Loperamide delays absorption of theophylline from a sustained-release preparation
Clinical evidence,mechanism, importance and management
A study of effects of altering transit time of drugs through small intestine found that when 12 healthy subjects were given high-dose loperamide (8 mg every 6 hrs for a total of 8 doses), rate, but not extent, of absorption of a single 600mg dose of sustained-release theophylline (Theo-24) was decreased. The maximum serum theophylline levels were reduced from 4.6 to 3.2 micrograms/mL,and this peak level occurred at 20 hrs instead of 11 hours. One suggested reason for these effects is that loperamide inhibits movement of gut, thereby decreasing dissolution rate of Theo-24 pellets (See reference number 1). More study is needed to establish clinical significance of interaction in patients receiving long-term theophylline.
1. Bryson JC,Dukes GE, Kirby MG, Heizer WD, Powell JR. Effect of altering small bowel transittime on sustained release theophylline absorption. J Clin Pharmacol (1989) 29, 733–8.