American Journal of Health-System Pharmacy, Vol. 67, Issue 4, 287-289
Copyright © 2010 by American Society of Health-System Pharmacists

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Practice Report

Stability of extemporaneously prepared rifaximin oral suspensions

Mary Petrea Cober, Cary E. Johnson, Jordan Lee and Kenne Currie

MARY PETREA COBER, PHARM.D., BCNSP, is Clinical Assistant Professor—Pediatric Pharmacotherapy, Department of Clinical Sciences, College of Pharmacy, University of Michigan (UM), Ann Arbor, and Clinical Pharmacist—Pediatric Surgery, Department of Pharmacy, University of Michigan Hospitals and Health Centers (UMHHC), Ann Arbor. CARY E. JOHNSON, PHARM.D., FASHP, is Professor of Pharmacy, Department of Clinical Sciences, College of Pharmacy, UM, and Clinical Pharmacist—Pediatrics, Department of Pharmacy, UMHHC. JORDAN LEE, PHARM.D., is Pharmacist, CVS Pharmacy, Valencia, CA; at the time of writing he was a student, College of Pharmacy, UM. KENNE CURRIE, PHARM.D., is Executive Pharmacist, Target Pharmacy, Canton, MI; at the time of writing he was a student, College of Pharmacy, UM

Address correspondence to Dr. Cober at the Department of Pharmacy, University of Michigan Hospitals and Health Centers, 1500 East Medical Center Drive, SPC 5247, Mott F7786, Ann Arbor, MI 48105-5247 (mcober{at}umich.edu).

Purpose. 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 °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 A 1-mL sample was withdrawn from each of the six bottles with a micropipette immediately after preparation and at 7, 15, 30, and 60 days.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 µg/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. Conclusion. 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. Index terms: Antiinfective agents; Chromatography, liquid; Color; Compounding; Concentration; Hydrogen ion concentration; Rifaximin; Stability; Storage; Suspensions; Vehicles

 

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