A 32 full factorial design was constructed to study the effect of dried mucilage powder (X1) and amount of lactose (X2) on the drug release of the diclofenac sodium tablets. The dependent variables chosen were Y60,Y300, and t80 (i.e., the percentage of drug released in 60 and 300 min, respectively and the time to release 80% of the drug). The following
statistical model incorporating interactive and polynomial terms was used to evaluate the response:
in which Y is the dependent variable, b0 is the arithmetic mean response of the nine runs, and bi is the estimated coefficient for the factor Xi. The main effects (X1 and X2) represent the average result of changing one factor at a time from its low to high value. The interaction terms (X1X2) show how the response changes when two factors are simultaneously changed.
The Y60, Y300 and t80 values for the nine batches (HL1 to HL9) showed a wide variation: 22.38 to 34.00%, 52.75 to 69.33%, and 388 to 547 min, respectively.
The data (see Table IV) clearly indicate that the values are strongly dependent on the selected variables. The fitted equation
relating the response Y60, Y300, and t80 to the transformed factor is shown in equations 6–8:
The values of the correlation coefficient were 0.9879, 0.9831, and 0.9870, respectively, indicating a good fit. Equations
6 and 7 may be used to obtain a reasonable estimate of the response because a small error of variance was noticed in the replicates.
The polynomial equation can be used to draw conclusions after considering the magnitude of the coefficient and the mathematical
sign it carries (i.e., positive or negative). The data demonstrate that both factors (X1 and X2) affect the drug release Y60, Y300, and t80. The low value X1X2 of the coefficient also suggests that the interaction between X1 and X2 is not significant.
Batches HL3 and HL6 met the set criteria of Y60, (i.e., 20% < Y60, < 25%. Batches HL3, HL5, HL6, and HL9 met the set criteria of Y300 (i.e., 40% < Y300 < 60%. Batches HL6 and HL9 met the set criteria of t80 between 490 and 590 min. Among the entire batches, only HL6 fulfilled all the selection criteria, which included prolonged
drug release of the remaining drug over 12 h. Batch HL6, therefore, was selected as the optimized batch.