In an attempt to achieve sustained action for the oral administration of terbutaline sulfate (TBL)​, its surface-​reversible interaction with several clays such as saponite, bentonite, attapulgite and laponite was studied.  Adsorption studies indicated that, saponite showed the greatest adsorption of the drug among the tested clays.  The max. adsorption occurred at pH 7.  The cationic exchange was considered as the main mechanism responsible for interaction between the drug and clays.  The drug-​saponite sorbate showed slight retardation of drug dissoln.  Successful sustained release formulation of the drug was achieved by microencapsulation of the drug sorbate using cellulose acetate butyrate as coating material.  Sustained bronchodilator responses after administration of this double-​barrier formulation was confirmed in patients suffering from reversible chronic air flow obstruction.