Introduction: Excipients in parenteral formulations are inactive ingredients added to injectable products to ensure stability, sterility, safety and effective delivery. B. Pharm students must understand common excipient classes—tonicity agents, buffers, preservatives, solubilizers, antioxidants, stabilizers, chelators, bulking agents and cryoprotectants—and their roles in IV, IM and SC preparations. Key considerations include compatibility, pH control, osmolarity/tonicity, pyrogen control, container-closure interactions and regulatory requirements (USP, pharmacopeial tests). Knowledge of excipient selection, incompatibilities, and effects of sterilization or lyophilization is essential for designing safe parenteral medicines. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of excipients in parenteral formulations?
- To provide color and flavor to injections
- To improve stability, solubility, sterility and administration of the drug
- To increase the drug’s pharmacological activity
- To lengthen the label storage time only
Correct Answer: To improve stability, solubility, sterility and administration of the drug
Q2. Which excipient class is commonly used to adjust tonicity in intravenous solutions?
- Buffers (e.g., phosphate)
- Surfactants (e.g., polysorbate)
- Tonicity agents (e.g., sodium chloride, dextrose)
- Preservatives (e.g., benzyl alcohol)
Correct Answer: Tonicity agents (e.g., sodium chloride, dextrose)
Q3. Which buffer system is frequently used in parenteral formulations for physiological pH control?
- Citrate and phosphate buffers
- Acetic acid–acetate only
- Tris buffer exclusively
- Hydrochloric acid as a buffer
Correct Answer: Citrate and phosphate buffers
Q4. Which preservative is contraindicated or used with caution in neonates due to “gasping syndrome”?
- Chlorobutanol
- Benzyl alcohol
- Phenol
- Methylparaben
Correct Answer: Benzyl alcohol
Q5. Which excipient class prevents oxidative degradation of susceptible drugs?
- Antioxidants (e.g., sodium metabisulfite, ascorbic acid)
- Buffers (e.g., phosphate)
- Bulking agents (e.g., mannitol)
- Preservatives (e.g., phenol)
Correct Answer: Antioxidants (e.g., sodium metabisulfite, ascorbic acid)
Q6. Which chelating agent is commonly used to complex trace metal ions and reduce metal-catalyzed oxidation?
- Polysorbate 80
- EDTA (ethylenediaminetetraacetic acid)
- Sorbitol
- MCT oil
Correct Answer: EDTA (ethylenediaminetetraacetic acid)
Q7. Which excipient is used as a bulking agent and cryoprotectant in lyophilized parenteral products?
- Mannitol as bulking agent and sucrose/trehalose as cryoprotectants
- Benzalkonium chloride
- Poloxamer 188 only
- Glycerin for coloring
Correct Answer: Mannitol as bulking agent and sucrose/trehalose as cryoprotectants
Q8. Which surfactant is commonly used to prevent adsorption of proteins to container surfaces in parenterals?
- Sodium chloride
- Polysorbate 80 (Tween 80)
- Phenol
- Propylene glycol
Correct Answer: Polysorbate 80 (Tween 80)
Q9. Which preservative is often used in multidose parenteral formulations for antimicrobial activity?
- Sodium chloride
- Phenol or parabens (methyl/propylparaben)
- Trehalose
- EDTA as sole preservative
Correct Answer: Phenol or parabens (methyl/propylparaben)
Q10. Why must parenteral formulations be isotonic or near-isotonic?
- To enhance the smell of the solution
- To prevent tissue irritation, hemolysis and pain on injection
- To increase preservative potency
- To make sterilization unnecessary
Correct Answer: To prevent tissue irritation, hemolysis and pain on injection
Q11. Which excipient can act as both solvent and tonicity agent in parenterals?
- Polysorbate 80
- Water for injection (WFI) only
- Dextrose solution
- EDTA
Correct Answer: Dextrose solution
Q12. Which of the following is a risk associated with using surfactants (e.g., polysorbates) in protein parenterals?
- Enhancement of protein aggregation due to polysorbate degradation products
- Complete sterilization of the product
- Increased tonicity only
- Elimination of need for buffers
Correct Answer: Enhancement of protein aggregation due to polysorbate degradation products
Q13. Which excipient is most appropriate to control pH to match the pKa of an injectable weak acid drug?
- Buffer system (e.g., phosphate buffer)
- Antioxidant
- Preservative
- Bulking agent like mannitol
Correct Answer: Buffer system (e.g., phosphate buffer)
Q14. For parenteral emulsions, which excipient class stabilizes oil droplets?
- Chelating agents
- Emulsifiers/surfactants (e.g., lecithin, polysorbates)
- Antioxidants only
- Bulking agents
Correct Answer: Emulsifiers/surfactants (e.g., lecithin, polysorbates)
Q15. What is the main role of bulking agents in lyophilized parenteral products?
- To provide antimicrobial activity
- To give cake structure and improve reconstitution properties
- To act as primary preservative
- To cause rapid oxidation
Correct Answer: To give cake structure and improve reconstitution properties
Q16. Which test is essential to detect pyrogenic contaminants in parenteral products?
- Antimicrobial effectiveness test (AET)
- USP bacterial endotoxins test (BET) / LAL test
- Assay of active ingredient only
- pH measurement alone
Correct Answer: USP bacterial endotoxins test (BET) / LAL test
Q17. Which cosolvent is commonly used to increase solubility of poorly soluble drugs for parenteral use?
- Polyethylene glycol (PEG) and propylene glycol as cosolvents
- EDTA
- Sodium chloride as cosolvent
- Polysorbate 80 as primary cosolvent
Correct Answer: Polyethylene glycol (PEG) and propylene glycol as cosolvents
Q18. Which excipient can help prevent metal-catalyzed oxidation of parenteral products?
- EDTA (chelating agent)
- Poloxamer alone
- Mannitol as antioxidant
- Phenol as chelator
Correct Answer: EDTA (chelating agent)
Q19. Which container-closure interaction concern is specifically related to plastic containers for parenterals?
- Leaching of plasticizers and adsorption of drug to polymer surfaces
- Spontaneous sterilization by plastics
- Immediate pH neutralization
- Complete prevention of oxidation
Correct Answer: Leaching of plasticizers and adsorption of drug to polymer surfaces
Q20. What is the effect of autoclave sterilization on certain excipients?
- No effect on any excipient
- Thermal degradation or hydrolysis of heat-sensitive excipients
- Always improves antimicrobial effectiveness without changes
- Converts preservatives into buffers
Correct Answer: Thermal degradation or hydrolysis of heat-sensitive excipients
Q21. Why are preservatives generally not used in single-dose parenteral vials?
- They are too costly for single-dose vials
- Single-dose vials are used once and sterility is maintained without preservatives
- Preservatives enhance drug potency in single-dose only
- Regulatory guidelines forbid any excipient in single-dose vials
Correct Answer: Single-dose vials are used once and sterility is maintained without preservatives
Q22. Which excipient is often added to parenteral protein formulations to stabilize proteins during freeze-drying and reconstitution?
- Perchlorate
- Sugars such as sucrose or trehalose
- Sodium chloride only
- Phenol as stabilizer
Correct Answer: Sugars such as sucrose or trehalose
Q23. What is the role of propylene glycol in some parenteral formulations?
- Primary preservative
- Cosolvent to enhance solubility of lipophilic drugs
- Bulking agent for lyophilization
- Chelating agent for metals
Correct Answer: Cosolvent to enhance solubility of lipophilic drugs
Q24. Which parameter must be considered when selecting a buffer for an injectable protein formulation?
- Buffer capacity at pH far from protein’s stability range only
- Buffer’s interaction with protein, ionic strength and pH stability
- Color imparted by the buffer
- Buffer should always be highly concentrated regardless of effect
Correct Answer: Buffer’s interaction with protein, ionic strength and pH stability
Q25. Which excipient is commonly used to reduce aggregation and shear-induced damage during parenteral administration of biologics?
- Surfactants like polysorbates or poloxamers
- EDTA as surfactant
- Sodium chloride to denature proteins
- Mannitol to cause aggregation
Correct Answer: Surfactants like polysorbates or poloxamers
Q26. What is the main regulatory requirement regarding excipients used in parenteral products?
- Excipients must be listed but not evaluated for safety
- Excipients must meet pharmacopeial quality standards and demonstrated compatibility and safety
- No documentation is required for parenteral excipients
- Only flavoring excipients are regulated
Correct Answer: Excipients must meet pharmacopeial quality standards and demonstrated compatibility and safety
Q27. Which excipient can act as both a stabilizer and a tonicity modifier in parenteral solutions?
- Sucrose or sorbitol as stabilizers and tonicity modifiers
- Phenol only
- EDTA as tonicity modifier
- Polysorbate 80 as sole tonicity agent
Correct Answer: Sucrose or sorbitol as stabilizers and tonicity modifiers
Q28. What is the concern when combining certain preservatives with aluminum-containing adjuvants or ions in parenterals?
- Preservatives will never interact with ions
- Adsorption or inactivation of preservative, reducing antimicrobial efficacy
- Complete neutralization of pH beneficially
- Enhanced solubility of drug only
Correct Answer: Adsorption or inactivation of preservative, reducing antimicrobial efficacy
Q29. Which excipient is often avoided in large-volume parenterals for neonates because of toxicity risk?
- Trehalose
- Benzyl alcohol
- Sucrose
- Mannitol
Correct Answer: Benzyl alcohol
Q30. Which assessment is important to ensure particulate matter control related to excipients in parenterals?
- Visual inspection, subvisible particle testing (light obscuration) and compatibility studies
- Only pH testing is necessary
- Only sterility test covers particulate matter
- No testing required for excipient-related particles
Correct Answer: Visual inspection, subvisible particle testing (light obscuration) and compatibility studies
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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