Semisolid drug release from

Sustained Drug Release from Solid, Semisolid, and Liquid Formulations... 

Zatz, J.L., Drug Release from Semisolids Effect of Membrane Permeability on Sensitivity to Product Parameters." Pharmaceutical Research 2 787-789, 1995. 

SUPAC-SS—Drug Release from Semisolid Formulations... 

Drug release from suspension-type semisolid vehicles has been investigated by T. Higuchi (51) and is described by the now classical equation ... 

These effects were also confirmed for another drug, ibuprofen, by comparison of the drug release from different semisolid formulations into dodecanol collodion membrane (Figure 31.12) [15]. 

A modified Franz diffusion cell has been developed in our laboratory in order to simultaneously measure the amount of drug released by diffusion from a semisolid formulation and the amount of drug washed away by a fluid stream simulating the removal action exerted by... 

Solvent-induced gelation could be obtained for a water-insoluble polymer, dissolved in a biocompatible solvent to create an injectable solution. When the solution is injected the solvent diffuses out and water from the physiological environment diffuses in. This diffusion process leads to a phase transition for the polymer as it goes from the solvent phase to a nonsolvent phase and forms a semisolid gel (44). Several factors such as polymer crystallinity, hydrophilicity, and water uptake govern the sol-gel transition and subsequently the drug release characteristics. 

The key parameter for any drug product is its efficacy as demonstrated in controlled clinical trials. The time and expense associated with such trials make them unsuitable as routine quality control methods. Therefore, in vitro surrogate tests are often used to assure that product quality and performance are maintained over time and in the presence of change. A variety of physical and chemical tests commonly performed on semisolid products and their components (e.g., solubility, particle size and crystalline form of the active component, viscosity, and homogeneity of the product) have historically provided reasonable evidence of consistent performance. More recently, in vitro release testing has shown promise as a means to comprehensively assure consistent delivery of the active component(s) from semisolid products. 

The in vivo performance of sodium caprate depends on the delivery system and how the drug and sodium caprate are released. The oral bioavailability of a peptide, for instance, was enhanced in rats and dogs using capsules containing a semisolid matrix of sodium caprate, polyethylene glycol and water. In contrast, other formulations were less effective. The extent of absorption enhancement reported ranged from almost no improvement up to fivefold (Aungst et al. 1996 Burcham et al. 1995). 

Fig. 8 Illustration of the use of release rates from semisolid preparations to determine drug solubility within a formulation. Data show the release rates of benzocaine from propylene glycol/water gels as a function of drug concentration in the formulation. (Redrawn from Ref...

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