Orris

Autacoids and Related Drugs: Nonsteroidal, Anti-inflammatory (NSAIDs)/Antipyretic and Analgesics Drugs Explain in easy language as per Dravya Guna ncism syllabus

Reading File
Finding Sources
Finding Sources

Autacoids & NSAIDs/Antipyretic-Analgesics — Topic Map

This is a fairly large chapter in the BAMS/NCISM modern pharmacology syllabus (usually clubbed under "Autacoids and Related Drugs"). Here's how it typically breaks down:
  1. Introduction to Autacoids - definition ("local hormones"), classification (histamine, serotonin, eicosanoids, kinins, PAF)
  2. Histamine & Antihistamines - H1/H2/H3/H4 receptors, actions, antihistamine drug classes
  3. Serotonin (5-HT) - receptor subtypes, physiological roles, agonists/antagonists (e.g., sumatriptan, ondansetron)
  4. Eicosanoids - Prostaglandins, Thromboxane, Leukotrienes - synthesis pathway (arachidonic acid, COX/LOX), physiological actions
  5. Kinins & PAF - bradykinin, platelet activating factor, clinical relevance
  6. NSAIDs - Classification & Mechanism - COX-1 vs COX-2 inhibition, non-selective vs selective agents
  7. Individual NSAIDs - Aspirin, Diclofenac, Ibuprofen, Indomethacin, Naproxen, Mefenamic acid, Piroxicam - uses, dose, adverse effects
  8. Selective COX-2 Inhibitors - Celecoxib, Etoricoxib - rationale, cardiovascular risk
  9. Antipyretic-Analgesics - Paracetamol (Acetaminophen) - mechanism, uses, hepatotoxicity/overdose management
  10. Adverse Effects of NSAIDs - GI ulceration, nephrotoxicity, cardiovascular risk, drug interactions, Reye's syndrome (aspirin in children)
Quick overview: Autacoids are endogenous, locally-acting chemical mediators (unlike hormones which act at a distance) - they include histamine, serotonin, prostaglandins/leukotrienes, bradykinin, and PAF, and they mediate inflammation, pain, fever, allergy, and vascular responses. NSAIDs work mainly by inhibiting the cyclooxygenase (COX) enzyme, blocking prostaglandin synthesis - this gives them anti-inflammatory, analgesic, and antipyretic effects, but also causes their main side effects (gastric irritation via loss of protective PGE2, renal effects via reduced renal PGs). Paracetamol is grouped with this class for its antipyretic/analgesic action but has weak anti-inflammatory effect and works more centrally, with a distinct toxicity profile (liver damage in overdose) rather than GI/renal toxicity.
Which topic would you like explained in full detail first?
Asking for Preferences

Which part of this chapter should I explain in detail first?

Autacoids & NSAIDs/Antipyretic-Analgesics — Topic Map

This is a fairly large chapter in the BAMS/NCISM modern pharmacology syllabus (usually clubbed under "Autacoids and Related Drugs"). Here's how it typically breaks down:
  1. Introduction to Autacoids - definition ("local hormones"), classification (histamine, serotonin, eicosanoids, kinins, PAF)
  2. Histamine & Antihistamines - H1/H2/H3/H4 receptors, actions, antihistamine drug classes
  3. Serotonin (5-HT) - receptor subtypes, physiological roles, agonists/antagonists (e.g., sumatriptan, ondansetron)
  4. Eicosanoids - Prostaglandins, Thromboxane, Leukotrienes - synthesis pathway (arachidonic acid, COX/LOX), physiological actions
  5. Kinins & PAF - bradykinin, platelet activating factor, clinical relevance
  6. NSAIDs - Classification & Mechanism - COX-1 vs COX-2 inhibition, non-selective vs selective agents
  7. Individual NSAIDs - Aspirin, Diclofenac, Ibuprofen, Indomethacin, Naproxen, Mefenamic acid, Piroxicam - uses, dose, adverse effects
  8. Selective COX-2 Inhibitors - Celecoxib, Etoricoxib - rationale, cardiovascular risk
  9. Antipyretic-Analgesics - Paracetamol (Acetaminophen) - mechanism, uses, hepatotoxicity/overdose management
  10. Adverse Effects of NSAIDs - GI ulceration, nephrotoxicity, cardiovascular risk, drug interactions, Reye's syndrome (aspirin in children)
Quick overview: Autacoids are endogenous, locally-acting chemical mediators (unlike hormones which act at a distance) - they include histamine, serotonin, prostaglandins/leukotrienes, bradykinin, and PAF, and they mediate inflammation, pain, fever, allergy, and vascular responses. NSAIDs work mainly by inhibiting the cyclooxygenase (COX) enzyme, blocking prostaglandin synthesis - this gives them anti-inflammatory, analgesic, and antipyretic effects, but also causes their main side effects (gastric irritation via loss of protective PGE2, renal effects via reduced renal PGs). Paracetamol is grouped with this class for its antipyretic/analgesic action but has weak anti-inflammatory effect and works more centrally, with a distinct toxicity profile (liver damage in overdose) rather than GI/renal toxicity.
Which topic would you like explained in full detail first?
Finding Sources
Finding Sources
Finding Sources
Finding Sources

Autacoids and NSAIDs / Antipyretic-Analgesic Drugs — Easy Notes

1. What are Autacoids?

Autacoids (from Greek autos = self, akos = remedy) are substances made by the body itself that act locally, near the place they are released, unlike hormones which travel in blood to distant organs. They are sometimes called "local hormones."
Main groups of Autacoids:
  • Histamine
  • Serotonin (5-HT)
  • Eicosanoids - Prostaglandins, Thromboxanes, Leukotrienes (made from arachidonic acid)
  • Kinins (Bradykinin)
  • Platelet Activating Factor (PAF)
For this chapter, the important group is the Eicosanoids, because NSAIDs act directly on this pathway.

2. Eicosanoid Pathway — the Key to Understanding NSAIDs

When cell membranes are damaged (injury, infection, inflammation), an enzyme called phospholipase A2 releases arachidonic acid from membrane phospholipids. This arachidonic acid can go down two paths:
  • Cyclooxygenase (COX) pathway → makes Prostaglandins (PGE2, PGF2α), Prostacyclin (PGI2), Thromboxane A2
  • Lipoxygenase (LOX) pathway → makes Leukotrienes (important in asthma/allergy, not the focus of NSAIDs)
Two forms of COX enzyme - this is the single most important concept for NSAIDs:
COX-1COX-2
Nature"Housekeeping" enzyme, present normally in most tissues"Inducible" enzyme, appears mainly during inflammation
FunctionProtects stomach lining, maintains kidney blood flow, helps platelet aggregation (via thromboxane)Produces prostaglandins that cause pain, fever, and inflammation
Effect of blocking itCauses the side effects of NSAIDs (gastric ulcers, bleeding, renal problems)Blocking it gives the desired anti-inflammatory/analgesic effect
As one textbook explains: "Cyclooxygenase-1 (COX-1) is responsible for the physiologic production of prostanoids, whereas cyclooxygenase-2 (COX-2) causes the elevated production of prostanoids that occurs in sites of disease and inflammation" - Lippincott Illustrated Reviews: Pharmacology.
This is why drug design moved from non-selective NSAIDs (block both COX-1 and COX-2) toward selective COX-2 inhibitors (block mainly COX-2, sparing the stomach-protecting COX-1).

3. NSAIDs — Classification

A. Non-selective COX inhibitors (block both COX-1 and COX-2):
  • Salicylates: Aspirin
  • Propionic acid derivatives: Ibuprofen, Naproxen, Ketoprofen
  • Acetic acid derivatives: Diclofenac, Indomethacin
  • Fenamates: Mefenamic acid
  • Oxicams: Piroxicam
  • Pyrazolones: Phenylbutazone
B. Preferential/Selective COX-2 inhibitors:
  • Preferential: Nimesulide, Meloxicam
  • Highly selective (Coxibs): Celecoxib, Etoricoxib, Parecoxib
C. Para-aminophenol derivative (antipyretic-analgesic, weak anti-inflammatory):
  • Paracetamol (Acetaminophen)
General actions of NSAIDs (the "3 A's"):
  1. Anti-inflammatory - reduces swelling, redness, pain of inflammation by blocking PG synthesis
  2. Analgesic - relieves mild-to-moderate pain, especially pain from inflammation (dental pain, headache, muscle pain, arthritis)
  3. Antipyretic - lowers raised body temperature by blocking PGE2 synthesis in the hypothalamus (PGE2 normally raises the body's temperature "set point" during fever)
Aspirin has an extra property at low dose: it irreversibly inhibits COX-1 in platelets, reducing thromboxane A2 and giving an antiplatelet effect - hence its use in preventing heart attacks/stroke.

4. Individual Drugs (short profile)

  • Aspirin (Acetylsalicylic acid): Oldest NSAID, irreversible COX inhibitor. Uses: mild pain, fever, low-dose for cardioprotection. Side effects: gastric ulcer/bleeding, tinnitus at high dose, and importantly - must be avoided in children/adolescents with viral fever because of the risk of Reye's syndrome, a rare but often fatal condition with liver failure and brain swelling. As Goodman & Gilman's states: "aspirin and other salicylates are contraindicated in children and young adults less than 20 years of age with viral illness-associated fever" due to this link.
  • Ibuprofen: Widely used, relatively safer GI profile than aspirin/indomethacin, common OTC analgesic-antipyretic.
  • Diclofenac: Potent anti-inflammatory, commonly used in musculoskeletal pain, available as gel/tablet/injection.
  • Indomethacin: Very potent but higher GI/CNS side effects, used in acute gout, ankylosing spondylitis.
  • Mefenamic acid: Used in dysmenorrhea, mild pain.
  • Piroxicam: Long half-life, once-daily dosing, used in chronic arthritis.
  • Celecoxib/Etoricoxib: Selective COX-2 inhibitors, less GI toxicity but carry increased cardiovascular risk (thrombosis) since they don't inhibit platelet thromboxane.

5. Antipyretic Analgesic — Paracetamol (Acetaminophen)

Paracetamol is grouped with NSAIDs functionally but is chemically different (para-aminophenol derivative):
  • Mechanism: Weak peripheral COX inhibition (so weak anti-inflammatory action) but effective central antipyretic/analgesic action, possibly through central COX inhibition and other central pathways.
  • Uses: Fever, mild-to-moderate pain - safe in children, safe in patients where NSAIDs are contraindicated (peptic ulcer, asthma, pregnancy in normal dose).
  • Advantage over NSAIDs: No significant GI ulceration, no antiplatelet effect, no Reye's syndrome risk.
  • Major danger - Overdose Hepatotoxicity: In overdose, the normal metabolic pathway gets saturated, and paracetamol is converted by CYP450 enzymes into a toxic metabolite (NAPQI) that depletes liver glutathione and causes severe liver necrosis, which can be fatal. As one textbook notes: "In normal doses, acetaminophen is safe and effective, but it may cause severe hepatic toxicity or death when consumed in overdose quantities" - Tietz Textbook of Laboratory Medicine. Antidote for overdose: N-acetylcysteine (replenishes glutathione).

6. Adverse Effects of NSAIDs (as a class) — Easy Recall

  • GI: Gastritis, peptic ulcer, GI bleeding (due to loss of protective PGE2/PGI2 in stomach mucosa)
  • Renal: Reduced renal blood flow, sodium/water retention, risk of acute kidney injury (especially in elderly, dehydrated, or with pre-existing kidney disease) - because renal PGs maintain blood flow to the kidney
  • Cardiovascular: Selective COX-2 inhibitors can increase risk of heart attack/stroke due to unopposed thromboxane effect
  • Hypersensitivity: Aspirin-induced asthma/bronchospasm in sensitive patients
  • Aspirin specific: Reye's syndrome in children with viral fever

Quick Comparison Table

FeatureNon-selective NSAIDsSelective COX-2 inhibitorsParacetamol
Anti-inflammatoryStrongStrongWeak
AnalgesicYesYesYes
AntipyreticYesYesYes
GI toxicityHighLowVery low
CV riskLow (aspirin protective)IncreasedMinimal
Major toxicityGI ulcer/bleedThrombosisLiver damage in overdose
If you want, I can go deeper into any single area - for example, detailed mechanism diagrams of the COX pathway, or a dedicated note on Reye's syndrome / paracetamol overdose management - just let me know which one.
This is a shared conversation. Sign in to Orris to start your own chat.