One of the most common reasons for such system failure is the daily intake of painkillers, or analgesics. Research in many headache centers around the world has shown that patients who use analgesics more than two to three days per week suppress this antinociceptive activity. They therefore need to rely upon the painkilling properties of the drug more and more as their own body's ability to suppress the perception of pain diminishes. A vicious circle of drug dependence then develops in which the patient has a constant headache which will get worse if he or she does not consume the drug, but is never completely relieved. This is known a drug-induced headache.
Analgesics become completely ineffective painkillers.
A complicating feature of drug-induced headache is that other nonanalgesic treatments are usually ineffective as well as long as the patient takes analgesics. This is because these drugs are aimed at the same antinociceptive system that the analgesics are blocking. Once the patient is withdrawn from the analgesics, the pathway is reopened, and medications which did not work in the past may improve the overall headache. Remember that analgesics can be obtained both by prescription and off the shelf. Use any of these products no more than twice per week.