Tablet coating is a critical pharmaceutical process that enhances tablet stability, aesthetics, and patient acceptability while enabling functional objectives such as taste masking, enteric protection and modified drug release. Key concepts include types of coating—film coating, sugar coating and enteric coating—along with coating materials like HPMC, cellulose derivatives, Eudragit, plasticizers (triethyl citrate, PEG), pigments, and solvents (aqueous vs organic). Process parameters such as spray rate, atomization, inlet air temperature and coating weight gain influence coat uniformity, defects and dissolution performance. Coating equipment ranges from conventional coating pans to fluidized bed and Wurster systems. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of film coating on immediate-release tablets?
- To convert tablets into sustained-release forms
- To provide enteric protection at low pH
- To improve appearance, swallowability and protect from moisture
- To increase active drug potency
Correct Answer: To improve appearance, swallowability and protect from moisture
Q2. Which polymer is commonly used as an aqueous film-former in tablet coating?
- Cellulose acetate phthalate (CAP)
- Hydroxypropyl methylcellulose (HPMC)
- Dibutyl phthalate (DBP)
- Sodium lauryl sulfate (SLS)
Correct Answer: Hydroxypropyl methylcellulose (HPMC)
Q3. Enteric coating polymers are designed to resist dissolution at which condition?
- High ionic strength
- Low shear
- Low pH of the stomach
- Elevated temperatures
Correct Answer: Low pH of the stomach
Q4. Which plasticizer is commonly added to increase flexibility of a polymer film?
- Triethyl citrate
- Titanium dioxide
- Hydroxypropyl methylcellulose
- Magnesium stearate
Correct Answer: Triethyl citrate
Q5. What defect is characterized by small craters or dimples on the coated surface due to solvent entrapment?
- Peeling
- Mottling
- Pitting
- Bridging
Correct Answer: Pitting
Q6. Which coating technique is most suitable for taste masking of pellets or small particles?
- Traditional sugar coating in a large pan
- Wurster fluidized bed coating
- Compression coating
- Dip coating with molten wax
Correct Answer: Wurster fluidized bed coating
Q7. Coating weight gain is usually expressed as:
- Absolute coat thickness in micrometers
- Percentage increase in tablet weight
- Amount of polymer per batch in grams
- Coating spray rate in mL/min
Correct Answer: Percentage increase in tablet weight
Q8. Which of the following solvents is preferred for environmentally friendly aqueous coating?
- Acetone
- Ethanol
- Water
- Methylene chloride
Correct Answer: Water
Q9. Mottling in coated tablets is often caused by:
- Inadequate film-former molecular weight
- Uneven distribution of pigment or solubility differences
- Excessive coating weight gain only
- High compression force during tablet manufacture
Correct Answer: Uneven distribution of pigment or solubility differences
Q10. Which polymer is commonly used for enteric coatings with dissolution above pH 5.5–6.8?
- Hypromellose acetate succinate (HPMCAS)
- Hydroxypropyl methylcellulose (HPMC)
- Polyethylene glycol 4000
- Triethyl citrate
Correct Answer: Hypromellose acetate succinate (HPMCAS)
Q11. During spray coating, increasing atomization pressure primarily affects:
- The polymer molecular weight
- Droplet size and spray pattern
- Tablet core porosity
- Color of the final film
Correct Answer: Droplet size and spray pattern
Q12. Which excipient serves as an opacifier and pigment in coating formulations?
- Talc
- Titanium dioxide
- Magnesium stearate
- Polysorbate 80
Correct Answer: Titanium dioxide
Q13. A common analytical method to assess coating uniformity and thickness is:
- UV‑Vis spectrophotometry of core API
- Scanning electron microscopy (SEM)
- Disintegration testing in water
- Loss on drying
Correct Answer: Scanning electron microscopy (SEM)
Q14. Which coating defect results in film separation from the tablet edges after storage?
- Picking
- Peeling
- Bridging
- Mottling
Correct Answer: Peeling
Q15. The term “Wurster process” refers to which coating principle?
- Pan coating with sugar syrup
- Top spray fluidized bed for particle layering
- Electrostatic deposition of pigments
- Compression coating of a core
Correct Answer: Top spray fluidized bed for particle layering
Q16. Which parameter must be controlled to avoid overwetting and sticking during coating?
- Coating pan rotation only
- Tablet hardness only
- Spray rate and inlet air temperature
- Packaging humidity after coating
Correct Answer: Spray rate and inlet air temperature
Q17. Plasticizers reduce water uptake and also:
- Increase polymer glass transition temperature (Tg)
- Lower polymer glass transition temperature (Tg)
- Increase tablet disintegration time directly
- Eliminate the need for pigments
Correct Answer: Lower polymer glass transition temperature (Tg)
Q18. Which polymer is classically used for enteric coating in older formulations?
- Ethyl cellulose
- Cellulose acetate phthalate (CAP)
- Polyvinylpyrrolidone (PVP)
- Hydroxypropyl cellulose (HPC)
Correct Answer: Cellulose acetate phthalate (CAP)
Q19. What is the main advantage of aqueous coating over organic solvent-based coating?
- Faster drying times always
- Lower risk of flammability and toxicity
- Higher coating-gloss performance exclusively
- It eliminates need for plasticizers
Correct Answer: Lower risk of flammability and toxicity
Q20. Which test directly evaluates whether an enteric coat is functioning correctly?
- Friability test
- Disintegration and sequential dissolution in pH 1.2 then pH 6.8
- Hardness test at room pH
- Moisture sorption isotherm
Correct Answer: Disintegration and sequential dissolution in pH 1.2 then pH 6.8
Q21. In coating, “spray drying” refers to:
- Applying molten wax to tablet surface
- Atomizing coating solution into heated air to form dry droplets on tablets
- Removing tablets from pan and oven-drying only
- Using ethanol-only systems for faster curing
Correct Answer: Atomizing coating solution into heated air to form dry droplets on tablets
Q22. Which coating defect is characterized by film rupture in deep concave areas of a tablet?
- Picking
- Chipping
- Bridging
- Peeling
Correct Answer: Bridging
Q23. Kollicoat and Opadry are examples of:
- Plasticizers
- Commercial ready-to-use coating systems
- Pore-formers for osmotic tablets
- Solvents used in organic coatings
Correct Answer: Commercial ready-to-use coating systems
Q24. A higher coating weight gain generally leads to:
- Thinner film thickness
- No change in dissolution profile
- Increased film thickness and possible modification of drug release
- Instant disintegration improvement
Correct Answer: Increased film thickness and possible modification of drug release
Q25. Which of the following is NOT typically a role of a coating plasticizer?
- Improve film flexibility
- Reduce film brittleness
- Increase polymer Tg
- Enhance elongation of the film
Correct Answer: Increase polymer Tg
Q26. During scale-up from lab to production, a critical challenge for coating is:
- Changing the chemical identity of the polymer
- Maintaining equivalent spray droplet size and drying conditions
- Eliminating the need for pigments
- Switching from aqueous to organic systems without testing
Correct Answer: Maintaining equivalent spray droplet size and drying conditions
Q27. Which coating material is often used to impart sustained-release properties by forming a semi-permeable membrane?
- Ethyl cellulose
- Titanium dioxide
- Hydroxypropyl methylcellulose (HPMC)
- Polyethylene glycol 400
Correct Answer: Ethyl cellulose
Q28. What is a common remedial action to reduce mottling caused by pigment solubility differences?
- Increase tablet compression force
- Adjust pigment selection, improve mixing and control spray solution pH
- Lower inlet air temperature drastically
- Remove plasticizer from the formula
Correct Answer: Adjust pigment selection, improve mixing and control spray solution pH
Q29. Which parameter is least likely to influence gloss and color uniformity of a coated tablet?
- Drying temperature and humidity
- Airflow pattern in the coater
- Tablet core active ingredient potency
- Pigment dispersion quality
Correct Answer: Tablet core active ingredient potency
Q30. For a pH‑dependent enteric coat that dissolves at pH > 5.5, which in-vitro test result indicates failure?
- No drug release in pH 1.2 for 2 hours, followed by release in pH 6.8
- Immediate drug release in pH 1.2 within 30 minutes
- Complete release only after mechanical abrasion
- Consistent lag-time followed by rapid release at pH 6.8
Correct Answer: Immediate drug release in pH 1.2 within 30 minutes
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