gradually decreases.

The substance is widely distributed mainly in the liquid media of the body, with the exception of cerebrospinal fluid, and in tissues, with the exception of lipid tissue.

With plasma proteins, paracetamol binds at a level <10%, which slightly increases with an overdose. Moreover, its sulfate and glucuronide metabolites with plasma proteins do not bind even at relatively high concentrations.

Biotransformation of paracetamol occurs predominantly in the liver by conjugation with glucuronide and sulfate, as well as oxidation involving mixed liver oxidases and cytochrome P450.

In the liver and kidneys, mixed hydroxides are produced in very small amounts by a hydroxylated metabolite with a negative effect, N-acetyl-p-benzoquinonimine, which is usually detoxified by binding to glutathione but can accumulate in case of paracetamol overdose and cause tissue damage.

In adult patients, paracetamol binds primarily to glucuronic acid, to a lesser extent – to sulfuric acid. The resulting conjugated metabolites are biologically inactive. In the metabolism of premature infants, newborns and children of the first year of life, the sulfate metabolite of paracetamol prevails.

The half-life (T1 / 2) is from 1 to 3 hours. With liver cirrhosis, T1 / 2 is slightly higher. The index of renal clearance of paracetamol is 5%.

Excreted substance with urine, mainly as glucuronide and sulfate conjugates. In the form of unchanged substance, less than 5% of paracetamol is excreted.

Acetaminophen: Indications for use

Acetaminophen is used to relieve pain during the following diseases / conditions:

  • Migraine;
  • Injuries;
  • Dysmenorrhea;
  • Neuralgia;
  • Toothache and headache;
  • Myalgia;
  • Arthralgia.

Also, acetaminophen is used for infectious and inflammatory diseases accompanied by febrile conditions.

Contraindications for Acetaminophen use

Absolute:

  • Pronounced renal and hepatic insufficiency;
  • Anemia;
  • Chronic alcoholism;
  • Children up to 12 years;
  • Hypersensitivity to the components of the drug.

Relative (Acetaminophen is used with caution):

  • Impaired renal / hepatic function;
  • Benign hyperbilirubinemia;
  • Viral hepatitis;
  • Alcoholic liver damage;
  • Pregnancy;
  • Breastfeeding (lactation period);
  • Elderly age.

Acetaminophen, instructions for use: method and dosage

Acetaminophen tablets are taken in a dose of 500 mg 3-4 times a day.

Do not exceed the maximum daily dose of 4 g and continue taking the drug for longer than 5-7 days.

Acetaminophen Side effects

Acetaminophen can cause the following side effects:

  • Dyspeptic phenomena from the gastrointestinal tract;
  • Thrombocytopenia, agranulocytosis, leukopenia, neutropenia, pancytopenia;
  • Allergic reactions, manifested as a pruritus, rash and hives.

Acetaminophen Overdose

Symptoms of an overdose of paracetamol in the first 24 hours are nausea, vomiting, pallor, pain in the abdominal region; after 12-48 h, kidney and liver function disorders may occur with the development of hepatic insufficiency (up to encephalopathy, coma, fatal outcome), as well as pancreatitis and cardiac arrhythmias.

Liver involvement in adults is possible with paracetamol in doses of 10 g or more.

It is recommended to take methionine inside or intravenous injection of N-acetylcysteine.

In patients with noncirrhotic alcoholic liver diseases, the risk of acetaminophen overdose increases.

Special instructions for Acetaminophen use

If it is necessary to use Acetaminophen during pregnancy, violations of liver and kidney function, Gilbert’s syndrome, as well as in old age, it is recommended to reduce the daily dose and shorten the duration of the drug.

Caution should be exercised while taking the drug with other anti-inflammatory and antipyretic drugs, because they can contain paracetamol, as well as with oral glucocorticosteroids, anticoagulants and acetylsalicylic acid.

Influence on ability to manage motor transport and complex mechanisms

During the period of drug therapy, carrying out potentially dangerous jobs requiring rapidity of psychomotor reactions and high concentration of attention (such activities include the dispatcher’s work, the operator, the management of vehicles, work with moving mechanisms), care must be taken.

Acetaminophen use in pregnancy and lactation

It has been clinically proven that paracetamol penetrates the placental histohematological barriers, but to date, its negative impact on the fetus has not been observed in humans.

Paracetamol penetrates into breast milk in an amount of 0.04-0.23% of the dose taken by the mother.

In the course of experimental studies, teratogenic, mutagenic and embryotoxic effects of paracetamol have not been established.

If acetaminophen is to be used during pregnancy and lactation (breastfeeding), the expected benefit of therapy for the mother with potential risk to the fetus / child must be carefully correlated.

Use of Acetaminophen for children

In pediatric practice, the use of acetaminophen is possible according to the prescribed dosage regimen for the treatment of children and adolescents over the age of 12 years.
In case of violations of kidney function

  • Patients with severe renal failure to use Acetaminophen is contraindicated.
  • For violations of kidney function, the drug should be used with caution.

With violations of liver function

Patients with severe hepatic insufficiency to use Acetaminophen is contraindicated.

For violations of liver function, the drug should be used with caution.

Using Acetaminophen in old age

Elderly patients should be careful when taking acetaminophen.

Acetaminophen and Drug Interactions

Inductors of microsomal liver enzymes, agents with hepatotoxic action: increase the risk of hepatotoxic effects of paracetamol.

Other interactions:

  • Anticoagulants: are able to slightly or moderately increase prothrombin time;
  • Anticholinergics: can reduce the absorption of paracetamol;
  • Oral contraceptives: accelerate the excretion of paracetamol from the body with possible oppression of its analgesic efficacy;
  • Uricosuric means: paracetamol reduces their effectiveness;
  • Activated carbon: reduces the bioavailability of paracetamol;
  • Diazepam: its excretion may decrease;
  • Zidovudine: there have been reports of an intensification of myelodepressive action; a case of toxic damage of a liver of a serious degree is described;
  • Isoniazid: manifestations of toxic effects of paracetamol;
  • Carbamazepine, phenytoin, phenobarbital, primidone: reduce the effectiveness of paracetamol with increasing its metabolism (glucuronization and oxidation) and increased excretion from the body; there have been cases of hepatotoxicity due to simultaneous use of paracetamol with phenobarbital;
  • Kolestyramine: if used for less than 1 hour after taking paracetamol, the absorption of the latter may decrease;
  • Lamotrigine: moderately increased its excretion from the body;
  • Metoclopramide: can increase the absorption of paracetamol and increase its concentration in the blood plasma;
  • Probenecid: may reduce the clearance of paracetamol;
  • Rifampicin, sulfinpyrazone: can increase the clearance of paracetamol due to the acceleration of its metabolism in the liver;
  • Ethinyl estradiol: increases the absorption of paracetamol in the intestine.

Acetaminophen Analogues

Analogues of Acetaminophen are Paracetamol, Panadol, Kalpol, Efferalgan, Meksalen.

Terms and conditions of storage

  • Store at room temperature in a dry place inaccessible to children.
  • Shelf life – 3 years.

Conditions of leave from pharmacies

It is released by prescription.




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