Carnauba wax as a promising excipient in melt granulation targeting the preparation of mini-tablets for sustained release of highly soluble drugs

•Carnauba wax was exploited as a novel excipient for melt granulation.•Melt granulation improved tabletability and flowability of both captopril and metformin HCl.•Sustained release of captopril was achieved by Ethocel™ at a 50% (w/w) concentration.•Sustained release of metformin HCl was reached by film-coating (Kollicoat® SR 30D: Opadray® II).•Carnauba wax assisted sustaining the drug release in conjunction with the polymers.

Mini-tablets are a new tendency in solid dosage form design for overcoming therapeutic obstacles such as impaired swallowing and polypharmacy therapy. Among their advantages, these systems offer therapeutic benefits such as dose flexibility and combined drug release patterns. The use of lipids in the formulation has also drawn considerable interest as means to modify the drug release from the dosage form. Therefore, this paper aimed at developing sustained release mini-tablets containing the highly soluble drugs captopril and metformin hydrochloride. Carnauba wax was used as a lipid component in melt granulation, targeting the improvement of the drugs poor flowability and tabletability, as well as to sustain the drug release profiles in association with other excipients. To assist sustaining the drug release, Ethocel™ (EC) and Kollicoat® SR 30D associated with Opadry® II were employed as matrix-forming and reservoir-forming materials, respectively. The neat drugs, granules and the bulk formulations were evaluated for their angle of repose, compressibility index, Hausner ratio and tabletability. Mini-tablets were evaluated for their weight variation, hardness, friability, drug content and in-vitro drug release. The results indicated that melt granulation with carnauba wax improved the flow and the tabletability of the drugs, allowing the preparation of mini-tablets with adequate tensile strength under reduced compaction pressures. All mini-tablet formulations showed acceptable hardness (within the range of 1.16 to 3.93 Kp) and friability (< 0.1%). The melt-granulated captopril in matrix systems containing 50% EC (45P, 100P or 100FP) and the melt-granulated metformin hydrochloride in reservoir systems coated with Kollicoat® SR 30D and Opadry® II (80:20 with 10% weight gain or 70:30 with 20% weight gain) exhibited release profiles adequate to sustained release formulations, for over 450 min. Therefore, carnauba wax proved to be a promising excipient in melt granulation targeting the preparation of mini-tablets for sustained release of soluble drugs.

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