Hyoscine n-butylbromide (Buscopan) is an anticholinergic agent that has been used as a muscle relaxant for the barium enema examination as well as for CT and MR colonography in Europe. It has not received approval for use in the USA. Buscopan has a different mechanism of action than glucagon and is less expensive. Hypotonia of the colon is induced by its action on the postganglionic parasympathetic receptors in smooth muscle. Contraindications to the use of anticholinergic agents include glaucoma, severe prostatic hyperplasia, unstable heart disease, bowel obstruction or ileus, and myasthenia gravis. Anticholinergics can cause side effects such as tachycardia, dry mouth, acute urinary retention, and acute gastric dilatation.
In a study comparing various antispasmodic agents for barium enema, 106 patients received a placebo, 109 patients received 1 mg intravenous glucagon, and 109 patients received 20 mg intravenous Buscopan prior to the enema (Goei et al. 1995). Results showed that Buscopan performed better than glucagon for colonic distension, although about 5% of patients who received Buscopan experienced blurry vision. The routine use of Buscopan for CT colonography is controversial. In a study of 73 patients undergoing CT colonography, 36 patients received 20 mg of Buscopan intravenously and 37 subjects received no muscle relaxant immediately prior to scanning. Intravenous Buscopan was not found to improve the adequacy of colonic distension, and there was no significant improvement in the accuracy of polyp detection (Rogalla et al. 2005). It was concluded that the routine use of intravenous Buscopan for CT colonography was not supported. Another study performed on 136 patients randomized subjects to receive either 20 mg or 40 mg of Buscopan or no muscle relaxant prior to CT colonography (Bruzzi et al. 2003). Significantly improved distension was found in the cecum and in the ascending and transverse colon in the supine position and in the ascending and descending colon in the prone position. No incremental advantage was found with the larger dose of 40 mg. This study also found that the use of a rectal balloon catheter did not improve distension. A recently published study compared patients not receiving an anti-spasmodic agent with patients receiving 1 mg of glucagon intravenously and subjects receiving 20 mg of Buscopan intravenously immediately prior to supine-only CT colonography.(TAYLOR et al. 2003). Mean colon volumes and radial distensibility were significantly better with Buscopan only when comparing patients who received Buscopan with patients who did not receive any muscle relaxant. The value of Buscopan for CT colonography using dual positioning remains controversial.
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