Introduction: Autacoids are locally produced bioactive mediators — such as histamine, serotonin (5‑HT), prostaglandins, leukotrienes, bradykinin and nitric oxide — that regulate vascular tone, inflammation, pain, allergy and homeostasis. For B. Pharm students, understanding autacoid synthesis, receptor subtypes (H1–H4, 5‑HT families, prostanoid and leukotriene receptors), metabolic pathways (MAO, COMT, DAO, 5‑LOX, COX) and clinically relevant drugs (antihistamines, NSAIDs, triptans, leukotriene modifiers, ACE inhibitors) is essential for rational therapeutics and anticipating adverse effects and drug interactions. This concise, focused review prepares you for exam scenarios and clinical problem solving. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What best defines an autacoid?
- A circulating endocrine hormone acting on distant organs
- A locally produced endogenous mediator acting near its synthesis site
- A synthetic drug mimicking neurotransmitters
- An intracellular second messenger
Correct Answer: (A locally produced endogenous mediator acting near its synthesis site)
Q2. Which enzyme catalyzes the rate‑limiting step in serotonin synthesis?
- Monoamine oxidase (MAO)
- Trypsin
- Tryptophan hydroxylase
- Adenylate cyclase
Correct Answer: (Tryptophan hydroxylase)
Q3. Which histamine receptor primarily mediates gastric acid secretion?
- H1
- H2
- H3
- H4
Correct Answer: (H2)
Q4. Which enzyme converts arachidonic acid to prostaglandin endoperoxides (PGG2/PGH2)?
- 5‑lipoxygenase (5‑LOX)
- Cyclooxygenase (COX)
- Prostacyclin synthase
- Thromboxane synthase
Correct Answer: (Cyclooxygenase (COX))
Q5. Which prostaglandin is most associated with fever and sensitization of pain receptors?
- PGF2α
- PGE2
- PGI2 (prostacyclin)
- TXA2
Correct Answer: (PGE2)
Q6. Leukotriene receptor antagonists like montelukast primarily block which receptor?
- LTB4 receptor
- CysLT1 receptor
- 5‑HT3 receptor
- H1 receptor
Correct Answer: (CysLT1 receptor)
Q7. Which autacoid commonly causes bronchoconstriction, increased vascular permeability, and pruritus in allergic reactions?
- Bradykinin
- Histamine
- Prostacyclin
- Nitric oxide
Correct Answer: (Histamine)
Q8. Which drug class reduces prostaglandin synthesis by inhibiting COX and is frequently used for pain and inflammation?
- Selective serotonin reuptake inhibitors (SSRIs)
- NSAIDs
- Leukotriene receptor antagonists
- ACE inhibitors
Correct Answer: (NSAIDs)
Q9. Which histamine receptor functions mainly as an autoreceptor in the CNS to inhibit histamine release?
- H1
- H2
- H3
- H4
Correct Answer: (H3)
Q10. 5‑HT3 receptor antagonists (e.g., ondansetron) are clinically used for which indication?
- Asthma prophylaxis
- Antiemetic therapy for chemotherapy‑induced nausea
- Antiplatelet therapy
- Prostaglandin synthesis inhibition
Correct Answer: (Antiemetic therapy for chemotherapy‑induced nausea)
Q11. Which enzyme primarily metabolizes serotonin into 5‑HIAA?
- Monoamine oxidase (MAO)
- Histamine N‑methyltransferase (HNMT)
- Diamine oxidase (DAO)
- 5‑lipoxygenase (5‑LOX)
Correct Answer: (Monoamine oxidase (MAO))
Q12. Which prostaglandin inhibits platelet aggregation and causes vasodilation?
- TXA2
- PGE2
- PGI2 (prostacyclin)
- PGF2α
Correct Answer: (PGI2 (prostacyclin))
Q13. Zileuton produces its therapeutic effect by inhibiting which enzyme?
- COX‑2
- 5‑lipoxygenase (5‑LOX)
- Phospholipase C
- Histidine decarboxylase
Correct Answer: (5‑lipoxygenase (5‑LOX))
Q14. ACE inhibitors can cause cough due to accumulation of which autacoid?
- Prostaglandins
- Bradykinin
- Serotonin
- Thromboxane
Correct Answer: (Bradykinin)
Q15. Which histamine receptor antagonists are most likely to cause sedation due to central H1 blockade?
- Second‑generation H1 antagonists (loratadine)
- First‑generation H1 antagonists (diphenhydramine)
- H2 antagonists (ranitidine)
- H3 antagonists
Correct Answer: (First‑generation H1 antagonists (diphenhydramine))
Q16. Which autacoid is synthesized by nitric oxide synthase from L‑arginine and mediates vasodilation via cGMP?
- Nitric oxide
- Prostaglandin E2
- Histamine
- Leukotriene C4
Correct Answer: (Nitric oxide)
Q17. Triptans relieve migraine primarily through agonism at which receptors?
- 5‑HT1B/1D receptors causing cranial vasoconstriction
- 5‑HT3 receptors causing antiemesis
- H1 receptors reducing inflammation
- Beta‑adrenergic receptors lowering blood pressure
Correct Answer: (5‑HT1B/1D receptors causing cranial vasoconstriction)
Q18. Which pathway produces leukotrienes from membrane phospholipids?
- COX pathway
- 5‑LOX pathway
- MAO pathway
- COMT pathway
Correct Answer: (5‑LOX pathway)
Q19. Histamine metabolism in the gut primarily involves which enzyme?
- Monoamine oxidase (MAO)
- Histamine N‑methyltransferase (HNMT)
- Diamine oxidase (DAO)
- Cyclooxygenase (COX)
Correct Answer: (Diamine oxidase (DAO))
Q20. Which adverse effect is particularly associated with COX‑2 selective inhibitors compared with nonselective NSAIDs?
- Increased gastrointestinal bleeding
- Decreased renal blood flow only
- Increased cardiovascular thrombotic risk
- Excessive sedation
Correct Answer: (Increased cardiovascular thrombotic risk)
Q21. Which autacoid is a potent chemoattractant for neutrophils generated from arachidonic acid?
- LTC4
- LXB4 and LTB4
- PGE2
- PGI2
Correct Answer: (LXB4 and LTB4)
Q22. Serotonin syndrome results from excess serotonergic activity; which drug combination increases this risk?
- SSRI plus MAO inhibitor
- NSAID plus acetaminophen
- Antihistamine plus decongestant
- ACE inhibitor plus thiazide diuretic
Correct Answer: (SSRI plus MAO inhibitor)
Q23. Misoprostol is a synthetic analogue of which prostaglandin used to protect gastric mucosa?
- PGE1 analogue
- PGF2α analogue
- PGD2 analogue
- TXA2 analogue
Correct Answer: (PGE1 analogue)
Q24. Which receptor subtype mediates itch, vasodilation and increased vascular permeability when activated by histamine?
- H2 receptor
- H1 receptor
- H3 receptor
- H4 receptor
Correct Answer: (H1 receptor)
Q25. Which statement about prostaglandin synthesis is true?
- COX converts leukotrienes into prostaglandins
- Phospholipase A2 releases arachidonic acid from membrane phospholipids
- Prostaglandins are synthesized only in the liver
- Thromboxane synthase is responsible for PGE2 formation
Correct Answer: (Phospholipase A2 releases arachidonic acid from membrane phospholipids)
Q26. Which leukotriene is most implicated in bronchoconstriction in asthma?
- LTB4
- LTC4/LTD4
- LXA4
- PGE2
Correct Answer: (LTC4/LTD4)
Q27. H2 receptor antagonists such as cimetidine can cause which drug interaction due to CYP inhibition?
- Increased metabolism of warfarin
- Reduced levels of benzodiazepines
- Inhibition of cytochrome P450 leading to increased plasma levels of some drugs
- Induction of CYP leading to lower drug levels
Correct Answer: (Inhibition of cytochrome P450 leading to increased plasma levels of some drugs)
Q28. Which autacoid directly activates guanylate cyclase in vascular smooth muscle to increase cGMP?
- Bradykinin
- Nitric oxide
- Thromboxane A2
- Leukotriene B4
Correct Answer: (Nitric oxide)
Q29. Which clinical effect is most characteristic of thromboxane A2 (TXA2)?
- Vasodilation and inhibition of platelet aggregation
- Bronchodilation and antiinflammatory action
- Platelet aggregation and vasoconstriction
- Analgesia and fever reduction
Correct Answer: (Platelet aggregation and vasoconstriction)
Q30. Which pharmacologic approach is appropriate for preventing leukotriene‑mediated asthma exacerbations?
- H2 receptor antagonists
- Leukotriene receptor antagonists (e.g., montelukast) or 5‑LOX inhibitors (e.g., zileuton)
- Proton pump inhibitors
- Beta‑lactam antibiotics
Correct Answer: (Leukotriene receptor antagonists (e.g., montelukast) or 5‑LOX inhibitors (e.g., zileuton))
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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