Journal of Gastroenterology and Hepatology (1999) 14, 1219–1222 aftertaste and oily texture are disliked by most patients. 2,9–11 There are very few prospective studies analysing the efficacy of castor oil for colonoscopy in the literature. 12 Whether castor oil is more likely to cause abdominal cramping, dehydration and electrolyte disturbance is unclear. Magnesium citrate, a saline laxative, can induce retention of fluid in the small bowel because of its osmotic effect. 13 This fluid then enters the proximal colon and flushes the faecal materials from the colon. A bowel evacuant kit (magnesium citrate oral solution, phenolphthalein tablets and a bisacodyl sup- pository) was reported to have the same cleansing effi- cacy, and induce less discomfort, when compared with castor oil used for colonic examinations. 10 It is also INTRODUCTION A clean colon preparation prior to endoscopy or X-ray examination is essential to obtain an accurate diagno- sis, as residual faecal material may hide colonic lesions, such as early colon carcinoma and polyps. 1 Moreover, an inadequate colon preparation often requires repeated examination, which results in inconvenience and cost to the patients. The various colon cleansing regimens include castor oil, magnesium citrate, bisacodyl tablets, senna extract, mannitol, polyethylene glycol lavage and others. 2–8 Castor oil, which acts on both the small and large intestines, is commonly employed as a preparation for radiological examination and colonoscopy, but its 3-D ENDOSCOPIC ULTRASONOGRAPHY AND BETTER COLONOSCOPIC PREPARATION Magnesium citrate–bisacodyl regimen proves better than castor oil for colonoscopic preparation CHUN-CHIA CHEN,WAI-WAH NG, FULL-YOUNG CHANG AND SHOU-DONG LEE Division of Gastroenterology,Veterans General Hospital-Taipei and National Yang-Ming University School of Medicine,Taipei,Taiwan Abstract Background: A clean colon preparation prior to endoscopy or X-ray examination is essential to obtain an accurate diagnosis. In order to determine which of two easily made preparations is better, this study compares colon cleansing efficacy, patient acceptance and side effects in patients given either a mag- nesium citrate–bisacodyl or a castor oil regimen prior to colonoscopy. Methods: Seventy outpatients scheduled for colonoscopy were randomized to receive one of two bowel evacuation regimens on the day prior to the examination. Group 1 (n = 36) received a magnesium citrate solution (250 mL) and bisacodyl (10 mg, orally). Group 2 (n = 34) received castor oil (60 mL, orally). Results: The cleansing effect of the magnesium citrate–bisacodyl regimen was significantly better than that of castor oil in the ascending colon and caecum (cleansing scores 5.2 ± 1.2 vs 3.5 ± 1.3, P < 0.0001), but similar to that of castor oil in the recto-sigmoid, descending and transverse colon. Abdominal pain (38 vs 11%, P < 0.01) and nausea (29 vs 8%, P < 0.05) were significantly more common in patients receiving the castor oil preparation than in patients administered with the magnesium citrate–bisacodyl regimen. More patients complained of poor acceptance with the castor oil regimen than with the mag- nesium citrate–bisacodyl regimen (24 vs 8%, P = 0.06). Conclusions: A combined oral magnesium citrate and bisacodyl regimen is effective and better than castor oil for colonoscopic preparation. © 1999 Blackwell Science Asia Pty Ltd Key words: bisacodyl, castor oil, colonoscopy, magnesium citrate. Correspondence: Dr F-Y Chang, Division of Gastroenterology,Veterans General Hospital-Taipei, No. 201, Sec. 2, Shih-Pai Road,Taipei 11217,Taiwan. Email: changfy@vghtpe.gov.tw. Accepted for publication: 5 July 1999.