Pharmacology Update

Sodium Picosulfate, Magnesium Oxide, and Citric Acid (Prepopik™)

By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD, Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; and Assistant Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Elliott and Chan report no financial relationships relevant to this field of study.

A colonic cleansing preparation has been approved by the FDA. The preparation contains sodium picosulfate, magnesium oxide, and citric acid and forms sodium picosulfate and magnesium citrate upon reconstitution (PSMC). The preparation has been available outside the United States since 1980 and is manufactured and marketed by Ferring Pharmaceuticals as Prepopik.


PSMC is indicated for cleansing of the colon prior to colonoscopy in adults.1 The preparation is supplied as two packets, each containing 10 mg of sodium picosulfate, 3.5 g of magnesium oxide, and 12 g of anhydrous citric acid.


The recommended dose is the split-dose regimen: The first dose is taken between 5-9 p.m. (followed by five 8-ounce glasses of clear liquid) the evening before the procedure, and the second dose is taken the next day about 5 hours before the procedure (followed by three 8-ounce glasses of clear liquid).

An alternative dosing is the day-before regimen, with the first dose in the early evening (4-6 p.m.) before the procedure, followed by five 8-ounce glasses of clear liquid, and the second dose in the late evening (10 p.m.-12 a.m.), followed by three 8-ounce glasses of clear liquid. All liquids should be consumed within 5 hours.

Potential Advantages

The total volume of the active ingredients is 10 ounces compared to 2 liters for polyethylene glycol electrolyte solution (PEG). However, the total liquid consumed is about the same. Better patient acceptance for PSMC has been reported compared to the PEG solution.2

Potential Disadvantages

The action of sodium picosulfate results in electrolyte and water retention in the colon, increasing the risk of serious fluid and electrolyte abnormalities.1,2 This is unlikely with the nonabsorbable isotonic PEG preparation.2 Use with caution in patients with diminished renal function.1


Sodium picosulfate is the prodrug for 4,4-dihydroxydiphenyl-(2-pyridyl) methane, which acts as a colonic stimulant while magnesium citrate acts as an osmotic laxative. The non-inferiority of this combination was shown for the two dosing regimens compared to PEG alone with two 5 mg bisacodyl tablets taken on the day prior to the procedure.1 The split-dose study randomized 601 subjects and the day-before dosing randomized 594 subjects. The primary endpoint was the proportion of subjects with successful colon cleansing as determined by blinded colonoscopists using the Aronchick Scale. The proportion of subjects with successful cleansing was 84.2% for PSMC compared to 74.4% for PEG. For the day-before dosing, the success rate was 83.0% and 79.7%, respectively. In a comparative study (n = 236), the split dose has been reported to provide better cleansing than the alternate dose.3 The wholesale acquisition cost for Prepopik is $74.95 compared to $19.17 for Golytely, and $13.72 for a generic preparation.

Clinical Implications

PSMC provides an alternative to PEG for colon cleansing. The volume of “salty” solution consumed is significantly less than PEG but there is a greater risk of serious fluid and electrolyte abnormality.


1. Prepopik Prescribing Information. Parsippany, NJ: Ferring Pharmaceuticals; July 2012.

2. Hoy SM, et al. Sodium picosulfate/magnesium citrate: a review of its use as a colorectal cleanser. Drugs 2009;69: 123-136.

3. Flemming JA, et al. Split-dose picosulfate, magnesium oxide, and citric acid solution markedly enhances colon cleansing before colonoscopy: A randomized, controlled trial. Gastrointest Endos 2012;75:537-544.