1. What are uses of acetaminophen?

Acetaminophen, known as paracetamol, is very familiar in the community as well as in the medical facilities. It is widely used in the treatment of the types of pain which don’t have an organ of origin, and mild to moderate fever.

Acetaminophen is not only an active metabolite of phenacetin but also an effective analgesic – antipyretics that can replace aspirin (one of the nonsteroidal anti-inflammatory drugs is also used to reduce fever and kill pain). However, unlike aspirin, acetaminophen has no inflammatory treatment.

Acetaminophen reduces body temperature in people with a fever, but rarely causes hypothermia in ordinary citizens. It affects the hypothalamus making heat relief and increasing heat radiation due to vasodilation and increasing peripheral blood flow. At therapeutic doses, it has little effect on the cardiovascular and respiratory systems. Moreover, it does not alter the acid base balance, irritate, scratch or bleed the stomach like salicylate. The reason for these is that it does not work on cyclooxygenase of the whole body but the central nervous system. Also, it does not affect platelets or bleeding time.

Through many uses mentioned above, WHO has recognized acetaminophen as the safest and most efficient pain reliever. However, the safety limitation of acetaminophen is a 24-hour period. For healthy adults, the maximum daily dose is 4,000 mg (6-8 tablets, depending on the strength of the drug). Consider dosage less if the patient has severe liver disease.

2. How long does acetaminophen stay in your system?

Increasing the effectiveness and reducing the unwanted effects of acetaminophen, modern medicine has discovered and successfully tested the mechanism of “slow release” and has successfully applied in many countries.

The new mechanism allows acetaminophen to relieve pain quickly in 15 minutes instead of over an hour as traditional medicine.

Initially, about 50% of acetaminophen will be released from the pill to be absorbed into the blood; thereby the patient will reduce the fever and relieve the pain within the first 15 minutes after ingesting.

Within the next 45 minutes, about 25-30% of the drug is released from the pill to be absorbed into the blood. It maintains the amount of acetaminophen in the patient’s body to stop the fever and the pain. In the last 120 minutes, the remaining amount of acetaminophen will continue to be released completely. It maintains the amount of the drug up to eight hours so that the patient does not have a fever and pain again.

The “slow release” mechanism makes the amount of the drug that is released gradually and then absorbed into the blood be fully calculated to ensure the maximum effect of acetaminophen. During that time,  the patient’s liver has enough time to produce sulfates, glucuronic acid, and glutathione which are the beneficial substances for neutralization of hepatic nephrotoxic agent, NAPQI (N-acetyl-p-benzoquinone imine), formed when acetaminophen is oxidized by cytochrome P450 in the liver.

Therefore, the “slow release” mechanism can help lessen damage to the liver when using acetaminophen at high and frequent doses.

3. What are notes to use acetaminophen?

Acetaminophen is usually taken orally. For patients unable to consume, they can use rectal medicines. Note that required rectal dose may be higher than the oral dose to have the same plasma concentration.

Acetaminophen should not be used for self-administration of pain relief for more than ten days in adults or more than five days in children unless there is a direction of a physician since such severe and prolonged pain may be a pathological sign diagnosed, treated and supervised by the doctor.

Do not use acetaminophen for adults and children to self-treat high fever (above 39.5ºC), fever that lasts more than three days, or recurrent fever unless a physician directs because such fever may be a sign of a severe illness which needs to be quickly diagnosed by the doctor.

When using it, the patient should be cautious of other medicines containing acetaminophens, such as other flu medicines or painkillers. And, they should also check the ingredients of those drugs before taking them. Acetaminophen also has a daily dose limitation if taking other medications containing this ingredient at the same time. They need to make sure that all will not exceed the total amount of acetaminophen allowed in one day.

To reduce the risk of overdose, children should not exceed five doses of acetaminophen for pain or fever reduction within 24 hours unless advised by a physician.

For long-lasting acetaminophen tablets, when taking, do not crush, chew or dissolve in liquid.

When using acetaminophen at home, carefully read the instructions for use and check its content in the product to use the correct dose for each subject.

Do not use acetaminophen in patients with anemia or severe heart, lung, kidney or liver disease, hypersensitivity to acetaminophen or glucose-6-phosphate dehydrogenase deficiency.

As prescribed by the World Health Organization (WHO), when starting the pain at any position on the body such as a headache, toothache, ankle sprains, etc., the patient should use the drug whose main ingredient is acetaminophen at first. This medication is rapidly absorbed into the blood, and through the intestinal wall, so the pain will be significantly reduced. Under the effect of acetaminophen, the pain usually stops after about an hour, and after 4 hours, the effect of the drug will run out.

If the patient taking acetaminophen has symptoms such as a rash, blisters, etc., stop taking the medication and go to the medical facility immediately. If the patient has had a skin reaction while taking acetaminophen, do not retake it in the future. Talk to the doctor about the allergic skin reaction to acetaminophen so that the physician can use other antipyretics and painkillers.

When taking acetaminophen, do not drink alcoholic beverages. It will double the damage to the liver because it must work too much. It not only neutralizes NAPQI formed when acetaminophen is oxidized by cytochrome P450 in the liver but also converts alcohol through a series of chemical reactions to eventually produce carbon dioxide and water. From that, it can lead to liver diseases such as hepatitis or cirrhosis.



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