Purpose: To develop an optimised press-coated tablets of losartan potassium using an admixture of a hydrophilic polymer, hydroxypropylmethylcellulose (HPMC) and microcrystalline cellulose (MCC) in order to achieve a predetermined lag time for chronotherapy.
Methods: The press-coated tablets (PCT) containing losartan potassium in the inner core were prepared by compression-coating with HPMC 100KM alone and admixed with MCC as the outer layer in different ratios. The effect of the outer layer on the lag time of drug release was investigated. The parameters determined were tablet tensile strength, friability, drug content and in vitro dissolution. The optimised formulation was further characterized with Fourier-transform infrared spectroscopy (FTIR) and powder X-ray diffractometry (PXRD) to investigate any drug/excipient modifications/interactions.
Results: The tensile strength values of all the PCT were between 1.12 and 1.23MNm-2 and friability was < 0.36 %. The release profile of the press-coated tablet exhibited a distinct lag time before burst release of losartan potassium. Lag time was dependent on the ratio of HPMC/MCC in the outer shell. The lag time was from 0.5 to 18.5 h and could be modulated as it decreased as the amount of MCC in the outer layer increased. There was no modification or chemical interaction between the drug and the excipient.
Conclusion: Formulation LPP2, with HPMC/MCC of (30:70) in the outer shell and showing a predetermined lag time of 6 h prior to burst release of the drug from the press-coated tablet was taken as the optimized formulation.