Dissolution testing validation

The USP Dissolution General Chapter < 711 > describes the basket (Apparatus 1) and paddle (Apparatus 2) in detail. There are certain variations in usage of the apparatus that occur in the industry and are allowed with proper validation. The literature contains a recommendation for a new USP general chapter for dissolution testing (6). In this article, guidance for method validation and selection of equipment is described. It may be a useful guide when showing equipment equivalence to compendial equipment. 

In such cases, it is obviously advantageous to use biorelevant dissolution tests to characterize the drug substance, to compare formulations and to make a preliminary assessment of possible food effects. However, for routine quality control work, the manufacture of media containing bile components is not only rather time-consuming but may also present difficulties in terms of quality assurance and validation of the raw materials, as is the case with many chemicals obtained from natural sources. 

Sinkers can significantly influence the dissolution profile of a drug. Therefore, the use of sinkers should be part of the dissolution method validation. If equivalent sinkers are identified during the sinker evaluation and validation, the equivalent sinkers should be listed in the written dissolution test procedure. When a dissolution method utilizes a dissolution sinker and is transferred to another laboratory, the receiving laboratory should duplicate the validated sinker design(s) as closely as possible. 

Once the appropriate dissolution conditions have been established, the method should be validated for linearity, accuracy, precision, specificity, and robustness/ruggedness. This section will discuss these parameters only in relation to issues unique to dissolution testing. All dissolution testing must be performed on a calibrated dissolution apparatus meeting the mechanical and system suitability standards specified in the appropriate compendia. 

Validation of automated systems must demonstrate a lack of contamination or interference that might result from automated transfer, cleaning, or solution preparations procedures. Equivalency between the results generated from the manual method and the data generated from the automated system should be demonstrated. Since sensitivity to automated dissolution testing may be formulation related, qualification and validation of automated dissolution equipment needs to be established on a product-by-product basis (8,13) (see also Chapter 12 for a more detailed description of automation issues). 

Skoug JW, Halstead GW, Theis DI, Freeman JE, Fagan DT, Rohrs BR. Strategy for the development and validation of dissolution tests for solid oral dosage forms. Pharm Tech 1996 20(5) 58-72. 

Methods used to determine the performance characteristics of finished products fall into Category III. Dissolution tests (excluding measurement) and drug release tests are examples of these types of methods. Precision is the only parameter required for these methods according to the regulatory guidances, although all validation parameters may be determined based on the intent of the method. 

HPLC applications assays, impurity evaluation, dissolution testing, cleaning validation, high-throughput screening, and chiral separations (Chapters 13-18). 

In a recent study, Mirza et al. have pointed out that despite the obvious advantages, fiber-based dissolution studies are not yet implemented in industry. They have validated a fiber-optic based dissolution test for linearity, precision, accuracy, specificity and robusmess, with excellent results. 

UV-Vis spectroscopy Photoelectron spectroscopy X X Color measurement Dissolution testing Cleaning validation (ppm-level detection)... 

However, other analytical procedures, such as dissolution testing for dosage form or particle size determination for drug substance, are required for validation of analytical procedures. The revalidation of an analytical procedure is possible when, in particular circumstances, it could show changes in the synthesis of the drug substance, the composition of the finished product, or the analytical procedure. However, certain other changes may require validation as well. 

Solid oral dosage forms containing new chemical entities (NCEs) are commonly formulated into tablets or capsules as their first market image formulation. Subsequent drug product line extension development on these NCEs may evaluate more specialized drug delivery systems. Dissolution testing of standard oral tablets or capsules will commonly utilize the paddle or basket apparatus. In this chapter we focus primarily on the development and subsequent validation of dissolution testing methods that use these two devices. 

The validation requirements are discussed as they apply to both the sample preparation and sample analysis aspects of a dissolution method. The focus of the discussion in this chapter is on the validation considerations that are unique to a dissolution method. Validation is the assessment of the performance of a defined test method. The result of any successful validation exercise is a comprehensive set of data that will support the suitability of the test method for its intended use. To this end, execution of a validation exercise without a clearly defined plan can lead to many difficulties, including an incomplete or flawed set of validation data. Planning for the validation exercise must include the following determination of what performance characteristics to assess (i.e., strategy), how to assess each characteristic (i.e., experimental), and what minimum standard of performance is expected (i.e., criteria). The preparation of a validation protocol is highly recommended to clearly define the experiments and associated criteria. Validation of a test method must include experiments to assess both the sample preparation (i.e., sample dissolution) and the sample analysis. ICH Q2A [1] provides guidance for the validation characteristics of the dissolution test and is summarized in Table 4.1. 

Different approaches may be used to validate the sample preparation component of the dissolution test. However, it is important to understand that the objective of validation is to demonstrate that the procedure is suitable for its intended purpose. For example, one of the strategies will demonstrate the validity of different aspects of sample preparation during method development (prior to the formal method validation exercise). As a result, the final validation experiments will confirm the work done during method development. The strategy that will be followed for the method development and validation process will depend on the culture, expertise, and strategy of the analytical laboratory. 

Deaeration is a very important consideration in the development and validation of a dissolution test, as it can affect the rate of release of the drug substance from the dosage form. Ideally, a method should not be affected by the deaeration procedure. At a minimum, it should be demonstrated that some variability in the degree of deaeration will not significantly alter the results of the dissolution test. It should also be noted that media containing surfactants should not be deaerated, as that can result in excessive foaming. 

Rotational Speed. The rotational speed of a basket or paddle is an important consideration in the development and validation of the dissolution test. A speed of 100 rpm is commonly used with the basket apparatus and a speed of 50 rpm is used with paddles. In method validation, one needs to ensure that slight variations in rotational speed will not affect the outcome of the dissolution test. The compendial limit for variations in rotational speed is 4%, but a wider variation (e.g., 10%) may be considered in testing the robustness of the method. 

Effect of Non-USP Adaptation. The development and validation of the dissolution test for new formulations will often probe into the use of nonpharmacopoeia adaptations (e.g., peak vessel and unique sinker configurations). The suitability of these adaptations must be assessed during method development or validation. 

As mentioned earlier in the chapter, validation of the analytical component of the dissolution test will follow guidelines similar to those described in Chapter 2, where the validation parameters are discussed in detail. For the purposes of this chapter, only an overview is provided, with emphasis on the unique requirements of the dissolution test. 

The information in this chapter applies specifically to the first element sample preparation. The sample preparation steps are usually the most tedious and labor-intensive part of an analysis. By automating the sample preparation, a significant improvement in efficiency can be achieved. It is important to make sure that (1) suitable instrument qualification has been concluded successfully before initiation of automated sample preparation validation [2], (2) the operational reliability of the automated workstation is acceptable, (3) the analyte measurement procedure has been optimized (e.g., LC run conditions), and (4) appropriate training in use of the instrument has been provided to the operator(s). The equipment used to perform automated sample preparation can be purchased as off-the-shelf units that are precustomized, or it can be built by the laboratory in conjunction with a vendor (custom-designed system). Off-the-shelf workstations for fully automated dissolution testing, automated assay, and content uniformity testing are available from a variety of suppliers, such as Zymark (www.zymark.com) and Sotax (www.sotax.com). These workstations are very well represented in the pharmaceutical industry and are all based on the same functional requirements and basic principles. 

---