How Are Analgesic Drugs Classified

Analgesics are one of the most commonly used pharmacological groups. Next, we’ll classify them by their mechanism of action and explain their usefulness.
How are analgesic drugs classified

The word analgesia means the denial or lack of pain . The purpose of analgesic medications is to relieve pain. According to the International Association for the Study of Pain (IASP), pain is defined as an unpleasant sensory and emotional experience. This experience is associated with an actual or potential tissue injury.

There are two types of pain: acute and chronic. They differ in terms of sensory experience, and also in terms of the emotional experience they imply. Thus, they require different analgesic medications.

Acute pain comes from tissue damage and disappears as it heals. An example of acute pain is postoperative pain. On the other hand, it is difficult to find a specific tissue injury that justifies chronic pain. Furthermore, they extend a lot in time. Examples of chronic pain are migraine or osteoarthritis.

As we have already indicated, the emotional component is different in acute and chronic pain. In the case of acute pain, irritability, anxiety and anger are common. In the context of chronic pain, feelings more prone to depression are experienced. Sometimes these emotional symptoms can also be treated. Which is especially common in chronic pain.

Primary analgesic medications

relieve pain
One positive aspect of pain relievers is that they are so varied.

Anti-inflammatory analgesics (NSAIDs)

NSAIDs owe their function to the blockade they effect on the cyclooxygenase (COX) enzyme. They prevent COX from synthesizing some substances related to the inflammatory process, thus managing to stop it. Examples of NSAIDs are acetylsalicylic acid (aspirin) or ibuprofen.

But there are different types of COX, each with its own function, and there are pain medications that block each type specifically. These medications are called selective COX inhibitors (selective iCOX). Examples of them are celecoxib and rofecoxib.


Opioid analgesic drugs activate specific receptors. In general, when an opioid receptor is activated, it makes nerve transmission difficult. Thus, an activated opioid receptor decreases nerve transmission of pain.

There are different types of opioids depending on their efficiency and other characteristics. Thus, we find:

  • Pure agonists: the most effective. Some examples are: Morphine, Codeine and Methadone.
  • Antagonist agonists: slightly less effective. One example is Buprenorphine.
  • Agonist antagonists: activate some opioid receptors and block others. An example is Pentazocine.
  • Mixed: these have other functions besides opioids. One example is Tramadol.

Opioids often produce undesirable effects such as nausea, constipation or sedation.

Secondary analgesic medications

The main purpose of secondary pain relievers is not to relieve pain. In fact, they were generally invented to alleviate other ailments. However, they can alleviate some specific type of pain.


doctor and medicine
Many of these medications must be prescribed by a doctor.

As we have already explained, it is common to associate depressive symptoms with pain, especially chronic pain. Antidepressants can be beneficial in this regard. One of the most used is Amitriptyline.


Antiepileptic drugs reduce nerve transmission. When using them, the nerve transmission of pain decreases. Some of the most used are Carbamazepine and Lamotrigine.

muscle relaxants

Muscle relaxants may be beneficial, especially in muscle pain. If the source of the pain is a contracture or similar, when using them the muscle will relax and the pain will decrease.

In addition, in these cases, they help to get the solution to the pathology. Muscle relaxants commonly used are: diazepam, gabapentin and topiramate.

local anesthetics

Local anesthetics block nerve transmission in the area where they are applied. Thus, using local anesthetics in the original area of ​​pain, the pain will disappear or lessen.

They can also be applied to structures through which the painful impulse passes on its way to the higher nerve centers. This way the pain will not become serious, at least in part. Local anesthetics frequently used are Lidocaine and Pilocarpine.


an effect similar to NSAIDs in that they act to inhibit or decrease inflammation. By decreasing inflammation, the pain caused by it will decrease. A commonly used Corticosteroid is Prednisone.

Analgesics are very varied and useful


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