Membrane systems: theoretical aspects.
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Delayed-Action Preparations↗
Biomedical subjects
H K Lonsdale
Publications and source records attributed to H K Lonsdale.
Development of an estriol-releasing intrauterine device.
Estriol-releasing intrauterine devices were developed for experimental use in animals and humans. The devices consist of a reservior containing the steroid surrounded by a rate-limiting polyurethane membrane. After an initial transient, the drug is released from the device at a constant rate for 1 year or more; devices with a much longer release period can be fabricated readily. A constant release rate is achieved by maintaining solid drug in the reservoir and good physical contact between the drug and the inside wall of the device. The methods used to fabricate the devices are described along with release rate and stability data.
Chemistry, Pharmaceutical↗
The in vitro permeability of skin and buccal mucosa to selected drugs and tritiated water.
The permeability of whole human skin, human dermis, whole pig skin, and canine buccal mucosa have been determined for four chemically different solutes: tritiated water, amphetamine, estradiol, and ouabain. Several new in vitro techniques for isolation, preservation, and permeability determination of these membranous tissues are described. Water permeabilities of human epidermis and dermis using these techniques agree well with published results. Human and porcine skins are very similar with respect to water permeability, while buccal mucosa is similar to dermis in its permeability characteristics to the four representative test agents. The permeability of hydrated whole skin is determined by the permeability of the epidermis, and the dermis and buccal mucosa behave as if they are water barriers exhibiting a permeability of about 30% of the diffusion through pure water, a difference that can be ascribed to the porosity and/or tortuosity of the tissue matrix.
Amphetamines↗