Help > Pain Information > Types of Pain Relievers > Analgesics


Analgesics are medications used to relieve pain without reducing the consciousness of the patient. They work by reducing the amount of pain felt and this is generally achieved by interfering with the way the pain message is transmitted by the nerves. Analgesics will not treat the cause of the pain but they will provide temporary relief from pain symptoms. There are three main categories of analgesics. The first is the opioid analgesics which are prescription only medicines that are very potent, being chemically related to morphine. The second is the non-opioid analgesics. Non-opioid analgesics work by affecting the prostaglandin system, which is the system within the body responsible for producing pain. This category includes non-steroidal anti-inflammatory drugs, or NSAIDs, such as Aspirin, ketoprofen and ibuprofen. The last category is adjuvant analgesics, which are medicines typically used for purposes other than pain relief. This includes some antidepressants that may also help to relieve pain in specific circumstances.It is the second of these three categories of analgesic that is the focus of this website. They are over-the-counter drugs that are can be safely used provided that the recommended dosage restrictions are observed. They are non-habit forming and have an effective ceiling, at which point the patient will derive no further benefit from increasing the dosage. Non-opioid analgesics act peripherally and not centrally like opioids that depress the central nervous system (CNS) and inhibit the brain's ability to feel pain. Non-opioid analgesics target the chemical substances released by the brain in response to injury that facilitate the transmission of the pain stimuli to the brain. The most prevalent of these chemical mediators is prostaglandin. Non-opioid NSAIDs are effective because they serve to block the release of prostaglandin at the peripheral nerve sites.Prostaglandins serve a variety of regulatory functions within the body. One of these functions is to assist the transmission of pain signals to the brain so that you are readily alerted that damage or dysfunction has occurred within the body. Other prostaglandin actions include the regulating body temperature, inflammation, the elasticity of blood vessels and the contraction of smooth muscle tissue.When damage occurs to the body, prostaglandins are formed from the unsaturated fatty acids released by damaged cells. Prostaglandins contain an enzyme called cyclo-oxygenase (COX). Prostaglandin synthetase amplifies the amount of pain experienced by serving as a pain activator. They increase the sensitivity of the nerves to pain impulses. By reducing the synthesis of prostaglandin the amount of pain stimuli sent to the brain is correspondingly reduced.Analgesics like paracetamol and codeine mostly affect the central nervous system (CNS) while NSAIDs like ibuprofen and aspirin are more effective near the actually site of the pain, exerting their analgesic effect in the periphery. Codeine works on the CNS as a weak opiate agonist that inhibits pain signals so that less pain is felt. Codeine achieves this by binding with receptors at various sites in the CNS to alter the chemical process that stimulates pain signals. Paracetamol is a weak prostaglandin inhibitor that blocks prostaglandin biosynthesis in the CNS.NSAIDs like Aspirin, ibuprofen, diclofenac, and ketoprofen block the pain impulse at the source of the pain. They work by hindering the body's ability to biosynthesise prostaglandin by adhering to the cyclo-oxygenase (COX) that controls the amount of prostaglandin produced by the immune system. The special nerve endings that transmit the pain message are sensitised to prostaglandin so, by restricting its presence, the pain message is reduced. This weakens the physiological chemical process that results in the sensation of pain.