Natural zeolites for pharmaceutical formulations: Preparation and evaluation of a clinoptilolite-based material

Aim of this work was the preparation, starting from a clinoptilolite-rich rock, of a material suitable for the development of pharmaceuticals. In particular, the purpose was to obtain a reproducible product that maximizes zeolite properties and minimizes any kind of interference chemical, mineralogical and microbiological. In evaluating the material for the planned use, the recommendations and procedures of European, US and Japanese Pharmacopoeias were taken as benchmark to the largest extent possible. A set of technological properties was also determined. The prepared material, containing approximate to 90 wt.% of Na-clinoptilolite, was obtained through a replicable process, and do not contains fibrous minerals classified as carcinogenic by the IARC. Chemical analyses evidenced contents of trace metals below the more restrictive limits established by Eur Ph., USP and JP for "bentonite" - taken as reference due to the similarities between smectites and zeolites, and because of the lack of a Monograph on clinoptilolite. The oral bioaccessibility of potential harmful elements, tested simulating the transit in the gastrointestinal tract according to Eur Ph., was three to six orders of magnitude lower than the permissible daily exposure established by USP. The microbiological quality of the material complied with the acceptance criteria of Eur Ph. The clinoptilolite structure was not significantly affected by sterilization process nor by simulated gastric juices. As concerns the characteristics determined, the prepared material is suitable for the development of systems exploiting clinoptilolite's properties as pharmaceutical excipient.