Clay and non-clay minerals in the pharmaceutical industry: Part I. Excipients and medical applications

Minerals are widely used in the pharmaceutical industry as lubricants, desiccants, disintegrants, diluents, binders, pigments and opacifiers, as well as emulsifying, thickening, isotonic agents, and anticaking agents, and flavour correctors and carriers of active ingredients.A variety of minerals are used as excipients in pharmaceutical preparations because they have certain desirable physical and physico-chemical properties, such as high adsorption capacity, specific surface area, swelling capacity, and reactivity to acids. Other important properties are water solubility and dispersivity, hygroscopicity, unctuosity, thixotropy, slightly alkaline reaction (pH), plasticity, opacity, and colour. Clearly such minerals must not be toxic to humans. The following minerals are commonly used as excipients: oxides (rutile, zincite, periclase, hematite, maghemite, magnetite), hydroxides (goethite), carbonates (calcite, magnesite), sulfates (gypsum, anhydrite), chlorides (halite, sylvite), phosphates (hydroxyapatite), and phyllosilicates (palygorskite, sepiolite, kaolinite, talc, montmorillonite, saponite and hectorite). More recently, some tectosilicates (zeolites) also feature in pharmaceutical preparations.Minerals also enjoy the following medical/health applications: a) contrast diagnostic techniques, b) production of dental cements and dental molds in odontology, c) immobilization of limbs and fractures or dental and craniofacial surgical procedures in traumatology, d) bone grafts or construction of orbital implants, and e) spas and aesthetic centers. Examples of such minerals are oxides (zincite, magnetite and maghemite), sulphates (gypsum and barite), phosphates (hydroxyapatite) and phyllosilicates (clay minerals).