Accurate percent moisture content is essential for maintaining the stability of drug products. If a product is too moist or too dry, it may not be suitable to be administered and will not exert the desired therapeutic effect. Most of pharmaceutical products contain moisture. The percent moisture content is seldom of interest. Rather, it shows whether a product intended for trade and production has standard characteristics such as storage ability, agglomeration, microbiological stability, flow properties, viscosity, etc. The dry substance content, concentration or purity, compliance with quality agreements, the therapeutic value of the product, and legal conformity are other important issues. In addition, the determination of moisture content has the following applications:
(i) Freshness: Fresh products has specified characteristic features. Moisture induces changes in the state of solid. As they age and begin to degrade, some dry out and some pick-up excess moisture and begin to mold.
(ii) Labeling: Pharmaceutical industries require a minimum or maximum percentage of moisture in certain products in order for them to be packaged and labelled. If they don’t fit to these standards, the products cannot pass the quality standards and unfit for commercial release. For example, freeze dried products, hard gelatine capsules
etc.
(iii) Cost: In processed pharmaceutical products, the percentage of water can determine its final price. Generally, a product with more water will cost less.
(iv) Processing: The moisture has effect on the performance of excipients thus manufacturers and physicians need to know the moisture content of product to ensure that it is processed and packaged in a safe, stable way.
(v) Quality: Moisture content determines the way most product appropriate to administer, taste, feel and look. It is one of the important ways to measure product quality.
(vi) Shelf life: The physicochemical stability of bioactive agents alone and in combination with excipients is affected by moisture. Thus, shelf life of product depends on its moisture content at the time of packaging and rate of moisture gain
during storage. Stability of products depends upon the per cent moisture in finished products.
Equilibrium moisture content