Analgesics are painkillers, and include such medications as aspirin and acetaminophen. Although these types of drugs are commonly used to reduce pain from a headache, their use can actually produce headaches, if used too often. A headache associated with painkiller usage is called an analgesic headache, or an analgesic rebound headache. Scientists, as of 2011, do not yet know the exact mechanism by which these kinds of headaches can arise.
Many conditions which produce chronic pain may be controlled with regular use of analgesics. This includes chronic forms of headache, such as migraine. Patients suffering from these conditions who take painkillers regularly to control the pain, may actually inadvertently suffer from recurrent analgesic headache as a result. Characteristically, an analgesic headache occurs daily, and may be a dull pain rather than an acute pain. The analgesic headache can often be less severe than the condition being treated, but can still contribute to discomfort and a reduction in quality of life.
Doctors can identify the presence of an analgesic headache if the headache disappears after the regular medication is stopped. Commonly, a few weeks is needed for the headaches to reduce and eventually go away. A disadvantage to curing the analgesic headache is that the initial complaint may return, so the patient suffers the pain of intermittent migraines, for example, rather than constant analgesic headache. In addition, some people who take regular painkillers do not suffer from analgesic headaches, so painkiller usage can be beneficial.
A variety of painkillers can produce an analgesic headache as a side effect. Very common medications like aspirin or acetaminophen can cause it, but the non-steroidal anti-inflammatories with painkilling effects such as ibuprofen do not appear to cause headaches. Painkillers specifically derived from ergot for use in migraine treatment tend to produce analgesic headaches, and strong drugs like codeine are also likely to produce this type of headache.
Sometimes, a headache that occurs with the regular use of painkillers may not be due to the active ingredient in the painkiller, but rather to other components of the medication. Caffeine, for example, is a common addition to painkilling medications as its stimulant effects counteract the possible drowsiness from the painkiller. Taking too much caffeine, and then stopping abruptly, can result in caffeine withdrawal symptoms which include headache. A reduction in caffeine intake in drinks, as well as in pain medication products, can therefore be beneficial in treating headaches associated with painkiller usage.