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  • Terpenes in propylene glycol as skin-penetration enhancers: permeation and partition of haloperidol, Fourier transform infrared spectroscopy, and differential scanning calorimetry.

Terpenes in propylene glycol as skin-penetration enhancers: permeation and partition of haloperidol, Fourier transform infrared spectroscopy, and differential scanning calorimetry.

Journal of pharmaceutical sciences (2002-07-13)
H K Vaddi, P C Ho, S Y Chan
ABSTRACT

The respective alcoholic terpenes carvacrol, linalool, and alpha-terpineol were used at 5% w/v in propylene glycol (PG) to increase the in vitro permeation of haloperidol (HP) through human skin. The possible enhancement mechanism was then elucidated with HP-stratum corneum (SC) binding studies, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The greatest increase in the permeation of HP was achieved with linalool followed by carvacrol and terpineol. HP permeation with linalool was predicted to reach a therapeutic plasma concentration and therapeutic daily-permeated amounts. Carvacrol increased lag time, which was attributed to slow redistribution of the enhancer within SC. Carvacrol increased the partition of the drug to the pulverized SC. Pure PG extracted lipids from SC but less than that achieved by the terpenes in PG. Terpenes extracted lipids to a similar extent. An increase in bilayer cohesion in the remaining lipids present in the SC could be attributed to the alignment of terpenes within the lipid bilayer. The higher permeation with linalool was attributed to its molecular orientation within the lipid bilayer. Terpenes showed different rates of SC dehydration but did not change the percentages of secondary structures of keratin.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Propylene Glycol, meets USP testing specifications
Sigma-Aldrich
Propylene glycol, FCC, FG
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1,2-Propanediol, ACS reagent, ≥99.5%
Supelco
Propylene glycol, Pharmaceutical Secondary Standard; Certified Reference Material
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1,2-Propanediol, ReagentPlus®, 99%
Sigma-Aldrich
1,2-Propanediol, puriss. p.a., ACS reagent, ≥99.5% (GC)
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1,2-Propanediol, meets analytical specification of Ph. Eur., BP, USP, ≥99.5%
Supelco
1,2-Propanediol, analytical standard
Sigma-Aldrich
1,2-Propanediol, tested according to Ph. Eur.
Sigma-Aldrich
1,2-Propanediol, SAJ special grade, ≥99.0%
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1,2-Propanediol, SAJ first grade, ≥99.0%