Table 2.
Mathematical models fitted to the experimental ROP release curve: calculated fitting parameters, the square of correlation coefficient (R2), and chi-square (χ2). Data were fitted until the plateau is reached (64 min—96.4% of drug released), except in the Peppas–Salhin *** case (60% of ROP released).
| Equation Number | Fitting Equations | Calculated Parameter(s) | R2 | χ2 |
|---|---|---|---|---|
| (1) |
Zero Order
D = k·t |
k: 1.533 ± 0.035 | 0.962 | 29.989 |
| (2) |
First Order
D = 100·(1 − e−k t) |
k: −0.024 ± 0.002 | 0.865 | 145.406 |
| (3) |
Higuchi
D = k·t0.5 |
k: 9.832 ± 0.497 | 0.758 | 260.997 |
| (4) |
Hopfenberg *
D = 100·[1 − (1 − k·t)n] |
k: 0.016 ± 2.4·10−4 | 0.976 | 25.419 |
| (5) |
Korsmeyer-Peppas
(Power Law) D = k·tn |
k: 0.782 ± 0.112 n: 1.177 ± 0.037 |
0.987 | 13.598 |
| (6) |
Peppas-Salhin **
D = k1·tm + k2·t2m |
k1: −10.912 ± 2.897 k2: 5.571 ± 1.472 m: 0.404 ± 0.025 |
0.994 | 6.396 |
| (6) |
Peppas-Salhin ***
D = k1·tm + k2·t2m |
k1: −10.856 ± 0.792 k2: 5.264 ± 0.209 m: 0.415 |
0.988 | 4.677 |
* n = 1 because the studied formulation is a film, in accordance to the theoretical model; ** the m value was extrapolated by the fitting analysis; *** the m value was calculated after the determination of the aspect ratio (2a/l = diameter/thickness) by consulting Figure 1 reported by Peppas and Salhin (1989). As here reported, data were curve fitted until the first 60% of ROP was released.