Antipyretic Drugs

Antipyretics are drugs whose chemical composition is intended to control fever. They have the ability to restore body temperature to normal levels after an increase in it has occurred. They are also known as antipyretics or fever reducers.

Some antipyretics also have analgesic and anti-inflammatory properties that reduce the general discomfort that often accompanies fever. However, although they are effective in lowering the temperature, the cause that has caused it does not disappear with its sole action.

When are antipyretic drugs used?

Remember that fever occurs when the immune system identifies pathogens. It then activates certain mechanisms in the hypothalamus that cause the temperature to exceed its normal level. The hypothalamus, which is a structure of the brain, is responsible for regulating body temperature, among other functions.

In general terms, a person can be considered to have a fever when their temperature is above 38 ºC. Between 37 and 38 ºC is considered a low-grade fever. Although there has been a bad habit of administering these drugs to any degree of fever, the truth is that it is not always the most appropriate.

As the article ‘Antipyretics’, published in the Professional Pharmacy magazine indicates, fever is a protective mechanism of the body. It means that the immune system is working to deal with certain pathogens.

On the other hand, it can also be the manifestation of another more serious disease that is happening in the body. In these cases, antipyretics can mask and hide other pathologies.

The decision about which type of antipyretic to use is based on the mechanism of action of the different drugs, their pharmacodynamics, their efficacy, and their possible side effects. Therefore, antipyretics should be prescribed by a doctor and should not be used without a prescription.

In mild fever, that is, when the fever is below 38 ºC, the use of antipyretics is not recommended to reduce it. Despite the fact that antipyretics control fever, it is essential to address the original cause that generated it to ensure that the patient recovers.

Classification of antipyretics

Depending on their chemical composition and the properties they present, the most important antipyretics can be classified into 4 main groups : salicylates, pyrazolones, aminophenols and derivatives of propionic acid.

Salicylates, such as acetylsalicylic acid

Salicylates  have antipyretic action, but also analgesic and antiplatelet action. Aspirin or acetylsalicylic acid belongs to this group.

These drugs produce irreversible inhibition of cyclooxygenase, which is an enzyme that produces prostaglandins and mediators of inflammation.

• The oral dose of salicylates produces effects within half an hour. Its effects can last up to 6 hours.
• They should not be taken on an empty stomach, but accompanied by some food.
• Salicylates should be used with caution as they can lead to poisoning.
• They are contraindicated in people with a history of  gastric ulcers, due to the gastric damage they can cause. Also, in the postoperative case , due to its antiplatelet properties.
• They should not be used in asthmatic people.
• They should not be used in children with viral infections, chickenpox or flu because they can cause the appearance of Reye’s syndrome.
• Care should be taken if you are being treated with other medications, as significant interactions can occur.

Pyrazolones, such as metamizole

Pyrazolones are used to treat fever when it is accompanied by pain, since they are analgesic and antipyretic. Among the most popular, metamizole or dipyrone, also known as nolotil, stands out.

• Pyrazolones work in a similar way to aspirin, but their anti-inflammatory effects are more far-reaching and less damaging to the stomach.
• In some countries, pyrazolones have been withdrawn from the market because they can cause agranulocytosis and aplastic anemia, among other serious adverse reactions.
• They can cause hypotension and produce allergic reactions. In high doses, they cause liver and kidney toxicity.

Aminophenols, such as acetaminophen

Paracetamol, also known as acetaminophen, has antipyretic and analgesic properties. Unlike the previous ones, it is not anti-inflammatory. It has established itself as the drug of first choice for mild to moderate pain and fever.

• It inhibits hypothalamic cyclooxygenase more selectively than other drugs, which means that it has little gastrointestinal adverse effects or anti-inflammatory effects.
• It does not damage the stomach lining, so it can be administered in patients with gastrointestinal problems.

• Abusing its consumption can lead to liver failure.

Derivatives of propionic acid, such as ibuprofen

Medicines derived from propionic acid, such as ibuprofen, have analgesic effects similar to those of aspirin, but their anti-inflammatory and antipyretic action is inferior.

• They are part of the non-steroidal anti-inflammatory drugs (NSAIDs) and are frequently used in the treatment of muscle and joint pain.
• Propionic acid is rapidly absorbed through the gastrointestinal tract. Its administration can be done every 6 or 8 hours.
• Some side effects that can occur are mainly gastrointestinal, such as diarrhea, vomiting, constipation or peptic ulcer.

• Excessive intake of these types of drugs can cause toxicity.
• In more serious cases, these types of drugs are associated with liver and kidney failure.

Recommendations for the use of antipyretics

In general terms, antipyretics should be used only when the fever exceeds 38ºC. More specifically, we can say that they should only be used when the fever causes discomfort.

Also, to avoid unwanted effects, it is important to consider some precautionary measures when administering them:

• They should be consumed with water, never with coffee, soft drinks or alcoholic beverages. In general, it is recommended to administer them with food.
• People with gastritis, ulcers or digestive conditions should only take antipyretics that are harmless to the stomach lining, such as paracetamol. Another option that your doctor may recommend is to use a gastric protector, such as omeprazole, if necessary.
• In case of pregnancy and lactation they should be avoided if possible and consult a doctor before taking them.

• People with a history of allergies, respiratory problems and kidney problems should avoid its consumption.
• In case of being treated with other medications, care should be taken with the administration of antipyretic drugs. In each case, the doctor will indicate what to do.
• Children with viral infections, chickenpox, or the flu should not take medications containing aspirin, as they are linked to the development of Reye’s syndrome.

If the fever is mild -febric- it can be treated with physical methods, such as cold water washcloths or baths. If this rises, it is advisable to go to the doctor so that he analyzes the possible cause. If necessary, he will prescribe the most advisable antipyretic for each case.