Assessing Hibiscus rosa-sinensis Linn as an Excipient in Sustained-Release Tablets - Pharmaceutical Technology

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Assessing Hibiscus rosa-sinensis Linn as an Excipient in Sustained-Release Tablets
Natural gums and mucilage are biocompatible, cheap, readily available, and represent a potential source of excipients. The authors examine the functionality of mucilage extracted from the leaves of Hibiscus rosa-sinensis Linn as an excipient in a sustained-release tablet formulation.

Pharmaceutical Technology
Volume 32, Issue 1

Table III: Formulation of tablets and Y60, Y300, and t80 of preliminary batches.
The flow properties and compressibility of the dried mucilage, including bulk and tapped density, Carr's index, Hausner ratio, and the angle of repose were assessed and compared with those of guar gum and ispaghula husk (see Table II). The angle of repose of a powder provides an insight into the magnitude of the cohesiveness of the powder and hence, its flowability. Mildly cohesive powders have angles of repose between 40° and 60° when measured by standard methods. Dried mucilage has an angle of repose of 27.83°. Guar gum and ispaghula husk have an angle of repose of 42.27°and 38.79°, respectively. From these results, the authors infer that the dried mucilage powder was less cohesive and had superior flow property. The Hausner ratio previews the degree of densification that could occur during tableting: the higher the ratio, the greater the propensity of the powder to densify. This phenomenon may produce tablets that lack uniformity of weight and content. The dried mucilage has excellent flow properties compared with those of guar gum and ispaghula husk. Dried mucilage, therefore, has flow properties suitable for use in a direct-compression formulation.

Table IV: Formulation and dissolution characteristics of batches in a 32 full factorial design.
The average crushing strength of the prepared tablets was 4.8 kg/cm2 , a value which shows good strength. The friability was < 1% (i.e., between 0.75 and 0.91%). Tablets prepared from dried-powdered mucilage that passed the standard for uniformity in weight indicate homogenous drug content. These results show that tablets prepared from dried-powdered mucilage can be used as a directly compressible vehicle because of good hardness, low friability, and tablet-weight uniformity.

Table III shows the composition of the preliminary batches (L1 to L3) and the results of their dissolution studies. Table IV shows the composition of the nine batches of the factorial design and the results of their dissolution studies. When the dissolution study of the preliminary batches was performed, the complete drug release was obtained within 9, 10, and 11 h with different proportions of mucilage and 100 mg of diclofenac sodium (see Table III). The authors concluded that mucilage is suitable as a sustained-release matrixing agent for a diclofenac sodium tablet. Four criteria were established for the desired drug-release profile:

  • A release of 20–25% of the drug within the first hour.
  • Drug release after 5 h was 40% < Y300 < 60%
  • Prolonged drug release of the remaining drug followed during 12 h, preferably at a relatively constant rate
  • The time to release 80% of the drug was 490 < t80 < 590 min.


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