Paracetamol

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Paracetamol is touted as one of the safest modern medications of all time. It offers pain relief and fever lowering effects similar to aspirin minus the side effects. It has very little side effects or interaction with other substances. Infants and older people can use this drug without complications.

Contents

Nature

Paracetamol is said to inhibit the production of prostaglandin producing enzyme, cyclo-oxygenase (COX) which makes it similar to ibuprofen and aspirin. However, unlike the latter that act on COX-1 and cause gastrointestinal side effects, paracetamol is said to act on COX-3. This ability gives it the analgesic and antipyretic effect that lasts for two to three hours but has no effect on preventing inflammation.

Its empirical formula is represented by C8H9NO2. It has various chemical names: - 4-acetamidophenol, 4-hydroxyacetanilide, or N-acetyl-p-aminophenol. In the United States Pharmacopoeia, paracetamol is synonymous to acetaminophen.

Historical development

Paracetamol is a major metabolite of phenacetin and acetanilide. These substances were used as substitutes to cinchona and willow that were used as natural remedies for fever. Brodie and Axelrod established this fact in 1948.

In general, this drug is derived from coal tar and is chemically classified as an “aniline analgesic.”

Recommended doses

In adults

The recommended adult dose of paracetamol for adults is two 500 mg tablets with four to six hours between doses. It must not exceed eight tablets within 24 hours. This dose may be continued for ten days.

In children

In general, children are given 10 milligrams of paracetamol per kilogram bodyweight. This can be repeated every four or six hours but must not exceed four doses within 24 hours and should not exceed 5 days.

  • For infants younger than three months, paracetamol must be used under medical supervision.
  • For babies three months to one year, 60 to 120 milligrams (2.5 to 5 milliliters syrup) at three to four times daily is recommended.
  • For children ages one to six years old, 120 to 240 milligrams (5 to 10 milliliters syrup) is advised.
  • Children older than 6 years old can take 250 to 500 milligrams, 3 to 4 times daily.

Availability

Paracetamol is sold in the Philippines as a tablet (500 mg per tablet), in syrups (120 milligrams of paracetamol per 5 milliliters), and in ampules. It is commonly sold without prescription when in combination with other drugs like ibuprofen, phenylpropanolamine, dextromethorphan and chlorpheniramine. Popular brands of pure paracetamol are Aeknil ® ampules, Biogesic ® tablets, Calpol ® suspension, and Tempra ® syrup.

Special warnings

Despite its marketing reputation as a “safe drug,” paracetamol is still a drug that has to be used warily.

  • It must be used with caution on patients with liver and kidney diseases.
  • It is also not advisable to use this drug during the first trimester of pregnancy.
  • Nursing women must be under medical supervision for the therapeutic dose and duration of use.
  • Alcohol dependents must be wary of using this medication.

Since paracetamol is often implicated in suicides and drug overdose, methionine and N-acetylcysteine are commonly given to counteract its effects on the liver.

Interactions

These are some drugs that commonly interact with paracetamol:

  • When used with phenobarbital, it might increase its harmful effect on the liver.
  • Contraceptive pills, carbamazapine and rifampicin reduce its medicinal effectivity.
  • Cimetidine increases its analgesic effects and reduces its toxic effect in the liver.
  • Chloramphenicol's effect is increased when used with paracetamol.

Side effects

Unexpected effects rarely occur when taking paracetamol. When they occur, they need to be seen by the doctor.

  • Hypersensitivity reactions (itching and rash) are possible.
  • Nausea, vomiting, sweating, and discomfort are symptoms of toxic hepatitis and will happen only when paracetamol is used long term.

References