Alkaloids – Caffeine MCQs With Answer

Alkaloids – Caffeine MCQs With Answer

Caffeine is a prominent plant alkaloid and a methylxanthine stimulant with wide relevance in pharmacology, pharmacokinetics, analytical chemistry, toxicology and pharmacy practice. This concise introduction reviews caffeine’s chemical structure, biosynthesis, extraction, mechanism of action as an adenosine receptor antagonist, metabolic pathways (CYP1A2 demethylation), therapeutic uses (e.g., neonatal apnea), adverse effects, drug interactions and common analytical assays (HPLC, UV). Designed for B. Pharm students, these focused, exam-oriented MCQs reinforce core concepts about formulation, stability, dosing and regulatory aspects of caffeine in pharmaceuticals. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. What is the chemical class of caffeine?

• Methylxanthine alkaloid
• Isoquinoline alkaloid
• Tropane alkaloid
• Quinolone antibiotic

Correct Answer: Methylxanthine alkaloid

Q2. What is the IUPAC name of caffeine?

• 1,3,7-trimethylxanthine
• 3,7-dimethylxanthine
• 1,3-dimethylpurine
• 7-methyladenosine

Correct Answer: 1,3,7-trimethylxanthine

Q3. What is the molecular formula of caffeine?

• C8H10N4O2
• C7H8N4O2
• C9H12N4O3
• C10H12N2O2

Correct Answer: C8H10N4O2

Q4. Which plant biosynthetic precursor is most directly involved in caffeine formation?

• Xanthosine
• Tryptophan
• Tyrosine
• Ornithine

Correct Answer: Xanthosine

Q5. Which receptor is primarily antagonized by caffeine to produce central stimulation?

• Adenosine receptors (A1 and A2A)
• Dopamine D2 receptors
• GABA-A receptors
• Serotonin 5-HT2A receptors

Correct Answer: Adenosine receptors (A1 and A2A)

Q6. The major hepatic metabolite of caffeine formed by CYP1A2 in humans is:

• Paraxanthine
• Theobromine
• Theophylline
• Uric acid

Correct Answer: Paraxanthine

Q7. Which clinical indication is caffeine citrate officially used for?

• Neonatal apnea
• Hypertension
• Parkinson’s disease
• Type 2 diabetes

Correct Answer: Neonatal apnea

Q8. Typical oral half-life of caffeine in healthy adults is approximately:

• 3–7 hours
• 0.5–1 hour
• 24–48 hours
• 12–18 hours

Correct Answer: 3–7 hours

Q9. Which analytical technique is considered most specific and widely used for quantitative determination of caffeine in pharmaceutical and biological samples?

• High-performance liquid chromatography (HPLC)
• Paper chromatography
• Flame photometry
• Nitrogen balance assay

Correct Answer: High-performance liquid chromatography (HPLC)

Q10. Which of the following methylxanthines is primarily used as an oral bronchodilator?

• Theophylline
Theobromine
• Caffeine citrate
• Paraxanthine

Correct Answer: Theophylline

Q11. Caffeine’s bitter taste is mainly due to which chemical property?

• Basic heterocyclic structure interacting with taste receptors
• High sugar content
• Presence of fatty acid esters
• Metal ion contamination

Correct Answer: Basic heterocyclic structure interacting with taste receptors

Q12. Which lifestyle factor significantly decreases caffeine plasma half-life by inducing CYP1A2?

• Smoking
• Grapefruit juice consumption
• Vegetarian diet
• Regular exercise

Correct Answer: Smoking

Q13. Which adverse effect is most commonly associated with moderate caffeine consumption?

• Insomnia and nervousness
• Severe hypoglycemia
• Hepatic necrosis
• Renal failure

Correct Answer: Insomnia and nervousness

Q14. Which statement about caffeine pharmacokinetics is correct?

• Caffeine is rapidly and completely absorbed after oral administration
• Caffeine is poorly absorbed orally and requires IV dosing
• Caffeine accumulates extensively in adipose tissue
• Caffeine is excreted unchanged primarily in bile

Correct Answer: Caffeine is rapidly and completely absorbed after oral administration

Q15. In analytical UV spectroscopy, caffeine shows a characteristic absorption maximum near which wavelength?

• 272 nm
• 520 nm
• 350 nm
• 620 nm

Correct Answer: 272 nm

Q16. Which extraction solvent is commonly used for isolating caffeine from plant material in laboratory protocols?

• Chloroform or dichloromethane
• Hexane
• Petroleum jelly
• Isopropyl alcohol with low polarity

Correct Answer: Chloroform or dichloromethane

Q17. Which population is particularly advised to limit caffeine intake due to slower metabolism and fetal exposure?

• Pregnant women
• Adolescent males
• Postmenopausal women on HRT
• Young athletes

Correct Answer: Pregnant women

Q18. The primary route of elimination for caffeine and its metabolites is:

• Renal excretion
• Exhalation via lungs
• Fecal elimination unchanged
• Transdermal loss

Correct Answer: Renal excretion

Q19. Which statement about caffeine’s stereochemistry is correct?

• Caffeine is an achiral molecule
• Caffeine has one stereocenter
• Caffeine exists as two enantiomers used pharmaceutically
• Caffeine is a racemic mixture of diastereomers

Correct Answer: Caffeine is an achiral molecule

Q20. Which drug interaction can increase plasma caffeine levels by inhibiting CYP1A2?

• Fluvoxamine (CYP1A2 inhibitor)
• Rifampicin (CYP inducer)
• Carbamazepine (CYP inducer)
• Smoking tobacco (CYP inducer)

Correct Answer: Fluvoxamine (CYP1A2 inhibitor)

Q21. Which toxic effect may occur with acute caffeine overdose?

• Seizures and severe tachyarrhythmias
• Progressive muscle hypertrophy
• Hypothermia and bradycardia
• Pancreatic insufficiency

Correct Answer: Seizures and severe tachyarrhythmias

Q22. Which methylxanthine is found predominantly in cocoa and contributes more to its effects than caffeine?

• Theobromine
• Paraxanthine
• Theophylline
• Hypoxanthine

Correct Answer: Theobromine

Q23. For pharmaceutical formulations, caffeine citrate is preferred because:

• It is more water-soluble and suitable for IV/PO neonatal use
• It is lipid-soluble for topical application
• It is an esterified prodrug active only after liver metabolism
• It has lower potency than caffeine base

Correct Answer: It is more water-soluble and suitable for IV/PO neonatal use

Q24. Which regulatory classification best describes caffeine in most jurisdictions?

• Non-controlled stimulant available in foods and OTC products
• Schedule I controlled substance
• Prescription-only opioid agonist
• Banned anabolic agent

Correct Answer: Non-controlled stimulant available in foods and OTC products

Q25. Which structural feature defines caffeine as a xanthine derivative?

• Purine-like fused imidazole and pyrimidine rings with carbonyl groups
• Tropane bicyclic ring system
• Indole nucleus with an attached benzene ring
• Steroidal tetracyclic nucleus

Correct Answer: Purine-like fused imidazole and pyrimidine rings with carbonyl groups

Q26. In therapeutic drug monitoring or forensic analysis, which biological matrix is most commonly analyzed for caffeine levels?

• Plasma/serum
• Synovial fluid
• Sweat
• Hair exclusively

Correct Answer: Plasma/serum

Q27. Industrially, pharmaceutical-grade caffeine is frequently obtained by:

• Chemical synthesis rather than exclusively from plant extraction
• Fermentation of glucose by yeast
• Isolation from human saliva
• Electrochemical deposition

Correct Answer: Chemical synthesis rather than exclusively from plant extraction

Q28. Which pharmacodynamic action contributes to caffeine’s diuretic effect?

• Renal adenosine receptor antagonism increasing renal blood flow and GFR
• Direct inhibition of angiotensin-converting enzyme
• Strong vasopressin agonism
• Inhibition of renal sodium-potassium ATPase exclusively

Correct Answer: Renal adenosine receptor antagonism increasing renal blood flow and GFR

Q29. Which analytical validation parameter is most critical when developing an HPLC method for caffeine quantification in tablets?

• Specificity/selectivity to separate caffeine from excipients and related impurities
• Taste masking efficiency
• Particle size distribution
• Thermal conductivity of the column hardware

Correct Answer: Specificity/selectivity to separate caffeine from excipients and related impurities

Q30. Blockade of which adenosine receptor subtype is most closely linked to caffeine’s wake-promoting effects?

• A2A receptor antagonism in the brain
• A3 receptor activation in peripheral tissues
• A1 receptor agonism only
• A2B receptor irreversible inhibition

Correct Answer: A2A receptor antagonism in the brain

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com