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  • Author or Editor: T. Kőszegi x
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A reversed-phase ion-pairing liquid chromatographic (RP-IP-HPLC) method for simultaneous assay of theophylline (TH), phenobarbital (PB), codeine (CD), and ephedrine (EP) in an extemporaneous (magistral) suppository was developed and validated and used to investigate a reported serious adverse event. Samples were dissolved in dichloromethane and extracted by two-step liquid-liquid extraction with acetate buffer (pH 5.0) and, subsequently, 0.1 m NaOH solution. Separation was performed on an end-capped C18 silica column with stepwise gradient elution. Sample preparation and chromatographic conditions were optimized on the basis of the pK a values of the analytes. Freedom from interference from the excipients, linearity (r 2 > 0.999 for all the active ingredients), range (0.01–0.08 mg mL−1 for TH, CD, and EP; 0.0025–0.02 mg mL−1 for PB), intra-day and inter-day precision, and accuracy (recovery >95% for TH, CD, and EP and >90% for PB) of the method were demonstrated. Non-compliance of the examined product was confirmed.

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