Action of in situ nitroglycerin on upper anal canal pressure of patients with terminal constipation. A pilot study.

Nitroglycerin (NTG) in situ reduces the pressure of the upper anal sphincter (UAS). We have tested the effects of NTG on the UAS of patients with terminal constipation. We studied two groups of constipated patients. Group 1 consisted of 11 patients (nine females and two males) with hypertonicity of the UAS (> 70 mm Hg); age was 49.5 +/- 15.6 years. Group 2 consisted of 10 patients (nine females and one male) without hypertonicity; age was 40.1 +/- 14.1 years. Group 3 consisted of eight asymptomatic controls (four females and four males); age was 51.7 +/- 6.9 years. After a 10-minute resting pressure recording of the UAS with a water-filled balloon, the probe was pulled through the outside and the UAS was assessed after spreading 5 mg of placebo and then 5 mg of NTG on the balloon. Resting pressure (RP), delay of the pressure decrease (DP), pressure after five minutes either during the NTG (PN5) or placebo (PP5) period, and mean duration of the pressure decrease (MD) were measured. None of the subjects experienced a decrease of PP5 vs. RP. All patients in Group 1 (106.2 vs. 38.4 mm Hg), Group 2 (57.9 vs. 31.4 mm Hg), and controls (62.2 vs. 33.7 mm Hg) experienced a significant decrease of pressure of the UAS (P < 0.005). Delay of the pressure decrease was less than two minutes, with wide interindividual variability of duration of the pressure decrease. Mild side effects--anal pain and transient headache--were reported in five patients. In situ NTG significantly reduced UAS Pressure in all groups. NTG has to be evaluated in anal pathology, especially in patients with hypertonic sphincter terminal constipation or acute hypertonicity of the sphincter due to a fissure.