The human body is capable of increasing body temperature in response to infection or other triggers. This fever can also occur in some people as a response to medication, in which case it is called "drug fever." Normally, once the medicine is withdrawn, the fever disappears, but it can come back if the medicine is reinstated. Examples of medicines that can cause drug fever include a variety of antibiotics, certain anti-cancer drugs and some anesthetics.
Drug fever appears to be quite common in patients with unexplained fever. Medical explanations for fever include such issues like infection or auto-immune reaction, so these factors can be mistaken for drug fever and vice versa. Treatment generally involves stopping the use of the drug and replacing it with another medication, but if this is not possible then other drugs like corticosteroids may be administered to help reduce the fever.
Patients can develop a high temperature as a reaction from a drug in a few different ways. The most likely cause is that the body's immune response overreacts to the drug molecules inside the body, and produces a feverish reaction in the mistaken impression that the drug is an infectious organism. Some drugs may interfere with the way in which the body keeps its temperature inside a normal range, tricking the body into heating itself up.
Another possible mechanism of drug fever is that the destruction of infectious organisms by the drug produces fever. Bacteria, for example, contain substances called pyrogens in their cell structure, which strongly provoke a feverish response by the immune system. The body does not realize the pyrogens only represent bits of dead organisms, which do not require fever to help kill. Although stringent manufacturing processes help to reduce the presence of bits of dead organisms in medicine products, some may possibly contain pyrogens; when injected, they provoke this same feverish response. Genetics are another reason why drug fever is more likely in some people than other, as the individual response to the drug can vary.
A technique called rechallenge may be employed by doctors to assess whether it is truly a medication that causes a fever. This involves temporary cessation of the drug until the fever declines, and then a fresh administration of the drug. If the fever returns, then drug fever is likely to be the cause of the high temperature. This diagnostic method does, however, carry a risk of side effects from the drug.
