Visicol® Tablets, taken in two doses of 30 grams approximately twelve hours apart, induce a diarrhea, which rapidly and effectively cleanses the entire colon. Each administration has a purgative effect for approximately 1 to 3 hours. The primary mode of action is thought to be through osmotic action of sodium, causing large amounts of water to be drawn into the bowel, promoting bowel evacuation.

Twenty-three normal healthy volunteer subjects participated in an open-label pharmacokinetic study of Visicol® Tablets designed to generate concentration-time curves for serum inorganic phosphorus levels after administration of Visicol® Tablets. Subjects were administered Visicol® Tablets consistently with the prescribed labeling for colon cleansing. A 30 gram dose (20 tablets given as 3 tablets every 15 minutes with clear liquids) was given beginning at 6 PM in the evening. The 30 gram dose (20 tablets given as 3 tablets every 15 minutes with clear liquids) was repeated the following morning beginning at 6 AM. The serum phosphorus level rose to a maximum mean (± standard deviation) peak of 3.7 ± 1.63 mg/dL above baseline, at a median of 3 hours after the first administration of Visicol® Tablets. Following the second administration of Visicol® Tablets the serum phosphorus level rose to a maximum mean (± standard deviation) peak of 4.4 ± 1.86 mg/dL above baseline, at a median of 4 hours.

Figure 1. Mean (±standard deviation) serum phosphorus concentrations

Solid bars ( ____ ) represent the lower (2.6 mg/dL) and upper (4.5 mg/dL) limits of the reference range for the clinical laboratory.

The serum phosphorus level remained above baseline for a median of 24 hours after the initial dose of Visicol® Tablets (range 16 to 48 hours), with a maximum mean decrease at 18 hours in serum calcium of 0.3 mg/dL ± 0.3 mg/dL.

Renal insufficiency: The effect of renal dysfunction on Visicol® Tablets pharmacokinetics has not been studied. Since the ionized, inorganic form of phosphate in the circulating plasma is excreted almost entirely by the kidneys, patients with renal disease may have difficulty excreting a large phosphate load. Thus, Visicol® Tablets should be used with caution in patients with impaired renal function.

Hepatic insufficiency: Visicol® Tablets have not been investigated in patients with hepatic failure. The ionized, inorganic form of phosphate in the circulating plasma is excreted almost entirely by the kidneys. Visicol® is not expected to be metabolized in the liver.

Geriatric: Both AUC and Cmax values of serum phosphate were less than half in subjects >70 years of age compared to subjects <70 years of age, based on the results of a single pharmacokinetic study, which included 6 elderly volunteers. Plasma half-life increased two-fold in subjects >70 years of age compared to subjects <50 years of age (3 subjects and 5 subjects, respectively).

Gender: No difference in serum phosphate AUC values were observed in the single pharmacokinetic study conducted in 13 male and 10 female healthy volunteers.

A total of 957 adult patients were enrolled and treated in the controlled clinical trials of Visicol® Tablets. Males and females were about equally represented. Approximately 87% of the study population was Caucasian. Visicol® Tablets were found to be comparable in cleansing efficacy to the comparison drug, a commercially available polyethylene glycol-salt (PEG-salt solution) solution (Cherry Flavor NuLYTELY). Two identical, single (investigator) blind, randomized, multicenter trials were conducted comparing the efficacy and safety of Visicol® Tablets and the PEG-salt solution comparator as a colon cleansing agent in patients undergoing routine diagnostic colonoscopy. In each study, over 200 patients were randomized to self-administer the Visicol® Tablets and over 200 were randomized to self-administer the PEG-salt solution comparator. Colonoscopy was generally performed within 5 hours of the second dose. Physicians used a four-point, validated Physician Questionnaire to assess efficacy. The distribution of "excellent", "good", "fair" and "inadequate", as evaluated by the physician performing the colonoscopy, was comparable in both groups. Cleansing efficacy observed in these studies is described in the following table.

Brand Name: Visicol
Generic Name: Sodium Phosphate Monobasic Monohydrate, Sodium Phosphate Dibasic Anhydrous

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