What is the dissolution method for oral suspension?

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Prof. Sudipta Roy's picture


In general, the rotating paddle method using an adequate dissolution medium is the recommended method for dissolution.To obtain representative samples, product preparation should follow standardized procedures based on shaking or mixing. Method parameters such as sample introduction and agitation rate should be established on the basis of the viscosity and composition of the suspension matrix.

The sample introduction technique must be accurate,precise and reproducible. Even though oral suspensions of any viscosity would be exposed to similar ranges of shearing forces after administration in vivo,the in vitro agitation rate should be selected to facilitate discrimination between batches with different release properties.

For low viscosity suspensions, an accurate dose can be delivered to the bottom of the dissolution vessel using a volumetric pipette. A slow agitation of 25rpm is generally recommended for less viscous suspensions1.

For high viscosity samples, the dose may be determined by weight with a quantitative sample transfer to the dissolution vessel to ensure accuracy of the sample size introduced. High-viscosity suspensions may also require a faster agitation rate such as 50 or 75rpm to prevent sample mounding at the bottom of the vessel.

Ideally, sample weight/volume should reflect a typical dose of the product. However, testing a partial dose - for instance-10% to 20% of the usual product dose - is recommended rather than using a surfactant to obtain sink conditions.


1. USP 24/NF 19 (2000) United States Pharmacopoeal Convention (USPC) Inc.,

12601 Twinbrook Parkway, Rockville, MD 20852.

2.British Pharmacopoeia, HMSO, London. (1998).

sudipta roy


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