Harmful effects of fever (for example, dehydration, changes in consciousness, seizures, or coma) are most likely to occur at temperatures above 106 degrees. Lower fevers are dangerous in persons with heart disease, since fever increases the work of the heart because the pumping of blood must increase. Seizures occur in 2 to 4% of all children between the ages of 6 months and 5 years (usually before age 3) with high fevers though these seizures generally last no more than 15 minutes. Children who experience febrile seizures have a higher risk of developing epilepsy later in life.

What are the different classes of pain relievers and fever reducers?

The three classes of OTC analgesic/antipyretic medications are:

• Salicylates: aspirin (also called acetylsalicylic acid or ASA), choline salicylate, magnesium salicylate, and sodium salicylate;
• Acetaminophen; and
• Nonsteroidal anti-inflammatory drugs (NSAIDs): ibuprofen, naproxen sodium, and ketoprofen. (Aspirin is also an NSAID, but it is considered separately from the other NSAIDs because it has some unique properties.) Each of these drugs is discussed in detail below.

In most circumstances, these medications all have very similar analgesic (pain- relieving) and antipyretic (fever-lowering) abilities. Their onset of action (the interval from the time of ingestion to the start of pain relief) also are similar. Naproxen sodium may have a somewhat longer duration of pain relief (analgesia) than the other NSAIDs or aspirin. At high doses, salicylates and NSAIDs suppress inflammation and are, therefore, particularly useful in treating inflammatory diseases such as arthritis. Acetaminophen does not have anti-inflammatory actions.

Many OTC analgesics are available in combination with other drugs. There is some evidence that caffeine and antihistamines enhance the effects of analgesics. Thus, caffeine increases the pain-relieving effects of aspirin and ibuprofen, and the antihistamines orphenadrine and phenyltoloxamine enhance the pain- relieving effects of acetaminophen. Combinations of decongestants with analgesics are logical only when nasal or sinus congestion are present, for example, for sinus headaches.

Aspirin

Formulations of aspirin: Aspirin can damage the lining of the stomach and duodenum, thereby causing abdominal pain, bleeding, and/or ulcers. As a result, 1 in 5 persons who take aspirin in a dose of 2.5 grams per day or more develops ulcers and about 1 in 6 will lose enough blood from gastrointestinal bleeding to develop anemia. In an attempt to reduce the potential for these complications, some aspirin-containing tablets have been coated with a special coating that prevents the tablet from dissolving until it is past the stomach and duodenum. These "enteric-coated" aspirin products may reduce the frequency of abdominal pain, but not the bleeding or ulcers. Moreover, the onset of pain relief is delayed with enteric-coated aspirin because it takes more time for the tablets to dissolve. Other attempts to prevent complications have included aspirin-containing products that release the aspirin slowly over time (e.g., Zorprin; Measurin; Verin). Like enteric-coated products, these products are not ideal when prompt relief of pain is needed. They also do not prevent ulcers or bleeding. Buffered (e.g. Bufferin) and effervescent (e.g. Alka-Seltzer) aspirin products are absorbed more quickly from the stomach and intestine than aspirin, but they do not act more rapidly than regular aspirin and do not reduce the risk of bleeding or ulcers. Furthermore, effervescent aspirin products contain large amounts of sodium (salt) and should be avoided in persons with high blood pressure, heart failure, or certain kidney diseases.

Side Effects: Aspirin prevents platelets from sticking together and forming blood clots. On the one hand, this effect can be used beneficially, for example, to prevent the blood clots that cause heart attacks or strokes. On the other hand, by preventing blood clots, aspirin can have the detrimental effect of promoting bleeding. Therefore, aspirin should not be used by people who have diseases that cause bleeding (e.g., hemophilia, severe liver disease) or diseases in which bleeding may occur as a complication (e.g., stomach ulcers). Moreover, since the effect of aspirin on platelets lasts for several days, people should not take aspirin for seven days before surgical or dental procedures because of the increased risk of bleeding after the procedures. In patients at risk for bleeding, acetaminophen can be an excellent alternative to aspirin since acetaminophen does not have an effect on platelets, blood clots, or bleeding. Like aspirin, other NSAIDs affect platelets, but the duration of the effect is less than with aspirin. Two aspirin-related, salicylate-containing products (salsalate and choline magnesium trisalicylate) have no effect on the platelets, but they are available only by prescription.

Although many people claim to be "allergic" to aspirin, most describe their "allergy" as abdominal pain or heartburn. These common side effects are not allergies, but rather reflect the irritating effects of aspirin on the lining of the stomach. True allergy to aspirin occurs in fewer than 1 out every 100 persons. True allergy may include hives, itching, swelling, or difficulty breathing. Allergy to aspirin is more common in persons with asthma, allergic rhinitis, or nasal polyps. In such persons, the risk of an allergic reaction to aspirin may be as high as 1 to 3 persons out of every 10. People with true aspirin allergy also may be allergic to other compounds. One such compound is tartrazine, or yellow dye #5. This dye is used in many medicines, foods (such as soft drinks), and candy or desserts. In addition, people with an allergy to aspirin often are allergic to other NSAIDs, such as ibuprofen.