Monophasic liquids – Enemas MCQs With Answer

Introduction

Monophasic liquids – enemas are single-phase liquid dosage forms designed for rectal administration to achieve local cleansing, local therapy, or systemic effects. For B. Pharm students, key formulation concepts include vehicle selection (aqueous vs oily), isotonicity, pH near neutrality, viscosity modulation for retention, appropriate volume (micro, retention, and evacuation enemas), and excipient choices such as preservatives and surfactants. Clinical considerations span indications (constipation, ulcerative colitis), administration technique (Sims’ position, nozzle depth, temperature), packaging, labeling (“For rectal use only”), microbial quality, and safety issues like electrolyte disturbances with hypertonic phosphate enemas. Understanding pharmacokinetics (partial first-pass avoidance) and quality control helps ensure safe, effective products. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. In pharmaceutics, what best describes an enema under monophasic liquids?

• A suspension intended for intramuscular injection
• Solutions intended for administration into the rectum
• A semisolid applied to mucosa for local action
• An emulsion for intravenous infusion

Correct Answer: Solutions intended for administration into the rectum

Q2. What are the primary clinical categories of enemas?

• Oral and parenteral
• Evacuation and retention
• Topical and transdermal
• Immediate-release and sustained-release

Correct Answer: Evacuation and retention

Q3. Typical adult volume range for an evacuation (cleansing) enema is:

• 5–10 mL
• 25–100 mL
• 500–1000 mL
• 1500–2000 mL

Correct Answer: 500–1000 mL

Q4. Typical adult volume range for a retention enema is:

• 5–10 mL
• 25–100 mL
• 250–500 mL
• 500–1000 mL

Correct Answer: 25–100 mL

Q5. A “micro-enema” most commonly contains approximately:

• 5–10 mL
• 25–50 mL
• 250–500 mL
• 1000–1500 mL

Correct Answer: 5–10 mL

Q6. For stool-softening retention enemas, the preferred vehicle is often:

• Oily vehicles such as mineral/vegetable oil
• Hypertonic dextrose solution
• Strong acidic aqueous solution (pH 2–3)
• Alcoholic solution (ethanol >40%)

Correct Answer: Oily vehicles such as mineral/vegetable oil

Q7. To minimize fluid and electrolyte shifts, a large-volume evacuation enema should be:

• Hypertonic relative to plasma
• Hypotonic relative to plasma
• Isotonic with plasma
• Azeotropic with ethanol

Correct Answer: Isotonic with plasma

Q8. Hypertonic phosphate enemas promote defecation primarily by:

• Blocking cholinergic receptors in the colon
• Drawing water into the lumen by osmotic action
• Inhibiting intestinal Na+/K+ ATPase
• Neutralizing gastric acid

Correct Answer: Drawing water into the lumen by osmotic action

Q9. The recommended administration temperature for most enemas to reduce cramping is:

• Cold (4–10°C)
• Below room temperature (10–20°C)
• Near body temperature (about 37°C)
• Hot (45–50°C)

Correct Answer: Near body temperature (about 37°C)

Q10. The preferred position for administering an enema is:

• Supine with legs extended
• Prone with head low
• Left lateral (Sims’) position
• Upright sitting

Correct Answer: Left lateral (Sims’) position

Q11. Typical adult nozzle insertion depth for an enema is approximately:

• 1–2 cm
• 5–7 cm
• 10–12 cm
• 15–20 cm

Correct Answer: 5–7 cm

Q12. A pharmacokinetic advantage of rectal enemas is:

• Complete avoidance of first-pass metabolism
• Partial bypass of hepatic first-pass metabolism
• Unlimited absorption regardless of rectal contents
• Faster than intravenous administration

Correct Answer: Partial bypass of hepatic first-pass metabolism

Q13. The rectal environment is best characterized as:

• Highly acidic with strong buffering capacity
• Highly alkaline with strong buffering capacity
• Near-neutral pH with low buffering capacity
• Neutral pH with high buffering capacity

Correct Answer: Near-neutral pH with low buffering capacity

Q14. A commonly used preservative system for aqueous enema solutions is:

• Parabens (methyl/propyl paraben)
• Formaldehyde solution
• Strong iodine tincture
• Chlorinated hydrocarbons

Correct Answer: Parabens (methyl/propyl paraben)

Q15. Which statement about microbiological quality of enemas is most accurate?

• All enemas must be sterile by regulation
• Enemas need only be pyrogen-free
• Enemas should meet microbial limit tests even if not sterile
• Microbial quality is irrelevant for rectal products

Correct Answer: Enemas should meet microbial limit tests even if not sterile

Q16. An essential labeling requirement for enemas is:

• “For oral use only”
• “Shake well before use” for all enemas
• “For rectal use only”
• “For intrathecal use only”

Correct Answer: “For rectal use only”

Q17. To enhance retention time of a medicated enema, formulators often:

• Decrease viscosity using alcohol
• Increase viscosity using hydrophilic polymers
• Make the solution highly acidic (pH 2)
• Add high levels of sodium chloride

Correct Answer: Increase viscosity using hydrophilic polymers

Q18. A drug commonly delivered via enema for local therapy in ulcerative colitis is:

• Mesalazine (5-ASA)
• Insulin
• Amoxicillin
• Furosemide

Correct Answer: Mesalazine (5-ASA)

Q19. Hypertonic phosphate enemas are relatively contraindicated in patients with:

• Mild seasonal allergies
• Renal impairment
• Acne vulgaris
• Hypothyroidism

Correct Answer: Renal impairment

Q20. A potential risk of frequent hypertonic enema use is:

• Severe hypoglycemia
• Electrolyte imbalance
• Permanent liver failure
• Irreversible blindness

Correct Answer: Electrolyte imbalance

Q21. Compared with suppositories, enemas can:

• Deliver larger liquid volumes rectally
• Never cause irritation
• Always achieve higher bioavailability
• Be stored without any microbial controls

Correct Answer: Deliver larger liquid volumes rectally

Q22. Which factor most likely reduces systemic drug absorption from enemas?

• Empty rectum
• Presence of fecal matter
• Near-neutral pH
• Body temperature administration

Correct Answer: Presence of fecal matter

Q23. The most common primary packaging for OTC enemas is:

• Glass ampoules with rubber stoppers
• Prefilled plastic squeeze bottles with applicator nozzles
• Metal aerosol canisters
• Multi-dose vials for injection

Correct Answer: Prefilled plastic squeeze bottles with applicator nozzles

Q24. When adjusting isotonicity of an aqueous enema, pharmacists often use:

• Henderson–Hasselbalch equation
• Blender’s solubility rule
• Sodium chloride equivalent (E-value) method
• Arrhenius equation

Correct Answer: Sodium chloride equivalent (E-value) method

Q25. A suitable nonionic surfactant/wetting agent for enemas (minimizing irritation) is:

• Polysorbate 80
• Sodium lauryl sulfate
• Cetrimide
• Chlorhexidine

Correct Answer: Polysorbate 80

Q26. Regarding drug release from enemas, which is generally true?

• Oily vehicles release hydrophilic drugs faster than aqueous vehicles
• Aqueous vehicles typically allow faster drug availability than oily vehicles
• Vehicle choice does not affect release
• Only emulsions control release rate

Correct Answer: Aqueous vehicles typically allow faster drug availability than oily vehicles

Q27. Rectal diazepam solution is used primarily for:

• Acute seizure management
• Hypertension
• Diabetic ketoacidosis
• Hyperlipidemia

Correct Answer: Acute seizure management

Q28. An appropriate evacuation enema volume for a school-age child is approximately:

• 25–50 mL
• 100–150 mL
• 250–500 mL
• 1000–1500 mL

Correct Answer: 250–500 mL

Q29. To protect an oxidation-prone drug in an aqueous enema, a suitable antioxidant is:

• Sodium metabisulfite
• Butylated hydroxytoluene (BHT) only
• Peroxide
• Nitric acid

Correct Answer: Sodium metabisulfite

Q30. A common instrument to measure viscosity of Newtonian enema solutions is the:

• Polarimeter
• Ostwald (capillary) viscometer
• pH meter
• Flame photometer

Correct Answer: Ostwald (capillary) viscometer

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