Chemical incompatibilities with examples MCQs With Answer

Chemical incompatibilities with examples MCQs With Answer help B. Pharm students master real-world pharmaceutical science. Chemical incompatibility occurs when active ingredients or excipients react to form new products or lose potency (via oxidation, hydrolysis, precipitation, complexation, photolysis, acid–base reactions), unlike physical incompatibility (e.g., sorption, phase separation) or therapeutic incompatibility (pharmacodynamic). Key concepts include pH control, buffers, solubility product (Ksp), ionic strength, temperature, light sensitivity, redox, ion-exchange, and container–closure interactions (e.g., PVC adsorption). Common examples: calcium–phosphate precipitation in TPN, epinephrine oxidation, tetracycline–calcium chelation, thiopentone precipitation in acidic media, benzalkonium chloride with anionic surfactants, and Maillard reaction with lactose. Prevention uses antioxidants, chelators, order-of-addition, protective packaging, and reliable compatibility data. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which statement best defines chemical incompatibility in pharmaceutics?

• A visible change in dosage form without any chemical reaction
• An interaction causing a chemical reaction that alters identity or potency of components
• An adverse pharmacodynamic interaction at receptor level
• A mere change in taste or color without any potency loss

Correct Answer: An interaction causing a chemical reaction that alters identity or potency of components

Q2. Epinephrine solution turning pink to brown on storage indicates which primary process?

• Hydrolysis
• Adsorption
• Oxidation
• Complexation

Correct Answer: Oxidation

Q3. Which strategy best minimizes epinephrine oxidation in solution?

• Maintain alkaline pH and use borate buffer
• Maintain acidic pH with antioxidant (e.g., sodium metabisulfite) and protect from light/oxygen
• Use nonaqueous vehicle and expose to air
• Add anionic surfactants for stabilization

Correct Answer: Maintain acidic pH with antioxidant (e.g., sodium metabisulfite) and protect from light/oxygen

Q4. Aspirin shows accelerated degradation when mixed with which excipient due to base-catalyzed hydrolysis?

• Magnesium oxide
• Sucrose
• Talc
• Sodium chloride

Correct Answer: Magnesium oxide

Q5. Which combination leads to complexation and reduced absorption upon oral administration?

• Tetracycline with calcium carbonate
• Paracetamol with sucrose
• Metformin with lactose
• Amlodipine with starch

Correct Answer: Tetracycline with calcium carbonate

Q6. Risk of calcium–phosphate precipitation in TPN admixtures increases primarily with:

• Lower pH and low temperature
• Higher pH and higher temperature
• Use of calcium gluconate instead of calcium chloride
• Use of lower amino acid concentration

Correct Answer: Higher pH and higher temperature

Q7. To reduce Ca–Phos precipitation risk in TPN, the preferred calcium salt is:

• Calcium chloride
• Calcium gluconate
• Calcium carbonate
• Calcium lactate

Correct Answer: Calcium gluconate

Q8. What is the recommended order of addition for calcium and phosphate in TPN to minimize precipitation?

• Add calcium first, then phosphate last
• Add phosphate first, thoroughly mix, then add calcium last
• Add both simultaneously under stirring
• Order does not matter

Correct Answer: Add phosphate first, thoroughly mix, then add calcium last

Q9. Which drug should be diluted only in normal saline because it precipitates in dextrose solutions?

• Phenytoin injection
• Vancomycin injection
• Metronidazole injection
• Cefazolin injection

Correct Answer: Phenytoin injection

Q10. Conventional amphotericin B for infusion should be prepared in:

• Normal saline only (NS)
• 5% dextrose only (D5W)
• Lactated Ringer’s only
• Any solution; it is universally compatible

Correct Answer: 5% dextrose only (D5W)

Q11. Mixing silver nitrate with sodium chloride solution results in:

• Formation of soluble silver complexes
• Precipitation of silver chloride
• No reaction; both remain in solution
• Gas evolution

Correct Answer: Precipitation of silver chloride

Q12. Co-infusing sodium bicarbonate with calcium gluconate may cause:

• Increased calcium ionization and solubility
• Precipitation of calcium carbonate
• No effect; they are fully compatible
• Chelation of calcium by bicarbonate

Correct Answer: Precipitation of calcium carbonate

Q13. Which pair shows classic cationic–anionic surfactant incompatibility?

• Polysorbate 80 with cetylpyridinium chloride
• Benzalkonium chloride with sodium lauryl sulfate
• Span 60 with Tween 80
• Poloxamer 188 with sorbitan trioleate

Correct Answer: Benzalkonium chloride with sodium lauryl sulfate

Q14. Which pair forms a eutectic mixture that may liquefy on trituration?

• Menthol and camphor
• Lactose and starch
• Talc and magnesium stearate
• Cellulose and sucrose

Correct Answer: Menthol and camphor

Q15. Co-administration of ciprofloxacin with aluminum–magnesium antacids leads to:

• Enhanced absorption
• Chelation and reduced bioavailability
• Hydrolysis
• Oxidation

Correct Answer: Chelation and reduced bioavailability

Q16. Which drug is highly photosensitive and must be protected from light during infusion?

• Furosemide
• Sodium nitroprusside
• Metoprolol
• Amoxicillin

Correct Answer: Sodium nitroprusside

Q17. Which excipient best limits metal-catalyzed oxidation in solutions?

• Citric acid
• Propylene glycol
• Disodium edetate (EDTA)
• Sorbitol

Correct Answer: Disodium edetate (EDTA)

Q18. Which buffer system should be avoided with catecholamines due to potential complexation and instability?

• Acetate buffer
• Citrate buffer
• Phosphate buffer
• Borate buffer

Correct Answer: Borate buffer

Q19. Cholestyramine reduces the absorption of which drug via ion-exchange binding in the gut?

• Digoxin
• Paracetamol
• Atenolol
• Omeprazole

Correct Answer: Digoxin

Q20. Mixing beta-lactam antibiotics with aminoglycosides in the same IV solution leads to:

• Synergistic bactericidal activity in the bag
• Mutual inactivation due to chemical reaction
• No interaction; stable combination
• Photolysis

Correct Answer: Mutual inactivation due to chemical reaction

Q21. Why is ceftriaxone contraindicated with calcium-containing solutions in neonates?

• Causes oxidation of ceftriaxone
• Forms insoluble precipitates with calcium leading to emboli
• Inhibits calcium absorption
• No clinically relevant interaction

Correct Answer: Forms insoluble precipitates with calcium leading to emboli

Q22. To minimize adsorption loss of nitroglycerin during infusion, the preferred set-up is:

• PVC bag and PVC tubing
• Glass bottle with non-PVC (polyolefin) tubing
• Polycarbonate bottle with PVC tubing
• Any plastic container; adsorption is negligible

Correct Answer: Glass bottle with non-PVC (polyolefin) tubing

Q23. The Maillard reaction, causing browning and potency loss, most likely occurs between:

• Primary amines and lactose
• Carboxylic acids and sucrose
• Quaternary ammonium compounds and mannitol
• Ethers and cellulose

Correct Answer: Primary amines and lactose

Q24. Adding sodium chloride to a saturated silver chloride suspension will:

• Increase solubility via salting-in
• Decrease solubility due to common-ion effect, causing more precipitation
• Have no effect on solubility
• Oxidize chloride ions

Correct Answer: Decrease solubility due to common-ion effect, causing more precipitation

Q25. Raising the pH of a codeine phosphate solution is most likely to cause:

• Improved solubility of the salt
• Precipitation of free base codeine
• No change; codeine is non-ionizable
• Photodegradation

Correct Answer: Precipitation of free base codeine

Q26. Which practice best minimizes photodegradation in light-sensitive parenterals?

• Use of clear containers under bright light
• Use amber containers, cover lines with light-protective tubing, minimize light exposure
• Increase temperature to accelerate dissolution
• Add sodium chloride to increase ionic strength

Correct Answer: Use amber containers, cover lines with light-protective tubing, minimize light exposure

Q27. Which combination can form insoluble precipitates of tannates?

• Alkaloid salts with tannic acid
• Carboxylic acids with sodium bicarbonate
• Nonionic surfactants with parabens
• Phenols with ethanol

Correct Answer: Alkaloid salts with tannic acid

Q28. Co-administration of heparin and protamine in the same line results in:

• Enhanced anticoagulation
• Immediate neutralization and potential precipitation
• No interaction
• Oxidative degradation of protamine

Correct Answer: Immediate neutralization and potential precipitation

Q29. Before mixing two IV drugs with uncertain compatibility, the best first step is to:

• Proceed if solutions look clear
• Consult an evidence-based compatibility resource (e.g., Trissel’s, manufacturer data)
• Warm both solutions to body temperature
• Add extra diluent to reduce concentrations

Correct Answer: Consult an evidence-based compatibility resource (e.g., Trissel’s, manufacturer data)

Q30. How can a eutectic mixture be safely incorporated into a powder formulation?

• Mix eutectic-forming drugs directly without excipients
• Pre-mix each with absorbent (e.g., light magnesium carbonate) separately, then combine
• Add water to prevent liquefaction
• Increase trituration pressure to raise melting point

Correct Answer: Pre-mix each with absorbent (e.g., light magnesium carbonate) separately, then combine

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