Most substances used in drugs today are hygroscopic and any absorption of moisture during the manufacturing process will affect the final weight, quality and durability.
When hygroscopic ingredients are weighed and mixed, it is important that the products’ weight is not influenced by absorption of moisture from the surrounding air.
In powder form, moisture will affect the flow, caking, compaction and strength properties of the manufactured solid form.
Yeast, moulds and bacteria require a certain amount of moisture to support growth. Controlling relative humidity is probably one of the most important factors in maintaining a sterile environment.
A cool dry environment generally enables faster production, a better quality product and a longer shelf life. The majority of tableting processes require humidity control between 20 and 35%RH at 21 to 24°C.