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Guidance on Formulating Semisolid Drugs size than expected and thereby raised questions about the product efficacy. In addition to ingredient solubility and particle size, other physical characteristics and specifications for both ingredients and finished products are important.

The subjects covered here are generally applicable to all forms of topical drug products, including those that are intended to be sterile. The topics given below address several problem areas that may be encountered in the production of semisolid drug products (including transdermal products) including their potency, active ingredient uniformity, physical characteristics, microbial purity, and chemical purity.

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EQUIPMENT AND PRODUCTION CONTROL

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When validating a suspension manufacturing process, determine how to ensure that the product remains homogeneous during the filling process and establish the data that support the adequacy of the firm’s process. When the batch size is large and the bulk suspension is in large tanks, determine how the low levels of bulk suspension near the end of the filling process are handled. If the bulk suspension drops
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Handbook of Pharmaceutical Manufacturing Formulations: Semisolid Products

below a level, can this be adequately mixed? This question must be answered. If the residual material transferred to a smaller tank, how is the reliance made on handmixing of the residual material? The adequacy of the process for dealing with residual material should be demonstrated.

It is therefore important that the following considerations be adequately addressed in a cleaning validation protocol and in the procedures that are established for production batches.

A. DETAILED CLEANING PROCEDURES C. PROCESS TEMPERATURE CONTROL
Typically, heat is applied in the manufacture of topical products to facilitate mixing or filling operations. Heat may also be generated by the action of high-energy mixers. It is important to control the temperature within specified parameters, not only to facilitate those operations but also to ensure that product stability is not adversely