Pharmaceutical and medical applications of polymer electrolytes

Abstract

Abstract. Classic methods of drug delivery have embraced a number of routes into the site of pharmacological action. Modem preference, wherever possible, is for a non-invasive route to minimise the chance of cross infection, especially of the AIDS virus. The skin, which is the largest organ in the human body, is a particularly appealing route as, in the absence of wounds and blemishes, it offers a natural, high-integrity, barrier to the outside world. Skin patches containing active drug that is allowed to diffuse passively across the external skin barrier into the bloodstream now enjoy wide application but a problem is that the rate of egress is often slow.For certain ionic drugs, including local anaesthetics and, more recently, peptides and gene-based, biotechnological engineered pharmaceuticals, it is possible substantially to enhance transdermal transport by iontophoresis. The technique of iontophoresis facilitates the passage of ionic drugs through the skin using an electric current. IonicaUy conducting polymers (polymer electrolytes) are potential candidates as hosts for drugs to be delivered iontophoreticaUy.Key issues affecting iontophoretic delivery are reviewed in this paper and the potential role of polymer electrolyte materials in iontophoretic devices will be described.

Medical applications of solid state ionics

“…The term iontophoresis was introduced for this process in the 19 th century [10]. A variety of power sources has been used for iontophoresis [6,7,11,12] and for related processes such as electroporation [13]. External power sources have also been used to control drug delivery from implantable reservoirs [1] in order to improve patient compliance with a given therapy, the relative ease of self-dosing eliminating the need for multiple intravenous injections [14].…”

“…This is externally mounted on the skin and the drug, which has to be ionic for this application, is driven into the bloodstream transdermally by the application of a voltage from an external power source. Developments of a range of iontophoretic and related devices have been discussed elsewhere [6,7] and recent advances are outlined in section 4.…”

Biomedical applications of batteries

“…It can be used for controlled delivery and for non-invasive monitoring, as counter ions leave the skin to compensate for the charge of inserted drug ions [1,7,11,12] …”

“…The first is where devices and power sources are external to the part of the body where the particular equipment functions, as is the case with a transdermal iontophoretic device [1]. The second is where the device can be implanted at the site of action and the battery is either external or implanted in a different but convenient location.…”

“…It can be used to deliver neutral or cationic drugs, skin being negatively charged, but it is not useful for peptide or nucleotide drugs, which are anionic. Diffusion is not involved [1,9,16] • Reverse iontophoresis in which body fluids can be sampled by electro-osmotic flow sampling from the body [17][18][19] There are many subtle variants and combinations of electrically assisted transdermal methods such as a.c. [20] and switching [21] iontophoresis and jet injection combined with iontophoresis [22]. A variety of drugs can be iontophoretically delivered, including lidocaine for local anaesthesia [23] and acetic acid for tendonitis of the shoulder [24].…”