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Laboratory and Animal Investigations |

Stability of Frozen Methacholine Solutions in Unit-Dose Syringes for Bronchoprovocation*

Michael J. Asmus, PharmD; Leigh M. Vaughan, PharmD; Malcolm R. Hill, PharmD; Sarah E. Chesrown, MD, PhD; Leslie Hendeles, PharmD
Author and Funding Information

*From the Department of Pharmacy Practice (Dr. Asmus) and Pediatric Pulmonary Division (Drs. Chesrown and Hendeles), College of Medicine, University of Florida, Gainesville, FL; and Dura Pharmaceuticals (Drs. Vaughan and Hill), San Diego, CA.

Correspondence to: Michael J. Asmus, PharmD, University of Florida, Health Sciences Center, Box 100486, Gainesville, FL 32610-0486; e-mail: asmus@cop.ufl.edu



Chest. 2002;121(5):1634-1637. doi:10.1378/chest.121.5.1634
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Objective: Methacholine solutions < 0.25 mg/mL must be prepared fresh daily, while concentrations ≥ 0.25 mg/mL must be prepared at 2-week intervals according to US Food and Drug Administration-required labeling. The purpose of this report was to determine whether freezing methacholine solutions in unit-dose syringes would allow less frequent preparation.

Design: Diluent containing 0.5% sodium chloride, 0.275% sodium bicarbonate, and 0.4% phenol was used to prepare 11 concentrations of methacholine ranging from 0.031 to 32.0 mg/mL. Three milliliters of each dilution was placed into 5-mL polypropylene syringes and immediately frozen. Methacholine concentrations were determined using a validated high-performance liquid chromatography assay after preparation (time zero) and at 0.5, 1, 1.5, 2, 3, 4, 5, and 6 months. On the day of analysis, the samples were allowed to thaw to room temperature. An additional set of each dilution was stored at room temperature for 24 h after thawing and then analyzed for methacholine.

Results: Samples ≥ 0.062 mg/mL analyzed immediately after thawing retained ≥ 90% of labeled potency for at least 6 months, while the 0.031-mg/mL sample retained 90% potency for 4 months. Most samples analyzed 24 h after thawing lost potency.

Conclusion: If prepared and stored in unit-dose syringes frozen, methacholine solutions containing 0.062 to 32.0 mg/mL can be prepared at 6-month intervals, and solutions containing 0.031 mg/mL can be prepared at 4-month intervals. Once thawed, unused methacholine solutions should be discarded.

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