Determine pA2 Value of a Marketed Formulation Hosciamine Butybromide (Hb) On Chick Intestine Preparation by Schild Plot Methods

Background: Hyoscine Butylbromide (HB) is a competitive antimuscarinic agent. It’s widely used for the treatment of gastrointestinal smooth muscle spasms. The present study aimed to determine the antagonist potency of HB using the isolated chick intestine using the Schild plot method. Methods: Fresh chick intestine was mounted in a 30 mL organ bath containing Tyrode's solution at 37°C. Acetylcholine induced contractions were recorded before and after administration of increasing concentrations of HB. The percentage inhibition of response was calculated, and a shield plot was constructed to estimate the pA₂ value. Results: Acetylcholine produced graded response curve, while HB caused a reversible, concentration dependent inhibition. Approximately 50% inhibition of the acetylcholine response was observed at an HB concentration of 96.28 µg/mL. The isolated chick intestinal preparation was proven to be a sensitive tissue preparation for evaluating the muscarinic antagonism of HB. Conclusion: Hyoscine Butylbromide exhibited antimuscarinic activity. The Hyoscine Butylbromide (HB) effect as an antagonistic or inhibitory response on acetylcholine induced contractions in isolated chick intestine using the Schild plot method.