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Biopharmaceutics of mucodermal resorption

If a systemic effect is desired, the medication must either be directly injected into the bloodstream or administered in an absorbable way. The condition or age of the patient is quite often an influencing factor when selecting the type of administration. Unconscious patients cannot be administered any medication orally (risk of aspiration.) Also patients with stomach complaints or limited intestinal function are not very suited for oral administration. On the other hand, injections are often avoided with patients afraid of injections and with children. In addition, disadvantages of parenteral administration are the higher expenses and increased risk in case of unintended paravenous injection, vessel damage, injection too quickly, germ transfer and other sources of risk.

For more than 100 years now, the fast systemic effect of glycerol trinitrate has been recognized with sublingual therapy. However, sublingual and buccal therapies in pharmaceutical practice have played an unimportant role up to today although the mucous membrane is an almost ideal absorption location for medication despite the relatively small available surface area and high vascularization.

The real resorbtion barrier is the surface membrane of the cells. Today’s ideas concerning plasma membranes is most like the one of Lenard and Singer proposing a fluid-mosaic-model. According to their theory, the membrane consists of a lipid double layer. For the passage of the substance, there are two qualitative completely different membrane structures available: first, the lipid layer for the absorption of lipophile substances and the water-filled pores for the penetration of hydrophile substances. The mucous membrane of the mouth behaves like the remaining mucous membranes, namely like lipid membranes, and is hence mainly permeable for substances with a sufficiently high lipid or oil/water distribution coefficient. This means the active agent can be better absorbed in a non-ionized state. Experience has also shown that ionized and hence present medication in a hydrophile state can also release their effect, i.e. be resorbed. The resorbtion depends among other things significantly upon the contact surface, the contact time and the concentration gradients.


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Types of mucodermal application: