Effect of magnesium stearate or calcium stearate as additives on dissolution profiles of diltiazem hydrochloride from press-coated tablets with hydroxypropylmethylcellulose acetate succinate in the outer shell

Effect of magnesium stearate (MgSt) or calcium stearate (CaSt) on the disso lution profiles of diltiazem hydrochloride in the core of press-coated (PC) tablets with an outer shell composed of hydroxypropylmethylcellulose aceta te succinate (HPMCAS) was evaluated by porosity and changes in IR spectra o f tablets. In JP first fluid (pH 1.2), the lag time increased with decreasi ng porosity and was greatest by the: addition of MgSt to HPMCAS. While, in JP second fluid (pH 6.8), it increased with decreasing porosity by the addi tion of CaSt, but hardly changed by the addition of MgSt. Thus. using table ts prepared with the same composition as the outer shell, the changes in IR spectra and uptake amount of the dissolution media after immersion in firs t fluid and second fluid were determined. The results suggested that some p hysicochemical interaction occur between MgSt and HPMCAS in tablets with HP MCAS and MgSt and the uptake increased markedly in each dissolution medium, These phenomena seem to cause a prolongation of lag time in first fluid bu t a shortening of it in second fluid in PC tablets with HPMCAS and MgSt. In contrast, CaSt and HPMCAS did not show such interactions and increased the hydrophobic properties of the outer shell. Consequently, the lag time was only slightly prolonged in first fluid, however, markedly prolonged in seco nd fluid due to suppression of second fluid penetration into micro pores in the outer shell and HPMCAS gel formation on the surface in PC tablets with HPMCAS and CaSt. (C) 2001 Elsevier Science B.V. All rights reserved.