Long term stability of polyethylene glycol 3350 and lactulose in common liquids

Introduction: Constipation is a common problem in pediatric patients.  Polyethylene glycol (PEG 3350) and lactulose are commonly used to treat children with constipation, but adherence rates have been reported as <40%.  To increase adherence, PEG 3350 or lactulose can be mixed with liquids a child may be more likely to drink.  However, there is no stability information for PEG 3350 or lactulose in liquids other than water.

Objectives: Can lactulose (Kristalose®) and PEG 3350 (Miralax®) be mixed with water, juices, soda, and milk and maintain stability for up to 72 hours?

Study Design: In vitro stability testing

Methods: Commercially available lactulose and PEG 3350 were prepared with water according to their respective package insert directions, as well as prepared with 4 common liquids:  soda, orange juice, apple juice, and milk.  Physical characteristics of the solutions were evaluated at time of preparation (time 0) and at 24 hour intervals for 3 days.  At each time point, the samples were examined for obvious changes in color and odor.  Immediately after the visual/odor observations, the samples were analyzed using Matrix Assisted Laser Desorption Ionization (MALDI) mass spectrometry.  Stability of PEG 3350 was assessed by monitoring for its sustained presence as well as formation of degradation products.  Since there are no known degradants of lactulose, stability was assessed by monitoring only for its sustained presence.

Results: There were no significant differences in the profiles for 0hr and 72hr, suggesting the stability of both PEG 3350 and lactulose.

Conclusions: Both PEG 3350 (Miralax®) and lactulose (Kristalose®) were stable for 72 hours in water, juice, soda, and milk.  This stability finding has significant impact on clinical practice as these common liquids may be more preferable to children, thus potentially increasing adherence.