Effervescent tablets and powders are produced in much the same manner as conventional tablets and powders, but production must occur in very low humidity areas. Effervescent granulations can be mixed in conventional blending equipment, such as ribbon, twin-cone, and V-type blenders. All equipment should be well grounded and should allow you to make it completely and absolutely dry after wash-down. Any traces of moisture in the equipment will give erratic granulation results and most likely result in lost batches of product. Figure 1 shows a tablet press making an effervescent dosage. Wet granulation of the effervescent base can be performed by carefully adding 0.1 to 1.0 percent water (weight-to-weight basis) to the chosen blending equipment. The granulation steps must be precisely timed and the ingredients mixed thoroughly to distribute the solvent or binder solution evenly in the blend. The mix is then quickly discharged to drying ovens. It must constantly monitor the operational parameters of all equipment, especially drying equipment, as variations in drying times and temperatures can affect the finished product. While stable granulations will ultimately be made, vast differences in tablet hardness and disintegration times can result from over- or under-reacting the granulation. After drying, the granulation is sized, and a final mix is performed. Fluid-bed dryers have been used for many years to make effervescent granulations. Basically, the water or binder solution is sprayed onto the effervescent mixture while it is suspended in a stream of hot, dry air. The humidity and temperature of the air serve to stop the effervescent reaction quickly and uniformly.
To ensure that you produce a free-flowing granulation, chose the particle sizes carefully and monitor all systems closely. Vacuum granulators have also been used to make effervescent granulations. This equipment gives you a very controlled granulation of the product and allows a dust free environment. The equipment also generally requires less power and less operating space than other types of granulators. In operation, the water or binder solution is sprayed onto the effervescent mixture during blending. Drying occurs by placing the granulation under vacuum and heating it via a thermal jacket. Effervescent products normally require tablet presses that can deliver high compression forces. If the tablets are to be wrapped in foil or placed into a tube, give careful attention to the tablet parameters during compression. Monitor the tablet thickness to ensure the wrapping or packaging equipment can handle the tablets. Strict control of temperature and humidity in all areas is a must (65 to 75ºF, relative humidity of 10 percent), or the formulation will begin a chemical reaction after it’s packaged. In essence, the tablet will self-destruct because the byproducts of an effervescent reaction are water and carbon dioxide. The best way to stabilize an effervescent product is to produce it in an environment where humidity is under strict control and to package it in a suitable moisture barrier. All ingredients in the formulation must be anhydrous. Your contractor should test for free moisture before packaging.