Efficacy of Attapulgite Clay as Adsorbent for Metronidazole Drug Overdose in vitro.

Abstract

Surface active materials have many applications in medicine. Attapulgite clay
used in medicine as antidiarrheal, and as additives in some pharmaceutical
formulations. Metronidazole drug is widely used as antiprotozoal drug in the treatment
of amoebic dysentery and amoebic liver abscess. Drug overdose may treated by
adsorbents especially by activated charcoal suspension to prevent further absorption,
but usually it is unacceptable to drink. Hence, in this work a study was carried out to
estimate the ability of attapulgite clay as adsorbent for metronidazole overdose in vitro
as a possible alternative for activated charcoal.
The change in the concentration of metronidazole after incubation of known
concentration of aqueous metronidazole solutions with attapulgite was measured as
the adsorbed quantity. UV-Visible spectrophotometry technique was used to follow
the quantity of the adsorbed drug. The adsorption also occurred in 0.1N HCl solution
to simulate the acidity of the stomach. The adsorption experiments were repeated at
(12, 25, 37.5, and 50ºC) to measure the thermodynamical parameters (ΔHº, ΔGº, ΔSº).
Adsorption of metronidazole on attapulgite obeyed Freundlich adsorption
isotherm of S2 type according to Giles classification of adsorption isotherm in
solution. The maximum quantity adsorbed tends to be slightly increased in acidic
medium (0.1N HCl) especially at low concentration of the drug. The thermodynamic
parameters values were (ΔHº=-19.86 KJ.mol-1, ΔGº=-17.994
KJ.mol-1, and ΔSº=6.25 J.mol-1ºK-1).
Metronidazole drug can be adsorbed by attapulgite clay surface at low
concentration of the drug and the quantity of the adsorbed drug increased with
increasing the initial concentration of the drug. The adsorption quantities were
decreased with increasing temperature indicating an exothermic adsorption process
which also reinforced by the values of thermodynamic parameters. Acidity has a slight
effect on adsorption.
Keywords: Metronidazole, attapulgite, adsorption, drug overdose, ΔHº, ΔGº, ΔSº.