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

Preparation of diclofenac sodium tablets. The required quantities of diclofenac sodium and dried mucilage powder (sieve number 80) were physically admixed. Lactose was included in the nine batches of factorial design. The powder blend was lubricated with 1% w/w talc and 2% w/w magnesium stearate. Lubrication was performed in a glass jar for 2 min. Each tablet contained 100 mg of the drug. The tablets were prepared by direct compression on a rotary tablet press (Rimek II, Karnavati Engineering, Ahmedabad, India) and fitted with concave punches of 9 mm in diameter. The turret was rotated at a fixed speed of 30 rpm (34).

Hardness and friability test. Hardness was determined by using the Monsanto hardness tester, and friability was evaluated as the percentage weight loss of 20 tablets tumbled in a friabilator (Model EF2, Electrolab, Mumbai, India) for 4 min at 25 rpm. The tablets were dedusted, and the loss in weight caused by the fracture or abrasion was recorded as the percentage friability.

Uniformity of weight. The weight-variation test was performed. Twenty tablets were weighed individually, and the average weight was calculated.

Dissolution-rate study. The drug-release study was carried out using an USP XXIII paddle apparatus at 37 0.50 C at 50 rpm using 900 mL of distilled water and phosphate buffer (pH 6.8) as the dissolution medium (n = 5). A 5-mL sample solution was withdrawn at predetermined time intervals, filtered through a 0.45-μm membrane filter, diluted suitably, and analyzed spectrophotometrically at 276 nm using a UV-visible double-beam spectrophotometer (Shimazdu-UV 1700, Shimazdu, Kyoto, Japan). Equal amounts of fresh dissolution medium were replaced immediately after withdrawing a test sample. The percentage of drug that dissolved at different time intervals was calculated using a regression equation generated from the standard curve. Drug release from the optimized batch (HL6) and a market preparation of the drug were studied in distilled water.

Full factorial design. A 32 randomized full factorial design was used. Two factors were evaluated, each at three levels, and experimental trials were performed at nine possible combinations. The ratio of mucilage (X 1) and amount of lactose (X2) were selected as independent variables. The time required for 80% drug dissolution (t80) and percentage drug released in 60 min (Y60) and 300 min (Y300) were selected as dependent variables.

Hydration capacities and erosion studies. Erosion and water uptake of the formulated tablets were determined under conditions identical to those previously described for dissolution testing. Water uptake and mass loss were determined gravimetrically according to the following equations (35):

Percent water uptake =

Three tablets were used per time point. At predetermined times, the ring-mesh assemblies supporting the partially hydrated tablets were carefully removed, and the tablets were lightly blotted with tissue paper to remove excess surface water. After determining the wet weight, the tablets were dried at 70 C for one day before reweighing to determine the remaining dry weight. The test was performed at speeds of 50 and 100 rpm. Placebo tablets consisting of pure mucilage were tested in the same way. All studies were performed in triplicate.


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