Release Characteristics of Implantable Cylindrical Polyethylene Matrices

Abstract

The geometrical relationship between a hemisphere and a cylinder has been investigated for controlled-release systems. The relationship was tested by comparing dissolution results with results from mathematical calculation based on the principles of diffusion for matrix systems. A procedure has been developed for producing implantable, cylindrical, low-density polyethylene matrices, uncoated or coated with a thin impermeable film and a thick paraffin layer except for a hole on the flat faces of the cylinder. Drug matrices were prepared from a blend of sodium salicylate and polymer compressed in an appropriately designed stainless-steel mould at 150 degrees C. Differential scanning calorimetry revealed that no decomposition product was formed in the matrix. When the surface area and the number of holes is increased, drug release also increases. When density is increased, however, drug release decreases significantly. Zero-order drug release was obtained from high-density covered one-hole and two-hole matrices. The diffusion coefficient was calculated as 0.067 day-1. The study suggested that true zero-order drug release could be obtained by drug diffusion from a hole, rather than from geometric shapes in the matrix systems. In addition, for constant release the diffusion area has to increase by approximately 25 mm2 every day, compared to the area of the previous day, because the diffusion distance increases logarithmically.

Two-Dimensional Solution and Analysis of a Cylindrical Matrix Device With a Circular Release Area

“…The product is coated so that there is no mass exchange with the environment except for a small release hole pierced in the top of the cylinder. This technology is of interest because several studies have proposed cylinder-with-opening type designs to obtain a desired delivery rate (Ertan et al, 1997(Ertan et al, , 2005; Hsu et al, Tojo and Miyanami (1983) and Figure 1 in Tojo (1984)). …”

Three-dimensional analyses of a perforated cylindrical drug delivery device

“…This approach can be applied to drug loaded in a cube. The method does not extend to implantable cylindrical matrices with release holes located on the surface of the design (Ertan et al, 1997;Hsu et al, 1992). Even with the assumption of angular symmetry, the concentration distribution is not easily obtained through the above-mentioned technique (Simon and Ospina, 2012).…”

Innovations in biotechnology

“…: starch, cellulose) as well as synthetic polymers are used e.g. : polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, polyacrylic acid, polycarbophile, polyacrylamides, polyacrylates, polyethylene glycol, poly(amino amide)s, polyurethanes, siloxanes, homoor copolymers of lactide and glycolide, poly(ε-caprolactone), polyorthoesters (Cardamone et al, 1997;Ertan et al, 1997;Huang et al, 1994;Lan et al, 1996;Matthews et al, 1996;Merkli et al, 1998;Ouchi & Ohya, 1995;Schierholz 1997;Sintzel et al, 1996;Uhrich et al, 1999;Ulbrich et al, 1996).…”