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Sodium alginate in film coating

Q: How do you use sodium alginate in the film coating of tablets? What kind of formulation could be used for 100 Kg of tablets?

A: Fred Rowley replies:

Sodium alginate has many industrial uses and has made a successful jump from seaweed to human society. For the coating of tablets, sodium alginate is an alternative to hydroxypropyl methylcellulose (HPMC) and other cellulose-based coatings available today. It hydrates readily in water, and forms clear, glossy, uniform films. This material is customarily used as part of a controlled release matrix.

To the specific question: Sodium alginate may be used in an aqueous media between 15% and 20% by weight and coated to a weight gain of 2.0% to 3.5%. There are many vendors producing this material and there are many formulas available. For a 100-kg batch, one would place 4 kg sodium alginate in 100 kg of water, along with other items (color/plasticizer, etc). You would then spray the mixture onto the tablets until a weight gain of between 2% and 3.5% is achieved.