Evaluation of nifedipine preparations by chromatographic-spectrophotometric methods.
The content of nifedipine in 10 currently available preparations (tablets, capsules, dragees and drops) was analyzed. In the qualitative analysis, a TLC method was employed, whereas in the quantitative analysis, a chromatographic-spectrophotometric method developed in our laboratory (TLC-UV), a TLC-UV method according to USP XXI, and the method of gas chromatography coupled with mass spectrometry (GC-MS) were employed. For all the preparations under study, the presence of at least one decomposition product as well as a decrease in the content of active component, in most cases proportional to the storage time, were observed. However, in none of the preparations pyridine nitro derivative decomposition products were found, but in each the presence of nitroso derivative was reported. As a result, it was stated that about a half of the preparations studied do not meet the requirements of USP XXI as for as the content of the active substance is concerned, which suggests that the expiration date is shorter by 6 to 12 months.