Stability of phenylenphrine hydrochloride in nasal drops



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The stability of a 0.5 percent nasal solution of phenylephrine hydrochloride has been investigated. The stability tests were conducted at five different pH values (5,6,7,8, and 9) and at three different temperatures (22°, 40°, and 60° C.) for a period of 165 days. The nasal solutions contained methylparaben (0.02 percent) and propylparaben (0.01 percent) as the preservatives and sodium bisulfite (0.1 percent) as an antioxidant. The stability was checked using two different colorimetric methods, one for the hydroxyphenol moiety and the other for the secondary amino group on the side chain. All of the phenylephrine hydrochloride nasal solutions appeared to be stable (degradation less than 10 percent) even at higher temperatures and pH values, except that the decomposition of the secondary amino group was noted on three nasal solutions (pH 7, 8 and 9) which were stored at 40° C. This decomposition was due to the failure of the preservatives under the above mentioned conditions, as indicated by the growth of the fungus, which was identified as an Aspergillus species. The rate of decomposition appeared to be mixed. All other solutions discolored, except two which were buffered at pH 5 and 6 and stored at room temperature. In conclusion, it may be stated that phenylephrine hydrochloride nasal solutions cannot be buffered at a pH above 6 and cannot be stored above room temperature.