Structure and uses of hexamine MCQs With Answer

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Structure and uses of hexamine MCQs With Answer — Hexamine (hexamethylenetetramine or methenamine) is a cage-like heterocyclic amine (C6H12N4) widely studied in pharmaceutical chemistry for its unique tetrahedral nitrogen framework and role as a formaldehyde donor. For B. Pharm students, mastering its molecular structure, synthesis, physicochemical properties, mechanism of action and pharmaceutical uses — especially as urinary antiseptics (methenamine hippurate/mandelate) — is essential. These MCQs focus on structural features, acid-catalyzed decomposition to formaldehyde, therapeutic applications, contraindications, and industrial roles to deepen conceptual understanding and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following is the common pharmaceutical name for hexamethylenetetramine?

  • Urotropine
  • Imipramine
  • Proguanil
  • Chlordiazepoxide

Correct Answer: Urotropine

Q2. What is the empirical molecular formula of hexamine?

  • C6H6N4
  • C6H12N4
  • C5H10N2
  • CH2N2

Correct Answer: C6H12N4

Q3. The primary clinical use of methenamine salts in pharmacy is as:

  • Topical antifungal agents
  • Systemic antiviral drugs
  • Urinary antiseptics
  • Antihypertensive agents

Correct Answer: Urinary antiseptics

Q4. Hexamine releases which bactericidal agent under acidic conditions?

  • Formaldehyde
  • Hydrogen peroxide
  • Hypochlorous acid
  • Peracetic acid

Correct Answer: Formaldehyde

Q5. Methenamine hippurate is preferred over methenamine mandelate because it:

  • Requires basic urine for activation
  • Produces less formaldehyde
  • Provides lower urinary pH and prolonged action
  • Is more nephrotoxic

Correct Answer: Provides lower urinary pH and prolonged action

Q6. The three-dimensional structure of hexamine is best described as:

  • Linear chain of amines
  • Planar aromatic ring
  • Cage-like heterocyclic tetraamine
  • Spherical metal complex

Correct Answer: Cage-like heterocyclic tetraamine

Q7. Which functional groups are directly present in hexamine?

  • Primary amine groups
  • Secondary amide groups
  • Tertiary amine nitrogen atoms linked by methylene bridges
  • Carboxylic acid groups

Correct Answer: Tertiary amine nitrogen atoms linked by methylene bridges

Q8. Hexamine is synthesized industrially by the condensation of:

  • Formaldehyde and ammonia
  • Acetaldehyde and ammonium chloride
  • Formic acid and urea
  • Acetone and hydrazine

Correct Answer: Formaldehyde and ammonia

Q9. The antimicrobial action of methenamine in urine depends mainly on:

  • Urinary alkalinity above pH 8
  • Renal clearance rate only
  • Acidic urine to generate formaldehyde
  • Concurrent administration of diuretics

Correct Answer: Acidic urine to generate formaldehyde

Q10. Hexamine’s molar mass (approximate) is closest to which value?

  • 58 g/mol
  • 140 g/mol
  • 200 g/mol
  • 300 g/mol

Correct Answer: 140 g/mol

Q11. In pharmaceutical formulations, methenamine salts used as urinary antiseptics are combined with:

  • Alkali metal hydroxides to raise urine pH
  • Urinary acidifiers like hippuric or mandelic acid salts
  • Systemic corticosteroids
  • Intravenous amino acids

Correct Answer: Urinary acidifiers like hippuric or mandelic acid salts

Q12. Which of the following statements about hexamine stability is correct?

  • It is highly reactive and unstable at room temperature
  • It decomposes readily in neutral solution
  • It is stable in neutral and alkaline conditions but decomposes in strong acid
  • It sublimes at physiological temperature

Correct Answer: It is stable in neutral and alkaline conditions but decomposes in strong acid

Q13. A major safety concern with methenamine therapy is related to:

  • Production of nitrites in alkaline urine
  • Formaldehyde-related bladder irritation and toxicity
  • Severe hypoglycemia
  • Ototoxicity

Correct Answer: Formaldehyde-related bladder irritation and toxicity

Q14. Hexamine is least likely to be used in which pharmaceutical role?

  • Urinary antiseptic
  • Formaldehyde donor in resin chemistry
  • General systemic antibiotic for bloodstream infections
  • Component of solid fuel tablets

Correct Answer: General systemic antibiotic for bloodstream infections

Q15. The therapeutic efficacy of methenamine depends on which patient factor?

  • Urine pH being acidic
  • Liver enzyme induction
  • High plasma protein binding
  • Concurrent anticoagulant therapy

Correct Answer: Urine pH being acidic

Q16. Which of the following is a contraindication to methenamine use?

  • Renal impairment with reduced urine output
  • Uncomplicated lower urinary tract infection with acidic urine
  • Mild dehydration easily corrected
  • Use in combination with urinary acidifiers under supervision

Correct Answer: Renal impairment with reduced urine output

Q17. Chemical behavior: hexamine reacts with strong mineral acids to yield:

  • Formaldehyde and ammonium salts
  • Hydrazine and water
  • Urea and methane
  • Nitric oxide

Correct Answer: Formaldehyde and ammonium salts

Q18. Which salt form of methenamine is commonly prescribed to maintain urinary antiseptic activity?

  • Methenamine sulfate
  • Methenamine chloride
  • Methenamine hippurate
  • Methenamine phosphate

Correct Answer: Methenamine hippurate

Q19. Hexamine’s cage structure contains how many nitrogen atoms?

  • Two
  • Four
  • Six
  • Eight

Correct Answer: Four

Q20. The mode of bactericidal action of formaldehyde generated from methenamine primarily involves:

  • Disruption of bacterial cell wall synthesis only
  • Protein cross-linking and nucleic acid damage
  • Selective inhibition of folate synthesis
  • Competitive antagonism of bacterial ribosomes

Correct Answer: Protein cross-linking and nucleic acid damage

Q21. In formulation chemistry, hexamine is used as a:

  • Plasticizer for PVC
  • Crosslinking agent and hardener in phenolic resins
  • Primary solvent for lipophilic drugs
  • Nonionic surfactant

Correct Answer: Crosslinking agent and hardener in phenolic resins

Q22. Which statement about methenamine absorption and systemic antimicrobial effect is correct?

  • Methenamine produces strong systemic antimicrobial levels after oral dosing
  • It is not used for systemic infections because its activity is local in the urinary tract after conversion to formaldehyde
  • It accumulates in fatty tissues to provide prolonged systemic action
  • It is only active when administered intravenously

Correct Answer: It is not used for systemic infections because its activity is local in the urinary tract after conversion to formaldehyde

Q23. A common over-the-counter application of hexamine unrelated to pharmaceuticals is:

  • Fuel tablets for camping stoves
  • Topical antiseptic cream
  • Toothpaste whitening agent
  • Inhaler propellant

Correct Answer: Fuel tablets for camping stoves

Q24. Which laboratory test indicates the conversion of hexamine to formaldehyde?

  • Ninhydrin test
  • Schiff’s reagent producing a magenta/pink color
  • Bromothymol blue color change
  • Silver mirror test

Correct Answer: Schiff’s reagent producing a magenta/pink color

Q25. The presence of which co-administered drug could reduce the effectiveness of methenamine by increasing urinary pH?

  • Ascorbic acid
  • Sodium bicarbonate
  • Methenamine hippurate
  • As sulfonamide antibiotic

Correct Answer: Sodium bicarbonate

Q26. Which microbial groups are generally susceptible to formaldehyde produced from methenamine?

  • Most bacteria including common urinary pathogens
  • Only fungal pathogens
  • Only viruses
  • Only anaerobic bacteria

Correct Answer: Most bacteria including common urinary pathogens

Q27. Which adverse effect is commonly reported with oral methenamine therapy?

  • Severe hypokalemia
  • Gastrointestinal irritation and dysuria
  • Hematologic aplasia
  • Acute cholestatic jaundice

Correct Answer: Gastrointestinal irritation and dysuria

Q28. To ensure effective bactericidal activity in the urinary tract, target urinary pH should be approximately:

  • 8.5–9.5
  • Neutral (7.0)
  • Acidic (≤5.5)
  • Extremely alkaline (>10)

Correct Answer: Acidic (≤5.5)

Q29. In industrial chemistry, hexamine is a precursor for which high-energy material?

  • TNT (trinitrotoluene)
  • RDX (cyclonite)
  • Nitroglycerin
  • ANFO (ammonium nitrate/fuel oil)

Correct Answer: RDX (cyclonite)

Q30. Which statement about hexamine solubility is accurate?

  • It is insoluble in water
  • It is soluble in water and polar solvents
  • It only dissolves in nonpolar solvents like hexane
  • It sublimes without dissolving

Correct Answer: It is soluble in water and polar solvents

Q31. Which patient counseling point is important for a patient taking methenamine hippurate?

  • Take with large amounts of alkaline beverages to activate the drug
  • Maintain urine acidity and avoid alkaline agents to ensure activity
  • Stop taking if urine becomes acidic
  • Use as a rapid systemic antibiotic for fever control

Correct Answer: Maintain urine acidity and avoid alkaline agents to ensure activity

Q32. Which laboratory parameter contraindicates the use of methenamine?

  • Normal renal function
  • Elevated serum creatinine indicating renal impairment
  • Low liver transaminases
  • High hemoglobin without symptoms

Correct Answer: Elevated serum creatinine indicating renal impairment

Q33. Which synthetic role can hexamine perform in organic chemistry relevant to drug synthesis?

  • Act as a dehydrating agent to form esters
  • Serve as a convenient formaldehyde source for Mannich-type reactions
  • Function as a reducing agent similar to LiAlH4
  • Directly alkylate aromatic rings without catalysts

Correct Answer: Serve as a convenient formaldehyde source for Mannich-type reactions

Q34. Which statement about methenamine drug interactions is true?

  • Antacids and alkalizing agents can reduce its efficacy by raising urine pH
  • Sulfonamides inactivate methenamine by chemical reaction in vivo
  • ACE inhibitors potentiate methenamine action
  • Warfarin increases methenamine decomposition

Correct Answer: Antacids and alkalizing agents can reduce its efficacy by raising urine pH

Q35. The IUPAC or commonly used synonym for hexamine used in many pharmacopeias is:

  • Methenamine
  • Hexachlorophene
  • Metronidazole
  • Hexylamine

Correct Answer: Methenamine

Q36. Which property of hexamine makes it useful in solid fuel tablets?

  • High volatility at room temperature
  • High energy content and clean combustion
  • Strong acidic nature
  • Ability to polymerize on heating

Correct Answer: High energy content and clean combustion

Q37. Methenamine is inactive against urinary pathogens when urine pH is raised above:

  • 9.0
  • 7.0
  • 6.0
  • 5.5

Correct Answer: 6.0

Q38. Which formulation consideration is important when preparing methenamine tablets for stability?

  • Incorporation of strong acids in tablet core to prematurely release formaldehyde
  • Avoiding moisture and acidic excipients that could cause decomposition during storage
  • Ensuring tablets contain enzymatic activators to metabolize methenamine
  • Coating with basic salts to maintain high pH

Correct Answer: Avoiding moisture and acidic excipients that could cause decomposition during storage

Q39. In pediatric use, methenamine dosing must be cautious because of:

  • High risk of hemolytic anemia in G6PD deficiency
  • Tendency to cause hyperactivity in children
  • Enhanced formaldehyde formation with low urine volumes
  • Direct hepatotoxicity even at low doses

Correct Answer: Enhanced formaldehyde formation with low urine volumes

Q40. Which analytical method is commonly used to identify hexamine in bulk drug analysis?

  • UV-visible spectrophotometry at 260 nm
  • Infrared (IR) spectroscopy showing characteristic C–N stretches
  • Atomic absorption spectroscopy for metals
  • Polarimetry for optical rotation

Correct Answer: Infrared (IR) spectroscopy showing characteristic C–N stretches

Q41. Which clinical scenario would favor using methenamine for prophylaxis?

  • Acute pyelonephritis requiring IV antibiotics
  • Recurrent lower urinary tract infections where urine can be acidified
  • Sepsis of unknown origin
  • Viral cystitis

Correct Answer: Recurrent lower urinary tract infections where urine can be acidified

Q42. Which enzymatic pathway is directly responsible for converting methenamine to formaldehyde in vivo?

  • Liver cytochrome P450 oxidation
  • No enzymatic pathway; acid-catalyzed hydrolysis in urine
  • Renal dehydrogenase-mediated conversion
  • Mitochondrial oxidative decarboxylation

Correct Answer: No enzymatic pathway; acid-catalyzed hydrolysis in urine

Q43. Which of the following is a structural descriptor of hexamine?

  • Conjugated aromatic heterocycle
  • Tetramethylene bridged tertiary amine cage
  • Linear polypeptide
  • Saturated polyol

Correct Answer: Tetramethylene bridged tertiary amine cage

Q44. Incompatibility issues: hexamine should not be stored with:

  • Strong acids that can cause decomposition
  • Neutral glass containers
  • Dry desiccants
  • Hermetic metal containers

Correct Answer: Strong acids that can cause decomposition

Q45. Which pharmacokinetic property explains why methenamine is effective only in the urine?

  • Extensive hepatic metabolism to active systemic antibiotics
  • It is excreted unchanged into urine where it is converted to formaldehyde
  • High plasma protein binding delivers it to tissues systemically
  • Long half-life provides sustained plasma levels

Correct Answer: It is excreted unchanged into urine where it is converted to formaldehyde

Q46. Which regulatory or safety issue is relevant to hexamine-containing products?

  • Risk of explosive derivatives in industrial processing (e.g., RDX synthesis)
  • Guaranteed safe storage with strong oxidizers
  • No restrictions due to complete lack of toxicity
  • Requirement to be refrigerated at all times

Correct Answer: Risk of explosive derivatives in industrial processing (e.g., RDX synthesis)

Q47. Methenamine is least effective against urinary pathogens when used with which dietary habit?

  • Eating acidic foods that lower urine pH
  • Drinking large amounts of alkaline mineral water
  • Consuming vitamin C to acidify urine
  • Maintaining normal hydration with neutral fluids

Correct Answer: Drinking large amounts of alkaline mineral water

Q48. Which clinical monitoring is important during long-term methenamine prophylaxis?

  • Regular urine pH checks and renal function tests
  • Daily liver biopsy
  • Continuous ECG monitoring
  • Monthly pulmonary function tests

Correct Answer: Regular urine pH checks and renal function tests

Q49. Which of the following best describes methenamine’s classification in antimicrobial therapy?

  • Broad-spectrum systemic antibiotic
  • Urinary antiseptic that acts via chemical release of a disinfectant
  • Topical steroidal anti-inflammatory
  • Antifungal prodrug activated by hepatic enzymes

Correct Answer: Urinary antiseptic that acts via chemical release of a disinfectant

Q50. For exam-level structural recognition: hexamine can be considered a polymeric assembly of how many methylene-linked nitrogen units?

  • Two nitrogen units linked by three methylene groups
  • Four tertiary nitrogen atoms linked through six methylene bridges forming a cage
  • One central nitrogen atom with six alkyl substituents
  • Eight nitrogen atoms in a linear chain

Correct Answer: Four tertiary nitrogen atoms linked through six methylene bridges forming a cage

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