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There are two primary types of analgesics: narcotic (opioid) and non-narcotic (nonopioid) analgesics.

Non-narcotic (nonopioid) analgesics are drugs that have principally analgesic, antipyretic, and anti-inflammatory actions. They do not bind to opioid receptors and are not classified under the Controlled Substances. They are milder forms of the painkiller. Non-narcotic drugs include acetaminophen, the most commonly used over-the-counter non-narcotic analgesic. Other drugs are not technically part of the analgesic family, but are nonetheless considered analgesics in practice. These include nonsteroidal anti-inflammatory drugs (NSAIDs). Aspirin and acetaminophen are two of the most widely used analgesics and are effective for mild to moderate headache and pain of musculoskeletal origin.

Acetaminophen and NSAIDs provide effective relief of many types of acute and persistent pain. Prescribed alone, these agents can relieve many types of mild to moderate pain. Alternatively, for moderate to severe pain, they can be used in combination with opioid drugs to enhance pain relief.

Non-opioid agents differ from opioid analgesics in several ways:

• non-opioids have a ceiling effect in analgesia (a maximum dose beyond which analgesic effect does not increase)
• do not produce tolerance or physical dependence and are not associated with abuse or addiction
• they are antipyretic and all except acetaminophen are anti-inflammatory agents
• the primary mechanism of action of non-opioid analgesics is inhibition of prostaglandin formation

They are useful for everyday aches and pains, such as headaches, joint and muscle pain. Narcotic (opioids) are stronger analgesics that are used when pain signals are too severe to be controlled by non-narcotic analgesics. All narcotic analgesics are prescription medications.

The primary difference has to do with how they produce their analgesic effects. The opioid drugs reduce pain by working on special pain receptors in the nervous system, primarily located in the brain and spinal cord. The non-opioids, on the other hand, work more directly on injured body tissues. The opioids decrease the brain's awareness of the pain, whereas the non-opioids affect some of the chemical changes that normally take place wherever body tissues are injured or damaged. These chemical changes at the site of the injury typically result in inflammation and increased pain sensitivity.

The long-term use of opioids can lead to dose escalation. Tolerance refers to the fact that the drug loses it’s pain relieving effectiveness when used over time. That is, tolerance occurs when you need to take more of the drug in order to obtain the same degree of pain relief. However, tolerance is also not considered to be a problem by most pain specialists. Many persons with chronic pain who are taking opioids are able to maintain their dosage level without continuing escalating the amount taken.

Physical dependence is an automatic consequence of taking opioids over time. Physical dependence is apparent when one abruptly stops taking the drug or reduces the amount taken. This leads to withdrawal reactions. Physical dependence is not the same as addiction and is not considered to be a problem by most pain specialists.

Although non-opioid pain relievers are often preferred for most types of chronic pain, they have two serious drawbacks. The first drawback has to do with ceiling effects. Non-opioids have upper limit of pain relief that can be achieved. Once that upper limit or ceiling is reached, taking additional medication will not provide any further pain relief. Opioids, on the other hand, tend not to have a ceiling. That is, the more you take, the more pain relief you will get. It is for this reason that non-opioids are effective only for mild to moderate pain, whereas opioids are useful for more severe pain intensity.

The second major drawback of the non-opioids are their side effects. Although most non-opioids are quite safe when used for temporary acute pain, problems may arise when people take them over a long period of time (for chronic pain). This is especially true when large quantities of non-opioids are taken. Most are aware of the adverse effects of these drugs on the gastrointestinal system. However, excessive use of the non-opioids can also damage your liver or your kidneys. Opioids have negative side effects as well. However, it is interesting that many pain specialists now believe that opioids, when used as prescribed, are often safer than the non-opioids. Side effects of the opioids include respiratory depression, dizziness, nausea, vomiting, constipation, sedation, and mental clouding. Many of these side effects can be minimized or eliminated with proper medical management.