Inorganically modified diatomite as a potential prolonged-release drug carrier

• Inorganic modification of diatomite improved adsorption of diclofenac sodium.
• Comprimates containing the adsorbed drug in near therapeutic dose were prepared.
• Prolonged drug release from comprimates containing the adsorbed drug was achieved.
• Drug-modified diatomite physical mixture also demonstrated prolonged drug release.

Inorganic modification of diatomite was performed with the precipitation product of partially neutralized aluminum sulfate solution at three different mass ratios. The starting and the modified diatomites were characterized by SEM–EDS, FTIR, thermal analysis and zeta potential measurements and evaluated for drug loading capacity in adsorption batch experiments using diclofenac sodium (DS) as a model drug. In vitro drug release studies were performed in phosphate buffer pH 6.8 from comprimates containing: the drug adsorbed onto the selected modified diatomite sample (DAMD), physical mixture of the drug with the selected modified diatomite sample (PMDMD) and physical mixture of the drug with the starting diatomite (PMDD). In vivo acute toxicity testing of the modified diatomite samples was performed on mice.High adsorbent loading of the selected modified diatomite sample (~ 250 mg/g in 2 h) enabled the preparation of comprimates containing adsorbed DS in the amount near to its therapeutic dose. Drug release studies demonstrated prolonged release of DS over a period of 8 h from both DAMD comprimates (18% after 8 h) and PMDMD comprimates (45% after 8 h). The release kinetics for DAMD and PMDMD comprimates fitted well with Korsmeyer–Peppas and Bhaskar models, indicating that the release mechanism was a combination of non-Fickian diffusion and ion exchange process.