Determination and characterization of metronidazole–kaolin interaction
, Fadilah Sfouq Aleanizy , Fulwah Alqahtani , Omaimah Al Gohary , Eram El Tahir , Rania Al Shalabi . 2014
The needs for safe, therapeutically effective antidiarrheal combination continuously lead
to effective treatment. When administered simultaneously, metronidazole–kaolin interactions have
been reported by FDA but not studied. This paper is the first to study metronidazole–kaolin interactions.
Adsorption isotherms of a metronidazole–kaolin antidiarrheal combination from aqueous
solutions at an in vivo simulated pH conditions were obtained at 37± 0.5 C. Langmuir constants
for the adsorption are 10.8225, 41.3223 mg g1 and 11.60, 2.56 l g1 aimed at the monolayer capacity,
and the equilibrium constant at pH 1.2 and 6.8, respectively. pH effect on adsorption of known
concentration of metronidazole by kaolin was also studied over the range 1.2–8. A gradual increase
in the adsorbed amount was noted with increasing the pH. Elution studies by different eluents
showed that drug recovery from adsorbent surface was pH-dependent via competitive mechanism.
The elution followed the sequence: 0.1 M HCl > 0.1 M NaCl > H2O. Adsorption–desorption
studies revealed physical adsorption. The equilibrium concentration of metronidazole decreased
as the adsorbent concentration was increased in the systems.
The dissolution profiles (USP) of commercially available tablets (Riazole 500 mg) were obtained
alone and in the presence of either (ORS) rehydration salts and 9 or 18 g of kaolin powder. The
percentage drug released versus time: 95.01% in 25 min, 101.02% in 30 min, 67.63% in 60 min,
60.59% in 60 min, respectively.
The percentage drug released versus time was increased with ORS due to common ion effect
[Cl], while, it was decreased with kaolin due to adsorption. The mechanism of reaction of
Riazole (500 mg) tablets in the different dissolution media, confirms with Korsmeyer–Peppas
model.
