Painkillers or Analgesics describe a class of pharmaceuticals that are used to deaden the sensation of pain in a conscious patient. There are a wide range of painkillers that are tailored to the patient's needs and the possible side effects, generally the severity and type of pain and whether or not the drug has a sedative effect.
Painkillers generally fall into two general categories:
Narcotics - such as Vicodin, Morphine, and Oxycodone. Narcotics work by blocking the uptake of chemicals in nerve fibers that are used to transmit electical pain signals. Narcotics are very effective, but cause drowsiness and can be addictive. They generally must be prescribed by a physician.
Salicilates and Non-Steroidal Anti-Inflammatories - such as Aspirin, Acetaminophen, and Ibuprofen. These block the chemicals in the brain that result in the response to pain. They are generally less effective than narcotics, but rarely cause drowsiness, and are not addictive. However, long term use can cause organ damage. These are generally non-prescription medications.
Often the two types are mixed. Tylenol 3, for example, is a mix of Acetaminophen and Codeine.