Effect of theophylline on gastroesophageal reflux in normal adults.

In a randomized, double-blind manner, 15 normal adults were given a single oral loading dose of anhydrous theophylline (6.5 +/- 0.9 mg/kg) and nine normal adults were given placebo. All subjects were tested for serum theophylline levels, acid reflux (using intraesophageal pH probe), and lower esophageal sphincter pressure (LESP) at 1.5, 4, and 8 hr after treatment. Of subjects with negative baseline acid reflux tests, eight of 13 (61.5%) given theophylline developed positive acid reflux tests compared with none of eight subjects given placebo. One of nine (11%) placebo subjects reported heartburn compared with 11 of 15 (73%) subjects given theophylline. The maximum mean percent change in LESP from baseline was +5.62 +/- 28.8% in the placebo group and -25.01 +/- 23.7% in the theophylline group (p = 0.01) at 4 hr after treatment. While only two of nine (22%) adults given placebo had at least a 14% reduction in LESP following treatment, all of the 15 subjects sustained a minimum of 14% relaxation in LESP. This study confirms that oral theophylline at therapeutic serum levels inhibits LESP and induces gastroesophageal reflux (GER) measured by acid reflux tests in most normal adults.