To improve oral absorption and patient compliance when using amlodipine, novel coated dextrin microcapsules incorporable into orally disintegrating tablets (ODT's) were investigated. Amlodipine-loaded dextrin microcapsules (ADM) were prepared by spray-drying a mixture of amlodipine free base dissolved in ethanol and aqueous dextrin solution. The ADM were suspended in Eudragit(®) EPO solution in ethanol and subsequently spray-dried to collect coated ADM (CADM). The ADM or CADM were blended with ODT excipients and then directly compressed into ODTs. The ADM and CADM used were both spherical with smooth surfaces and had mean particle sizes of 13.3 and 18.5μm, respectively. Amlodipine was dispersed in an amorphous state and was readily encapsulated within ADM or CADM. Unlike the ADM, the tableted CADM remained intact without rupture during tableting, which was consistent with no loss of ethanol (0.82%) entrapped in the ODTs containing the CADM (ODTs-CADM). The amlodipine content appeared to be uniformly maintained as designed in all the dextrin microcapsules and ODTs. The ODTs-CADM compressed with 3kp of hardness showed acceptable ODT characteristics: fast disintegration time (29.8s) and low friability (0.1%). Drug dissolution from the ODTs-CADM was much faster than that of amlodipine free base itself at both pH 1.2 and 6.8 over the tested time. CADM demonstrated significantly higher plasma concentrations (2.7 fold in AUC0-24h and 2.5 fold in Cmax) in SD rats than did amlodipine free base. These results indicate that CADM substantially increased the oral absorption of amlodipine and can be incorporated into ODTs while maintaining their original physicochemical features. The dextrin microcapsules coated using Eudragit(®) EPO may be applied to the development of an amlodipine ODT formulation for improving geriatric patient compliance.
Keywords: Amlodipine free base; Coated dextrin microcapsules; Oral absorption; Orally disintegrating tablets; Spray drying.
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