In order to protect protein and peptide drugs against inactivation by different barriers in the gastro-intestinal tract and to improve their absorption, alginate microparticles as a carrier Of L-lactate dehydrogenase, were developed by spray-drying technique. However, alginate complexation and spray-drying conditions led to enzyme activity loss. Such a drawback was overcome by using protectant additives (carboxymethylcellulose sodium salt, polyacrylic acid sodium salt, lactose) preventing the enzyme inactivation by both interaction with alginate and experimental conditions, lactose having the most protective effect. Nevertheless, only polyacrylic acid sodium salt provided a microparticulate structure required for the target of the Peyer's patches. (C) 2002 Elsevier Science B.V. All rights reserved.