When a patient swallows a tablet, it needs to dissolve at the right rate in the right place to be effective. Too slow, and the drug isn't absorbed. Too fast, and the dose may cause side effects. Tablet dissolution testing is the in-vitro method pharmaceutical companies use to verify and control this critical behaviour — and regulatory agencies worldwide require it.
What is Dissolution Testing?
Dissolution testing measures the rate and extent to which an active pharmaceutical ingredient (API) is released from a tablet or capsule into a liquid medium under controlled conditions. It simulates — in a simplified way — what happens when a tablet dissolves in the human gastrointestinal tract.
The test is used at every stage of the product lifecycle: during formulation development, for batch release, and throughout stability studies.
USP Apparatus 1 and Apparatus 2 — What's the Difference?
The two most commonly used dissolution methods, defined in USP <711> and EP 2.9.3, are:
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Apparatus 1 (Basket Method):
The tablet is placed inside a wire mesh basket that rotates in the dissolution vessel. Used for tablets that tend to float or disintegrate slowly.
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Apparatus 2 (Paddle Method):
A paddle stirs the dissolution medium while the tablet sinks to the bottom of the vessel. The most widely used method — simpler and more versatile for most solid dosage forms.
Key Test Parameters
Precise control of test conditions is essential for reproducible, regulatory-acceptable results. The key parameters are:
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Temperature:
37.0°C ± 0.5°C (body temperature) — maintained by a water bath
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Rotation Speed:
Typically 50 or 75 RPM for paddle; 100 RPM for basket
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Dissolution Medium:
Simulated gastric or intestinal fluid, or specified buffer
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Sampling Time Points:
Defined per product monograph (e.g., 15, 30, 45, 60 minutes)
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Number of Vessels:
Minimum 6 vessels per run (USP requirement)
What to Look for in a Dissolution Tester
When selecting a dissolution apparatus for your lab, check for these features:
- Temperature accuracy of ±0.2°C or better
- Speed accuracy of ±1 RPM
- Individual vessel monitoring (each vessel independently controlled)
- 21 CFR Part 11 compliant software with audit trail
- IQ/OQ documentation support for regulatory validation
Raise Lab Equipment's RLTDT series dissolution testers meet USP <711>, EP 2.9.3, and IP requirements and are available in 6-vessel and 8-vessel configurations. The instruments feature precision temperature control, individual vessel monitoring, and full data logging for GMP compliance.
Dissolution vs. Disintegration — A Common Confusion
Disintegration tests whether a tablet physically breaks apart. Dissolution tests whether the drug actually dissolves and becomes available for absorption. Both tests are required — but they measure different things. A tablet can disintegrate quickly yet dissolve slowly if the API has poor solubility.
For complete quality control of solid dosage forms, both tests should be part of your standard QC protocol.
Acceptance Criteria (Q value): Most USP monographs require at least 80% of the labelled drug to dissolve within 30 minutes (Q = 80%). Your dissolution tester must maintain all parameters within tolerance to produce valid data.