What is a pain reliever?

Analgesics are drugs that calm or eliminate pain, blocking or bypassing the reception mechanisms in the brain.
The World Health Organization divides them into three levels:
First level: Non-steroidal anti-inflammatory drugs (NSAIDs), are those that do not contain steroids, their function is to reduce the inflammation and block some pain receptors, by preventing the production of cyclooxygenase enzymes necessary for perceive pain. They also have antipyretic (fever-reducing), anti-inflammatory, and some antiplatelet properties, which reduce the rate of blood clotting. The best known of this type are paracetamol and acetylsalicylic acid (aspirin).
Second Level: Minor opiates, which are synthetic drugs, with less analgesic power, that mimic opiate substances (derived from opium). Due to their effects, they can cause addiction.
Third Level: Opiates, derived from opium, are substances of great analgesic power, since they act on the receptors brain morphines, and do not have a ceiling, that is, if pain increases, simply increase the dose to inhibit it. However, their application must be closely monitored by the doctor, since they depress the nervous system (they are narcotic) and can cause addiction.

Another substance that is also used for analgesic purposes, especially in patients with chronic pain, such as cancer, is cannabis, Marijuana, which acts on the receptors cannabinaceous of the brain, has less marked effects than opiates, but due to its form of administration, generally smoked, the patient can regulate the dose according to needs.
Other drugs that alone have no effects, but in combination can potentiate an analgesic substance. Among these are corticosteroids, antidepressants and anticonvulsants.
The brain can secrete its own pain relievers, called endorphins, which are as powerful as opiates. Dangerous situations, meditation exercises or the placebo effect can do it.