Acetaminophen
Acetaminophen: instructions for use and reviews
- 1. Release form and composition
- 2. Pharmacological properties
- 3. Indications for use
- 4. Contraindications
- 5. Method of application and dosage
- 6. Side effects
- 7. Overdose
- 8. Special instructions
- 9. Application during pregnancy and lactation
- 10. Use in childhood
- 11. In case of impaired renal function
- 12. For violations of liver function
- 13. Use in the elderly
- 14. Drug interactions
- 15. Analogs
- 16. Terms and conditions of storage
- 17. Terms of dispensing from pharmacies
- 18. Reviews
- 19. Price in pharmacies
Latin name: Acetaminophen
ATX code: N02BE01
Active ingredient: paracetamol (paracetamol)
Manufacturer: Watson Laboratories Inc. (Watson Laboratories, Inc.) (USA), Privat Formulation Inc. (Private Formulations, Inc.) (USA)
Description and photo update: 2019-02-09
Acetaminophen is a drug that has analgesic, antipyretic and anti-inflammatory effects.
Release form and composition
The drug is produced in the form of tablets (12 or 30 pcs. In a package, complete with instructions for the use of acetaminophen).
Active ingredient: paracetamol, in 1 tablet - 500 mg.
Pharmacological properties
Pharmacodynamics
The active ingredient of Acetaminophen is paracetamol, an analgesic-antipyretic, which has an analgesic, antipyretic and weak 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 gastrointestinal tract (gastrointestinal tract), mainly in the small intestine, mainly by passive transport. As a result of a single dose of 500 mg of paracetamol, its C max (maximum concentration) in the 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 body fluids, with the exception of cerebrospinal fluid, and in tissues, with the exception of lipid tissue.
Paracetamol binds to plasma proteins at a level of <10%, which slightly increases with an overdose. Moreover, its sulfate and glucuronide metabolites do not bind to plasma proteins even at relatively high concentrations.
The biotransformation of paracetamol occurs mainly in the liver by conjugation with glucuronide and sulfate, as well as oxidation with the participation of mixed liver oxidases and cytochrome P 450.
In the liver and kidneys, under the action of mixed oxidases, a hydroxylated metabolite with a negative effect is formed in very small quantities - N-acetyl-p-benzoquinone imine, which is usually detoxified by binding with glutathione, but can accumulate in case of an overdose of paracetamol and cause tissue damage.
In adult patients, paracetamol is associated primarily with glucuronic acid, to a lesser extent with 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 predominates.
The half-life (T 1/2) is from 1 to 3 hours. In liver cirrhosis, T 1/2 is slightly higher. The indicator of the renal clearance of paracetamol is 5%.
The substance is excreted in the urine, mainly as glucuronide and sulfate conjugates. Less than 5% of paracetamol is excreted in the form of an unchanged substance.
Indications for use
Acetaminophen is used to relieve pain in 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
Absolute:
- Severe renal and hepatic impairment;
- Anemia;
- Chronic alcoholism;
- Children under 12 years of age;
- Hypersensitivity to drug components.
Relative (Acetaminophen is used with caution):
- Kidney / liver dysfunction;
- 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.
It is not recommended to exceed the maximum daily dose of 4 g and to continue taking the drug for more than 5-7 days.
Side effects
The use of acetaminophen can cause the following side effects:
- Dyspeptic symptoms from the gastrointestinal tract;
- Thrombocytopenia, agranulocytosis, leukopenia, neutropenia, pancytopenia;
- Allergic reactions, manifested as itchy skin, rash and hives.
Overdose
Symptoms of a paracetamol overdose in the first 24 hours are nausea, vomiting, pallor, pain in the abdominal region; 12–48 hours later, kidney and liver dysfunctions with the development of liver failure (up to encephalopathy, coma, death), as well as pancreatitis and cardiac arrhythmias are possible. Liver damage in adults is possible when taking paracetamol in doses of 10 g or more.
Oral methionine or intravenous N-acetylcysteine is recommended.
In patients with non-cirrhotic alcoholic liver disease, the risk of acetaminophen overdose increases.
special instructions
If it is necessary to use acetaminophen during pregnancy, impaired 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, since they may contain paracetamol, as well as with oral glucocorticosteroids, anticoagulants and acetylsalicylic acid.
Influence on the ability to drive vehicles and complex mechanisms
During the period of drug therapy, performing potentially dangerous types of work that require speed of psychomotor reactions and high concentration of attention (such activities include the work of a dispatcher, an operator, driving a vehicle, working with moving mechanisms), you must be careful.
Application during pregnancy and lactation
It has been clinically proven that paracetamol penetrates the placental histohematogenous barriers, but so far its negative effect on the fetus in humans has not been noted.
Paracetamol passes into breast milk in an amount of 0.04–0.23% of the dose taken by the mother.
In experimental studies, the teratogenic, mutagenic and embryotoxic effects of paracetamol have not been established.
If it is necessary to use acetaminophen during pregnancy and lactation (breastfeeding), it is necessary to carefully balance the expected benefits of therapy for the mother with the potential risk to the fetus / child.
Pediatric use
In pediatric practice, the use of acetaminophen is possible according to indications according to the prescribed dosage regimen for the treatment of children and adolescents over the age of 12 years.
With impaired renal function
Acetaminophen is contraindicated in patients with severe renal impairment.
In case of impaired renal function, the drug is used with caution.
For violations of liver function
Acetaminophen is contraindicated in patients with severe hepatic impairment.
In case of impaired liver function, the drug is used with caution.
Use in the elderly
Elderly patients need to be careful when taking acetaminophen.
Drug interactions
- Inducers of microsomal liver enzymes, agents with hepatotoxic effects: increase the risk of hepatotoxic effects of paracetamol;
- Anticoagulants: can slightly or moderately increase prothrombin time;
- Anticholinergics: may reduce the absorption of paracetamol;
- Oral contraceptives: accelerate the excretion of paracetamol from the body with a possible inhibition of its analgesic efficacy;
- Uricosuric drugs: paracetamol reduces their effectiveness;
- Activated carbon: reduces the bioavailability of paracetamol;
- Diazepam: its excretion may decrease;
- Zidovudine: there have been reports of increased myelodepressant action; described a case of severe liver toxicity;
- Isoniazid: manifestations of the toxic effect of paracetamol were observed;
- Carbamazepine, phenytoin, phenobarbital, primidone: reduce the effectiveness of paracetamol with an increase in its metabolism (glucuronization and oxidation) and increased excretion from the body; there have been cases of hepatotoxicity due to the simultaneous use of paracetamol with phenobarbital;
- Cholestyramine: if used for less than 1 hour after taking paracetamol, absorption of the latter may decrease;
- Lamotrigine: its excretion from the body is moderately increased;
- Metoclopramide: may increase the absorption of paracetamol and increase its concentration in blood plasma;
- Probenecid: may reduce the clearance of paracetamol;
- Rifampicin, sulfinpyrazone: may increase the clearance of paracetamol due to the acceleration of its metabolism in the liver;
- Ethinylestradiol: increases the absorption of paracetamol in the intestines.
Analogs
Acetaminophen analogs are Paracetamol, Panadol, Calpol, Efferalgan, Mexalen.
Storage conditions and periods
Store at room temperature in a dry place out of the reach of children.
The shelf life is 3 years.
Terms of dispensing from pharmacies
Dispensed by prescription.
Reviews about acetaminophen
Since the registration period for the drug has expired a long time ago, there are practically no reliable reviews about acetaminophen.
Price for Acetaminophen in pharmacies
The drug is currently not available on the market, so the price of acetaminophen is unknown.
The cost of the most popular analogue - Paracetamol is: 200 mg tablets, 10 pcs. in the package - 3-5 rubles; tablets 500 mg, 10 pcs. in the package - 5–7 rubles.
Maria Kulkes Medical journalist About the author
Education: First Moscow State Medical University named after I. M. Sechenov, specialty "General Medicine".
Information about the drug is generalized, provided for informational purposes only and does not replace the official instructions. Self-medication is hazardous to health!
