UK, United States of America. Transdermal patches. Each patch
contains a hydrogel type material in which an active drug is
formulated, together with a battery and a microprocessor. When
an electrical current is passed through the gel it repels the
drug and pushes it through the skin into the blood vessels. The
technology: known as iontophoresis: has been shown to be
effective in enhancing the delivery of agents with low intrinsic
skin permeability, such as peptides and other highly water
soluble molecules. The patch could be programmed to deliver the
drug continuously or in pulses. A study has shown that the
increase in systemic blood levels of the drug was proportional
to the current applied. The technology is limited to small
peptides (molecular weight 5,000 or less). For a drug with a
molecular weight of around 300, approximately 20-50 mg per day
could be delivered by iontophoresis, the limiting factor being
the amount of electrical current which could be tolerated. Key
areas for which the patches are bein