Download testing of different substances for their dermal penetration

TESTING OF DIFFERENT SUBSTANCES FOR THEIR DERMAL
PENETRATION ENHANCEMENT
U.F. Schaefer1, K. Elbert1, F. Ruchatz2
2
Department of Biopharmaceutics and Pharm. Technology, Saarland University, Im Stadtwald, D-66123 Saarbrücken, GERMANY
BASF Aktiengesellschaft, Dept. ME/DP - H201, 67056 Ludwigshafen
Segmentation of the skin 1 :
INTRODUCTION:
Over the past years, transdermal or dermal drug delivery has been gaining
more and more interest by manufacturers. In this context, for facilitated
drug penetration across the skin barrier, the stratum corneum , the search
for substances with penetration enhancement properties is intensified.
On the other hand, for cosmetic preparations, a reduction of the
penetration of substances, e.g. light protection filters is desirable. For this
purpose 5 substances were tested for their influence on the penetration
behavior of a lipophilic model drug, flufenamic acid, in excised human
skin.
MATERIALS AND METHODS:
Test substances: C remophor RH 40 ® polyoxyl-40-hydrogenated Castor Oil
Cremophor S 9 ® PEG-9-stearate
Soluphor P ® pyrrolidone-2
Propylencarbonat cyclic propylene carbonate
Citral FG ® 2,6-Octadienal
Skin Preparation:
Human skin of the abdominal region of female patients who had
undergone plastic surgery was used. Immediately after excision the
subcutaneous fatty tissue is removed, and the skin is cut into pieces (10 x
10 cm), wrapped in aluminum foil and stored in impermeable
polyethylene bags at -26°C until use. After thawing, a 25 mm diameter
disk of skin is transferred to the incubation apparatus
Test system and test settings:
Standardized stripping method for the stratum corneum :
• The skin is stripped over a teflon mask (diameter 15 mm) with adhesive tape (Tesafilm
K ristall klar® , Fa. Beiersdorf, Germany)
• The adhesive tape is charged with a weight of 2 kg. After 10 sec., the tape is removed
rapidly with forceps
• for analytical reasons the tapes are combined into pools of 1 to 5 strips
Segmentation of the viable epidermis and dermis:
• A biopsy (diameter 13 mm) is taken of the stripped area and mounted on a metal bloc
• The skin is cut parallel to the skin surface by using a freezing microtome (thickness of
cuts: 25 µm)
• For analytical reasons the cuts can be pooled
Analytical method:
• For drug extraction of the strips or cuts, 0.05 M aqueous Sodium hydroxide solution
is used
• A fter centrifugation, the supernatant is directly injected onto a RP-18 HPLC system
RESULTS:
In figure 1 the amounts of flufenamic acid found in the stratum corneum and deeper
skin layers are shown for the time point 1 hour. It is evident that at this time point
Soluphor P ® and Cremophor R H 4 0 ® enhanced the flufenamic acid content in the
stratum corneum 3-fold, 2-fold respectively. For the other substances no influence
could be detected.
In the deeper skin layers a reduction (5 to 3-fold) of flufenamic acid occures by all
substances expect Soluphor P ® which gives a 2-fold enhancement.
A t the time point 3 hours (figure 2) Citral FG ® , Soluphor P ® and Cremophor RH 40 ®
showed a penetration enhancement of approximately 1.8 to 2.5-fold in the stratum
corneum .
The amount of flufenamic acid after pretreatment with Soluphor P ® and C remophor R H 4 0 ® are on a lower level in the stratum corneum at this time point, which might
be caused by the diffusion of the test substance into the applied drug preparation.
In the deeper skin layers it can be clearly seen that Soluphor P enhances the flufenamic
acid amount to a 3-fold higher level in comparison to the control. For the other tested
substances relative small amounts of flufenamic acid are reached in the deeper skin
layers.
F igure 2: flufenam ic acid distribution after 3 hours
10000
flufenamic acid ng/cm²
1
8000
filter paper soaked
w ith the test substance
4000
2000
0
Reincubation with 0.9% flufenamic acid in wool alcohols ointment
(German Pharmacopoeia) for 1 hour and 3 hours, respectively
0,5 kg
0.9 % flufenamic acid
in wool alcohols ointment
excised human
skin from plastic
surgery
flufenamic acid ng/cm²
C leaning step
1
control
Propylencarbonat
C itral FG
CONCLUSION:
S tratum corneum
8000
6000
deeper skin layers
4000
2000
0
1
control
Propylencarbonat
C itral FG
Under the applied conditions Soluphor P ® could clearly be
detected as a penetration enhancer for the lipophilic model drug
flufenam ic acid. Cremophor R H 4 0 ® shifts the drug distribution
to the stratum corneum and Cremophor S9 ® hinders the
penetration of flufenam ic acid into deeper skin layers. Whether
these last mentioned effects are useful for cosmetic
formulations is to be shown by further studies .
2
Cremophor S9
Soluphor P
Cremophor RH 40
ACKNOWLEDGEMENTS:
The BASF, Ludwigshafen, Germany is thanked for financial support.
REFERENCES:
[1]Schaefer UF, Loth H, Pharm . Res. 13 1996 (Suppl.) 366
C leaning step
2
Cremophor S9
Soluphor P
Cremophor RH40
Figure 1: flufenam ic acid distribution after 1 hour
10000
excised human
skin from plastic
surgery
S tratum c o rneum
6000
Preincubation w ith the test substance for 1 hour using infinite dosing to
saturate the stratum corneum w ith the test substance
2 kg
deeper skin layers