Q I work as a relief pharmacist for a chain drugstore. Thepharmacists at 2 stores in the chain compound topical formulationsthat contain nystatin powder and other ingredients, indifferent proportions. At one store, the formulation is refrigerated;at the other it is not. Nystatin powder is a refrigerated product.Should both preparations be refrigerated and so labeled oncecompounded?
A Nystatin USP is sometimes referred to as Nystatin forExtemporaneous Compounding of Oral Suspension andhas a specified potency of 5000 units per mg when used in thisfashion. It is distinguished from Nystatin for Oral Suspension,which may contain flavoring, preservatives, and the like; and fromNystatin Topical Powder, which contains nystatin diluted with inertmaterial for use in the treatment of dermatologic conditions.
Nystatin degrades rapidly in the presence of moisture; hencethe admonition to dispense it as dry powder with "Refrigerate"labeling. (Refrigeration slows degradation; humidity in a refrigeratorgenerally is lower than ambient humidity.) The patient "compounds"the nystatin in water at the time of administration. Thematerial degrades to subpotency within ~90 days after the containeris opened. The material reportedly is stable at room temperature(sealed) for ~30 days. When combined with other ingredientsin dry form (Nystatin Topical Powder) or in aqueoussuspension with sugar, the product is stable. Moreover, in an oilin-water emulsion (Nystatin Cream USP) or in an anhydrousbase (Nystatin Ointment USP), the nystatin reportedly is stablefor an extended period. The USP Compounding Monograph<795> discusses stability of compounded products where nostudies are available and no adequate information on which tomake professional judgment can be found. When water is present,the product is assigned a 14-day "beyond-use" date. If theproduct is anhydrous, the beyond-use date is 30 days. One factoraffecting stability, beyond those discussed, is interaction ofingredients in a compounded preparation. The possibility ofincompatibilities should be considered when assigning abeyond-use date and specifying storage conditions.
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Mr. Erickson is director of professional affairs at Gallipot Inc.