To evaluate the potential differences in the adverse event (safety) profile between 4 mg of prucalopride daily for 4 weeks; titration up to a 4-mg total daily dose of prucalopride by starting at 1 mg for 2 days, 2 mg for 2 days, to 4 mg thereafter; and placebo given as oral tablets once daily for 4 weeks in patients with chronic constipation