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Figure 8.35 Characteristics of in vivo polymer erosion and metronidazole (MTZ) release from 50/50 CAP/Pluronic L101 films (with 10% metronidazole loading) in a dorsal rat model.

Reproduced from K. A. Gates etal., Pharm. Res., 11, 1605 (1994).

cavity and to release there 65 pg progesterone per day to provide contraceptive cover for one year. The Ocusert device and the Transiderm therapeutic system (also shown in Fig. 8.34) which are discussed in Chapter 9, are products of the Alza Corporation (USA) and rely on rate-limiting polymeric membranes to control drug release. The opportunities for prolonged release of drugs given by the oral route are fewer. The aim in oral dose forms is for controlled rather than prolonged release, so that dosage frequency can be reduced or so that side-effects resulting from fast dissolution of drug can be minimised. Ion-exchange resin-drug complexes have also been used, and drugs may also be embedded in hydrophilic or hydrophobic matrices.

Figure 8.36 Theoretical representation of a polymer matrix: changes during erosion (dark pixels = nondegraded areas, white pixels = degraded areas), where Xa (a rate constant) = 2.7 x 1007 s01 for a sample containing 50% polyanhydride CPP.

Reproduced from A. Gopferich et al., in Formulation and Delivery of Proteins and Peptides (ed. J. L. Cleland and R. Langer), ACS Symposium Series no. 567, ACS, Washington, 1994.

Figure 8.36 Theoretical representation of a polymer matrix: changes during erosion (dark pixels = nondegraded areas, white pixels = degraded areas), where Xa (a rate constant) = 2.7 x 1007 s01 for a sample containing 50% polyanhydride CPP.

Reproduced from A. Gopferich et al., in Formulation and Delivery of Proteins and Peptides (ed. J. L. Cleland and R. Langer), ACS Symposium Series no. 567, ACS, Washington, 1994.

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