Effervescent formulation binders

The use of a binder in effervescent formulations is limited by the fact that any binder, even if water soluble, will retard the tablet disintegration. Therefore, the amount of binder in a given formula will be a compromise between desired granule strength and desired disintegration time. 

Binders for dry granulation, such as lactose, mannitol, dextrose, are almost inappropriate, because they would be effective only in larger amount than that allowed by an effervescent formulations. The binder choice in wet granulation is also limited by the method of production and consequently by the amount of granulating liquid. 

Effervescents comprise a soluble organic acid and an alkali metal carbonate salt. Citric acid is most commonly used for its flavor-enhancing properties. Malic acid imparts a smoother after taste and fumaric, ascorbic, adipic, and tartaric acids are less commonly used [14], Sodium bicarbonate is the most common alkali, but potassium bicarbonate can be used if sodium levels are a potential issue with the formulation. Both sodium and potassium carbonate can also be employed. Other excipients include water-soluble binders such as dextrose or lactose, and binder levels are kept to a minimum to avoid retardation of disintegration. All ingredients must be anhydrous to prevent the components within the formulation reacting with each other during storage. 

The use of binders will normally prevent a rapid dissolution of the effervescent tablet. Therefore, many effervescent tablets are formulated without any binder. However, effervescent granules may be formulated with binders since their large surface area, when compared withthat of the conventional or the effervescent tablet, will result in rapid dissolution. An effervescent... 

Povidone K 25 and povidone K 30 are very good binders for effervescent tablets, as they dissolve rapidly in water to form a clear solution. This particularly applies to effervescent vitamin tablets, e.g. ascorbic acid tablets [368 b]. Tables 65 and 66 give formulations for ranitidine effervescent tablets and multivitamin effervescent tablets as typical examples that were developed on a laboratory scale. For the granulation of multivitamin preparations, it is always preferable to use a fluidized bed. 

As far as other exdpients, such as diluents or binders, are concerned there is a very little freedom for the formulator to experiment, because of the large dimension of the tablet required for effervescent systems. In addition, compressibility caimot be enhanced by additional binders for effervescent dosage form, because of the larger size of the tablet. 

I.3.2. Process with Alcohol or Hydroalcoholic Solution. As reported in the previous example, it is sometimes preferable to granulate with a hydroalcoholic solution to initiate a lighter effervescence so as to keep the reaction under better control during the process. Use of alcohols is indispensable in case a binder like PVP is included in the formulation. In fact, the amount of water required to dissolve PVP to obtain the binding action will be too high, and it will not be possible to keep the effervescent reaction under control. 

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