Acid–base equilibria of tetracycline in sodium montmorillonite suspensions

Interaction between tetracycline and smectite in aqueous solution

“…Thus, the net effect of adding smectite to TC solution would be equivalent to shifting the pK a1 to a higher pH value as observed by Browne et al [20]. In their original experiment [20] a dilute montmorillonite suspension, with a solid to liquid ratio of 1:100 in Na form, was comparable to this study of 1:200. However, the initial TC concentration they used was much lower (200 mg/L) in contrast to up to 3000 mg/L used in this study.…”

“…These pH values would be similar to the effective pK a1 value of TC in the presence of different types of smectite. Also, the effective pK a1 for TC in the presence of SWy-2 was lower than 6.23 for Na-montmorillonite as reported by Browne et al [20].…”

Adsorption of Melted Drugs Onto Smectite

“…Its use as a drug carrier is widely studied, as the location of the drug molecules within the interlayer space of the clay may modify the suitability of some drugs for biological use (Grim 1962;Theng 1974;Grim and Gtiven 1978;Porubcan et al 1979;Browne et al 1980;Hermosfn et al 1981;White and Hem 1983;Forteza et al 1989). Usually, intercalation is achieved by adsorption from aqueous solutions of the drug, but some authors have recently reported on alternative methods that are faster, cleaner and cheaper, such as mechanically grinding a mixture of the drug and the clay (Vicente et al 1989;Ogawa et al 1989Ogawa et al , 1990aOgawa et al , 1990bOgawa et al , 1991.…”

Gastroretentive montmorillonite-tetracycline nanoclay for the treatment of Helicobacter pylori infection

“…It exists predominantly as a cation at pH <3.3, zwitterion at a pH between 3.3 and 7.7, and anion at pH >7.7 (Browne et al, 1980;Porubcan et al, 1977;Wang et al, 2010). Surface interactions (cation bridging, complexation, hydrogen bondings, van der Waals interactions), and/or cation exchange upon contact with MM were described in the literature, even if more research is needed to better understand the reaction process (Parolo et al, 2010(Parolo et al, , 2008Wang et al, 2010).…”

“…Adsorption of tetracyclines onto soils and clay minerals were conducted as early as 1950's even if to a limited extent. To date these studies focused on removal TC as an organic contaminant of water or soils to improve environmental quality (Aristilde et al, 2013;Avisar et al, 2009;Chang et al, 2009;Wang et al, 2010), and on biopharmaceuticals effects due to the coadministration of TC and clays acting as suspending agents (Browne et al, 1980;Porubcan et al, 1977), or topical excipients (Parolo et al, 2010). Conversely, clays have not been hitherto object of study for the development of a gastroretentive TC delivery system.…”