Alkaloids – Opium are a vital topic for B.Pharm students, covering chemistry, pharmacology, toxicology and therapeutic uses of opium-derived compounds such as morphine, codeine and thebaine. This introduction highlights biosynthesis, structural features, receptor interactions, metabolism (UGT and CYP pathways), analytical assays (TLC, HPLC), clinical applications (analgesia, antitussive, antidiarrheal) and public health concerns including tolerance, dependence and regulatory control. Understanding structure–activity relationships, key derivatives (heroin, oxycodone, buprenorphine), and identification tests is essential for pharmacists involved in therapeutics, formulation and forensic analysis. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which three alkaloids are considered the major constituents of opium?
- Morphine, Codeine, Thebaine
- Morphine, Papaverine, Strychnine
- Codeine, Nicotine, Quinine
- Thebaine, Atropine, Cocaine
Correct Answer: Morphine, Codeine, Thebaine
Q2. Morphine belongs to which class of alkaloids based on its core structure?
- Phenanthrene alkaloids
- Indole alkaloids
- Quinoline alkaloids
Correct Answer: Phenanthrene alkaloids
Q3. Which biosynthetic intermediate is a key precursor in the formation of morphinan alkaloids like morphine?
- (S)-Reticuline
- L-Tryptophan
- Nicotine
- Lysine
Correct Answer: (S)-Reticuline
Q4. The analgesic activity of morphine is mainly attributed to which functional group at C-3?
- Phenolic hydroxyl group
- Allylic double bond
- Secondary amine
- Acetyl ester
Correct Answer: Phenolic hydroxyl group
Q5. Codeine differs from morphine primarily by which structural modification?
- O-methylation of the 3-hydroxyl group
- Hydrogenation of the aromatic ring
- Acetylation of both 3- and 6-hydroxyl groups
- Removal of the tertiary amine
Correct Answer: O-methylation of the 3-hydroxyl group
Q6. Which opium alkaloid is most commonly used as the chemical precursor for semisynthetic opioids like oxycodone?
- Thebaine
- Morphine
- Codeine
- Papaverine
Correct Answer: Thebaine
Q7. Which reagent is classically used to give a characteristic precipitate with many alkaloids in qualitative tests?
- Dragendorff reagent
- Biuret reagent
- KMnO4 reagent
- Ninhydrin reagent
Correct Answer: Dragendorff reagent
Q8. Morphine primarily exerts its analgesic effect through agonism at which receptor?
- Mu-opioid receptor
- Alpha-2 adrenergic receptor
- NMDA receptor
- GABA-A receptor
Correct Answer: Mu-opioid receptor
Q9. Naloxone is best described pharmacologically as which of the following?
- Competitive mu-opioid receptor antagonist
- Noncompetitive NMDA antagonist
- Partial mu-opioid receptor agonist
- Peripheral kappa agonist
Correct Answer: Competitive mu-opioid receptor antagonist
Q10. Which morphine metabolite is known to be pharmacologically active and contributes to analgesia?
- Morphine-6-glucuronide (M6G)
- Morphine-3-sulfate
- Normorphine
- Codeine-6-glucuronide
Correct Answer: Morphine-6-glucuronide (M6G)
Q11. What is the typical elimination half-life range of morphine after intravenous administration in adults?
- Approximately 2–4 hours
- Approximately 8–12 hours
- 30–60 minutes
- 24–48 hours
Correct Answer: Approximately 2–4 hours
Q12. Conversion of codeine to morphine in the body is primarily mediated by which cytochrome P450 enzyme?
- CYP2D6
- CYP3A4
- CYP1A2
- CYP2C19
Correct Answer: CYP2D6
Q13. Why does heroin (diacetylmorphine) produce a faster onset of central effects compared with morphine?
- Increased lipophilicity due to acetylation allows faster blood–brain barrier penetration
- It is a stronger mu receptor agonist by molecular structure alone
- It is not metabolized in the liver
- It directly stimulates GABA release
Correct Answer: Increased lipophilicity due to acetylation allows faster blood–brain barrier penetration
Q14. Nalbuphine is best classified pharmacologically as which of the following?
- Kappa opioid receptor agonist and mu opioid receptor antagonist
- Pure mu opioid receptor agonist
- Nonselective monoamine reuptake inhibitor
- NMDA receptor antagonist
Correct Answer: Kappa opioid receptor agonist and mu opioid receptor antagonist
Q15. The life-threatening adverse effect of opioids, respiratory depression, is primarily mediated via which mechanism?
- Activation of mu-opioid receptors in the brainstem respiratory centers
- Peripheral vasodilation leading to hypoxia
- Inhibition of acetylcholinesterase
- Excessive histamine release causing airway constriction
Correct Answer: Activation of mu-opioid receptors in the brainstem respiratory centers
Q16. Which opiate is commonly used as an antitussive at low doses?
- Codeine
- Buprenorphine
- Morphine sulfate (parenteral)
- Nalbuphine
Correct Answer: Codeine
Q17. Which of the following opioid effects on the gastrointestinal tract is most clinically significant and persistent?
- Constipation due to decreased enteric motility
- Diarrhea due to secretory stimulation
- Enhanced gastric acid secretion leading to ulcers
- Increased bile secretion
Correct Answer: Constipation due to decreased enteric motility
Q18. Which qualitative chemical test gives a positive color reaction with morphine because of its free phenolic group?
- Ferric chloride test
- Fehling’s test
- Biuret test
- Molisch test
Correct Answer: Ferric chloride test
Q19. Which enzyme family catalyzes glucuronidation of morphine to form morphine glucuronides?
- UDP-glucuronosyltransferases (UGTs), primarily UGT2B7
- CYP450 monooxygenases, primarily CYP2E1
- Glutathione S-transferases (GSTs)
- Aldehyde dehydrogenases (ALDH)
Correct Answer: UDP-glucuronosyltransferases (UGTs), primarily UGT2B7
Q20. Which salt form of morphine is widely used for parenteral preparations?
- Morphine sulfate
- Morphine hydrochloride
- Morphine citrate
- Morphine phosphate
Correct Answer: Morphine sulfate
Q21. Oxycodone is semisynthetically derived from which natural opium alkaloid?
- Thebaine
- Morphine
- Codeine
- Papaverine
Correct Answer: Thebaine
Q22. A major cellular mechanism contributing to opioid tolerance is:
- Receptor desensitization and internalization
- Increased renal excretion of drug unchanged
- Upregulation of opioid peptide synthesis
- Permanent mutation of the mu receptor gene
Correct Answer: Receptor desensitization and internalization
Q23. Which opioid is commonly used in maintenance therapy for opioid dependence due to its long duration of action?
- Methadone
- Fentanyl
- Heroin
- Naloxone
Correct Answer: Methadone
Q24. Which opioid acts as a high-affinity partial agonist at the mu receptor and is used in opioid dependence treatment?
- Buprenorphine
- Codeine
- Morphine
- Nalbuphine
Correct Answer: Buprenorphine
Q25. Conversion of morphine to heroin is achieved by which chemical reaction?
- Acetylation of the 3- and 6-hydroxyl groups (diacetylation)
- Methylation of the phenolic hydroxyl at C-3
- Oxidative cleavage of the piperidine ring
- Hydrogenation of the aromatic system
Correct Answer: Acetylation of the 3- and 6-hydroxyl groups (diacetylation)
Q26. Which opioid is primarily used as an antidiarrheal and has poor central nervous system penetration?
- Loperamide
- Morphine
- Codeine
- Fentanyl
Correct Answer: Loperamide
Q27. For quantitative determination of morphine in pharmaceutical samples, which analytical technique is most commonly employed?
- High-performance liquid chromatography (HPLC)
- Paper chromatography
- Classical colorimetry only
- Simple gravimetric analysis
Correct Answer: High-performance liquid chromatography (HPLC)
Q28. Opioid-induced constipation is primarily due to which of the following?
- Activation of enteric mu-opioid receptors decreasing gut motility
- Stimulation of intestinal secretions
- Competitive antagonism at serotonin receptors
- Induction of pancreatic enzyme secretion
Correct Answer: Activation of enteric mu-opioid receptors decreasing gut motility
Q29. A patient who is a CYP2D6 poor metabolizer will likely experience which effect when given codeine for analgesia?
- Reduced analgesic effect due to less conversion to morphine
- Enhanced toxicity due to accumulation of codeine
- Increased conversion to morphine causing respiratory depression
- No change in analgesic response
Correct Answer: Reduced analgesic effect due to less conversion to morphine
Q30. Which opium alkaloid is known for causing central stimulant and convulsant effects rather than typical opioid sedation at high doses?
- Thebaine
- Morphine
- Codeine
- Papaverine
Correct Answer: Thebaine
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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