What are Analgesics and its Classification? NCERT Chemistry Class 12

Analgesics and its Classification NCERT Chemistry Class 12

What are Analgesics and its Classification? NCERT Chemistry Class 12

What is Analgesics?

Analgesics (known as painkillers) are a class of drugs that are generally used to reduce or relieve pain. It also remedies any displeasing emotional and sensory experience in a human body which is caused due to tissue damage or expressed in terms of such damage. The term “Analgesic” is derived from two Greek words“an” means without and “algos” means pain. So, analgesics are therapeutic substances that diminish or reduce pain.


When part of the body is injured or suffering from pain, special nerve endings send pain messages back to the brain. Painkilling drugs interfere with these messages, either at the site of the injury, in the spinal cord or in the brain itself. Many painkillers are based on one of two naturally occurring drugs: aspirin and opiates. Aspirin ,also known as acetylsalicylic acid (ASA) is a mild analgesic and work by indirectly blocking the enzyme-controlled synthesis of Prostaglandins(Prostaglandins are hormone-like substances that participate in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure, and modulation of inflammation). By restricting the synthesis of Prostaglandins, mild analgesics can reduce pain, fever, and inflammation. Chemical painkillers such as Endorphins and Enkephalins are produced naturally in the body. Aspirin uses a chemical found in willow bark, used by the Ancient Greeks to relieve pain. Opiates (any drug derived from opium), all work in a similar way to opium, which is extracted from poppies.

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Paracetamol (Acetaminophen)

Paracetamol, also known as acetaminophen or APAP, is used to treat pain and fever. It is typically used for mild to moderate pain. In combination with opioid pain medication, paracetamol is now used for more severe pain such as cancer pain and after surgery. It is used either by mouth or rectally. It is also available intravenously. The effects last for two and four hours. Paracetamol is a mild analgesic. Paracetamol is a safe analgesic at recommended doses by the doctor.




Nonsteroidal anti-inflammatory drugs (usually abbreviated to NSAIDs), are drugs that decrease pain and lower fever. In higher doses, it decreases inflammation also. The most prominent members of this group of drugs are aspirin, ibuprofen, and naproxen.

COX-2 inhibitors

These drugs have been derived from NSAIDs. The cyclooxygenase enzyme inhibited by NSAIDs has two forms; COX1 and COX2. The analgesic effects are mediated by the COX2 (inducible) enzyme. Cyclooxygenase-2 (COX2), the enzyme acts to speed up the production of certain chemical messengers, called prostaglandins that play a key role in promoting inflammation. When COX-2 activity is blocked, inflammation is reduced. Thus, the COX2 inhibitors were developed to inhibit only the COX2 enzyme. These drugs (such as rofecoxib, celecoxib, and etoricoxib) are equally effective analgesics when compared with NSAIDs, and cause less gastrointestinal haemorrhage.

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Morphine is an exemplary opioid. The other opioids are codeine, oxycodone, hydrocodone, dihydromorphine, pethidine) all exert a similar influence on the cerebral opioid receptor system. Certain side effects of opioids toxicity are confusion, respiratory depression, myoclonic jerks and pinpoint pupils, seizures (tramadol), but opioid-tolerant individuals usually have higher dose limits than patients without tolerance. Patients starting morphine may experience nausea and vomiting. Constipation occurs in almost all patients on opioids, and laxatives (lactulose, macrogol-containing or co-danthramer) are typically co-prescribed.


Alcohol has biological, mental, and social effects which influence the consequences. Moderate use of alcohol can lessen certain types of pain in certain circumstances. Use alcohol to treat pain, again and again, has also been observed to lead to negative outcomes including excessive drinking and alcohol use disorder.

Medical cannabis

Cannabis can be evidently used to treat chronic pain and muscle spasms. Trials are being done, indicating improved relief of neuropathic pain over opioids.


Analgesic combination products contain either one or more types of analgesics with other medicines. The different analgesics generally have different modes of action and work simultaneously to reduce pain.

The use of paracetamol, aspirin, ibuprofen, naproxen, and other NSAIDs along with weak to mid-range opiates (up to about the hydrocodone level) has shown beneficial synergistic effects by combatting pain at multiple sites of action. These combination analgesics can be used in significant adverse events, including accidental overdoses, especially due to the confusion that arises from the multiple (and often non-acting) components of these combinations.

What are Analgesics and its Classification? NCERT Chemistry Class 12

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