Stability of nifedipine in an extemporaneously compounded oral solution

The stability of nifedipine in an extemporaneously compounded oral solution is described. A solution of nifedipine 10 mg/mL was prepared from commercially available nifedipine powder with polyethylene glycol 400, glycerin, and peppermint oil. Four samples were stored in amber glass bottles at room temperature under fluorescent lighting and analyzed in duplicate. Samples were analyzed immediately and at 7, 14, 23, and 35 days. Eight samples were stored in amber oral syringes and eight in amber oral syringes wrapped in aluminum foil; all were stored at room temperature under fluorescent lighting. Samples from foil-wrapped syringes were analyzed at 7 and 14 days; samples not wrapped in foil were analyzed after 7 days. Nifedipine concentrations were measured with a modified stability-indicating high-performance liquid chromatographic method. Excessive degradation was defined as a greater than 10% loss of initial drug concentration. There were no detectable changes in color or odor and no visible solids or microbial growth was observed in any sample. Samples in amber glass bottles and amber oral syringes wrapped in aluminum foil retained more than 90% of the initial nifedipine for 35 and 14 days, respectively. Samples packaged in amber oral syringes not wrapped in foil lost over 20% of the initial nifedipine concentration within 7 days. Nifedipine 10 mg/mL was stable in an oral solution prepared from commercially available powder in a peppermint-flavored vehicle for at least 35 days when stored at 22-25 degrees C in amber glass bottles and for at least 14 days when stored in amber oral syringes wrapped in aluminum foil.