Stability of extemporaneously prepared rifaximin oral suspensions.
OBJECTIVE
The stability of extemporaneously prepared rifaximin oral suspensions was studied.


METHODS
An oral suspension of rifaximin 20 mg/mL was prepared by thoroughly grinding six 200-mg tablets of rifaximin in a glass mortar. Thirty milliliters of Ora-Plus and 30 mL of either Ora-Sweet or Ora-Sweet SF were mixed and added to the powder to make a final volume of 60 mL. Three identical samples of each formulation were prepared and placed in 2-oz amber plastic bottles with child-resistant caps and were stored at room temperature (23-25 degrees C). A 1-mL sample was withdrawn from each of the six bottles with a micropipette immediately after preparation and at 7, 15, 30, and 60 days. After further dilution to an expected concentration of 20 microg/mL with mobile phase, the samples were assayed in duplicate using stability-indicating high-performance liquid chromatography. The samples were visually examined for any color change and pH was tested on each day of analysis. Stability was determined by evaluating the percentage of the initial concentration remaining at each time point and defined as retention of at least 90% of the initial concentration of rifaximin.


RESULTS
At least 99% of the initial rifaximin remained throughout the 60-day study period in both preparations. There were no detectable changes in color, odor, taste, or pH and no visible microbial growth in any sample.


CONCLUSIONS
Extemporaneously prepared suspensions of rifaximin 20 mg/mL in 1:1 mixtures of Ora-Plus with either Ora-Sweet or Ora-Sweet SF were stable for at least 60 days when stored in 2-oz amber plastic bottles at room temperature.
Cober
Mary Petrea
MP
Department of Clinical Sciences, College of Pharmacy, University of Michigan Hospitals and Health Centers, 1500 East Medical Center Drive, Ann Arbor, MI 48105-5247, USA. mcober@umich.edu
Johnson
Cary E
CE
Lee
Jordan
J
Currie
Kenne
K
D000284:Administration, Oral; D000890:Anti-Infective Agents / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004339:Drug Compounding / Q000379:methods; D004355:Drug Stability; D004356:Drug Storage / Q000379:methods; D014677:Pharmaceutical Vehicles / Q000737:chemistry; D012294:Rifamycins / Q000008:administration & dosage / Q000737:chemistry*; D000078262:Rifaximin; D013535:Suspensions / Q000737:chemistry
D000890:Anti-Infective Agents; D014677:Pharmaceutical Vehicles; D012294:Rifamycins; D013535:Suspensions; D000078262:Rifaximin