27+ Interview Questions With Answers On Dissolution Test
Prepare for pharmaceutical interviews with these 25+ essential dissolution test questions and answers. Covers USP apparatus, testing procedures, sink conditions, and more.
1. What is a dissolution test in pharmaceuticals?
Answer: A dissolution test measures the rate and extent to which the active pharmaceutical ingredient (API) is released from a solid dosage form (e.g., tablet, capsule) into a dissolution medium under standardised conditions.
2. Why is dissolution testing important?
Answer: It ensures batch-to-batch consistency, helps predict drug bioavailability, and is a critical quality control parameter for regulatory approval and product performance.
3. What apparatuses are used for dissolution testing?
Answer: The USP recommends several apparatuses, primarily:
- Apparatus 1: Basket
- Apparatus 2: Paddle
- Apparatus 3: Reciprocating Cylinder
- Apparatus 4: Flow-through Cell
- Apparatus 5–7 for specialized testing
4. What is the most commonly used apparatus?
Answer: Apparatus 2 (Paddle) is most commonly used for tablets, while Apparatus 1 (Basket) is often used for capsules.
5. What is the typical dissolution medium volume?
Answer: Usually, 500 mL to 1000 mL of medium is used, depending on the product and regulatory guidelines.
6. What are sink conditions in dissolution?
Answer: Sink conditions exist when the volume of medium is at least 3 times greater than the volume required to completely dissolve the drug substance.
7. What factors affect the dissolution rate?
Answer:
- Surface area of the drug
- Agitation speed
- Solubility
- pH and composition of the medium
- Temperature
- Presence of excipients
8. What is the standard temperature for dissolution testing?
Answer: 37 ± 0.5°C, which simulates human body temperature.
9. How is the sample collected during the test?
Answer: Samples are withdrawn at specified time points, filtered, and analysed, often using UV spectrophotometry or HPLC.
10. What is the significance of RPM in dissolution?
Answer: RPM (revolutions per minute) determines the agitation speed. It affects the rate of dissolution by influencing the hydrodynamic conditions around the dosage form.
11. What is the Q value in dissolution?
Answer: The Q value is the amount (%) of drug that must dissolve within a specified time, as defined by the pharmacopoeia (e.g., 80% in 30 minutes).
12. How do you prepare a dissolution medium?
Answer: The medium (e.g., 0.1 N HCl, phosphate buffer) is prepared using purified water, adjusted to the desired pH, degassed, and equilibrated to 37°C.
13. Why is degassing of the medium important?
Answer: Dissolved gases, especially air, can form bubbles on the dosage form or apparatus, interfering with the test’s accuracy and reproducibility.
14. What are the common media used in dissolution tests?
Answer:
- 0.1N HCl
- Simulated gastric fluid (SGF)
- Simulated intestinal fluid (SIF)
- Phosphate buffer (pH 6.8 or 7.4)
- Water
15. What is the role of surfactants in dissolution?
Answer: Surfactants like SLS (sodium lauryl sulfate) are used to enhance the solubility of poorly soluble drugs in the medium.
16. What is a discriminatory dissolution method?
Answer: A method capable of detecting changes in critical formulation and process parameters that may impact the in vivo performance of the drug.
17. What is the difference between single-point and multi-point dissolution testing?
Answer: Single-point tests check drug release at one time point (e.g., 30 min), while multi-point tests assess release profiles over time (e.g., 5, 10, 15, 30, 45 min).
18. What is the calibration requirement for the dissolution apparatus?
Answer: The apparatus must be calibrated using a Performance Verification Test (PVT) with USP calibrator tablets to ensure accuracy and precision.
19. What are the acceptance criteria for dissolution testing?
Answer:
Generally:
- Stage 1 (S1): All 6 units ≥ Q + 5%
- Stage 2 (S2): 12 units; average ≥ Q, none < Q − 15%
- (Based on USP/ICH guidelines)
20. How is the result of a dissolution test analysed?
Answer: The % release is plotted over time and compared with reference standards or innovator products to evaluate performance.
21. What are the common issues during dissolution testing?
Answer:
- Coning or capping of dosage forms
- Air bubbles
- Improper RPM
- Non-sink conditions
- Evaporation or pH drift
22. What is dissolution profile comparison (f2 test)?
Answer: An f2 value (similarity factor) of 50–100 suggests that two dissolution profiles are similar, commonly used in generic-drug comparison.
23. What is the significance of IVIVC in dissolution?
Answer: IVIVC (In Vitro-In Vivo Correlation) predicts in vivo drug release from in vitro dissolution data, used in formulation development and biowaiver applications.
24. What is the difference between dissolution and disintegration?
Answer:
- Disintegration: Time taken for a tablet to break into smaller particles
- Dissolution: Rate and extent to which API goes into solution
25. How do you validate a dissolution method?
Answer: By assessing specificity, linearity, accuracy, precision, robustness, and solution stability using ICH guidelines.
26. What are S1, S2, and S3 in dissolution?
S1, S2, and S3 are stages in the dissolution acceptance criteria defined by USP pharmacopeias to ensure consistent drug release:
- S1 (Stage 1): Test 6 units. All must release not less than Q + 5%. If passed, no further testing is needed.
- S2 (Stage 2): If S1 fails, test 6 more units (total 12). Average must be ≥ Q, and no unit < Q − 15%.
- S3 (Stage 3): If S2 fails, test 12 more units (total 24). Not more than 2 units < Q − 15%, and none < Q − 25%.
Q = specified amount of drug (usually % released) in a given time.
27. Why is 900 mL of Media used in a dissolution test?
In dissolution testing, 900 mL of medium is commonly used to maintain sink conditions, ensuring the drug dissolves in a volume large enough that its concentration stays well below saturation. This mimics in vivo conditions, where drugs are diluted by body fluids. A larger volume also minimizes the impact of variability in solubility or apparatus performance, leading to more consistent and reliable results.
28. What are “Q” and “Q+5%” in Dissolution?
In dissolution testing, “Q” is the specified amount (usually in %) of drug that must dissolve in the given time, as defined by pharmacopeial standards (e.g., 80% in 30 minutes).
“Q + 5%” means the drug release must be at least 5% more than the Q value, used in Stage 1 (S1) to ensure stricter acceptance criteria. For example, if Q = 80%, then Q + 5% = 85%.
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Further Reading