ABSTRACT
Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbruecken,
Germany
B. C. Lippold
Institute of Pharmaceutics and Biopharmaceutics, Heinrich Heine University, Duesseldorf,
Germany
C. S. Leopold
Department of Pharmaceutical Technology, Institute of Pharmacy, University of Hamburg,
Hamburg, Germany
SEMISOLID FORMULATIONS
Effects of Vehicles and Penetration Enhancers
After cutaneous administration of formulations such as ointments or creams, drug,
vehicle, and the skin may affect the penetration process and thus drug action in
different ways. Tronnier’s triangle (Fig. 1) (1) serves as model to illustrate these
relationships. Drug and vehicle are the components of cutaneous formulations,
which may be divided into those intended for transdermal absorption and systemic
action of the drug, those for regional effects in deeper tissue layers (e.g., joints)
and those for action on or in the skin (local action) (2). Formulations intended for
systemic drug action require therapeutic plasma levels of the drug. The use of
transdermal patches, which remain on the skin for an extended period of time,
allows inmost cases a zero-order drug input kinetic and thus constant plasma levels
over the whole application time period (3). While formulations with regional
action require drug penetration into deeper skin tissues with minimal systemic
action, for formulations with local action systemic action is undesired. In the
latter case, drug penetration into the skin may be slow but accompanied by a
high substantivity.
