Effects of polyoxypropylene 15 stearyl ether and propylene glycol on percutaneous penetration rate of diflorasone diacetate

PPG-11 and PPG-15 Stearyl Ether

The Expert Panel for Cosmetic Ingredient Safety reviewed newly available studies since their original assessment in 2001, along with updated information regarding product types and concentrations of use, and confirmed that PPG-11 and PPG-15 Stearyl Ether are safe as cosmetic ingredients in the practices of use and concentration as described in this report.

Enhanced in vitro percutaneous absorption and in vivo anti-inflammatory effect of a selective cyclooxygenase inhibitor using microemulsion

Celecoxib, a specific COX-2 inhibitor, was recently approved for the treatment of rheumatoid and osteoarthritis, acute pain, familial adenomatous polyposis and primary dysmenorrhea. Oral administration of celecoxib is effective against ultraviolet B radiation (UVB)-induced skin carcinogenesis; however, its clinical use is restricted because of its failure to block the characteristic cutaneous inflammatory response and lower availability at the site of inflammation. Topical application of celecoxib has been effective compared with oral in certain clinical conditions. The present study was undertaken to develop and investigate the development of microemulsion system (isopropyl myristate/medium-chain glyceride/polysorbate 80/water) for topical delivery of celecoxib. The pseudoternary phase diagram was constructed with constant surfactant concentration, and several compositions were identified and characterized by using dynamic light scattering. The in vitro permeation rate of celecoxib through rat skin was determined for microemulsions, microemulsion gel, and cream by using the modified Franz-type diffusion cell. In all formulations tested, celecoxib permeated more quickly, and the microemulsions increased the permeation rate of celecoxib up to 5 and 11 times compared with those of microemulsion gel and cream, respectively. Increasing the concentration of medium-chain mono-/di-glyceride in microemulsion imparted increased droplet size and viscosity and decreased diffusion coefficient. In vivo anti-inflammatory study suggested that the developed microemulsion formulations might serve as potential drug vehicle for the prevention of UVB-induced skin cancer.

Influence of phloretin on the skin permeation of lidocaine from semisolid preparations

The purpose of the present study was to determine the significance of phloretin on the topical permeation of lidocaine using different semisolid preparations as delivery systems. One hydrophilic and three lipophilic formulations were used. After estimation of the solubility of phloretin and lidocaine in the vehicles and analysis of the viscoelastic properties, standard diffusion experiments with Franz type diffusion cells through porcine skin were performed. Results indicate a general lidocaine enhancement by phloretin in the tested vehicles. The permeation was enhanced 1.39-fold in the hydrophilic formulation and between 1.25- and 1.76-fold in the lipophilic formulations.

Influence of microemulsions on cutaneous drug delivery

In attempt to increase cutaneous drug delivery, microemulsion vehicles have been more and more frequently employed over recent years. Microemulsion formulations have been shown to be superior for both transdermal and dermal delivery of particularly lipophilic compounds, but also hydrophilic compounds appear to benefit from application in microemulsions compared to conventional vehicles, like hydrogels, emulsions and liposomes. The favourable drug delivery properties of microemulsions appear to mainly be attributed to the excellent solubility properties. However, the vehicles may also act as penetration enhancers depending on the oil/surfactant constituents, which involves a risk of inducing local irritancy. The correlation between microemulsion structure/composition and drug delivery potential is not yet fully elucidated. However, a few studies have indicated that the internal structure of microemulsions should allow free diffusion of the drug to optimise cutaneous delivery from these vehicles.

A new method for estimating dermal absorption from chemical exposure. 3. Compared with steady-state methods for prediction and data analysis

PURPOSE

This paper compares unsteady-state and steady-state methods for estimating dermal absorption or analyzing dermal absorption data. The unsteady-state method accounts for the larger absorption rates during short exposure times as well as the hydrophilic barrier which the viable epidermis presents to lipophilic chemicals.

METHODS

Example calculations for dermal absorption from aqueous solutions are presented for five environmentally relevant chemicals with molecular weights between 50 and 410 and log10Kow between 0.91 and 6.8: chloromethane, chloroform, chlordane, 2,3,7,8-TCDD, and dibenz(a,h)anthracene. Also, the new method is used to evaluate experimental procedures and data analyses of in vivo and in vitro permeation measurements.

RESULTS

In the five example cases, we show that the steady-state approach significantly underestimated the dermal absorption. Also, calculating permeability values from cumulative absorption data measured for exposure periods less than 18 times the stratum corneum lag time will overestimate the actual permeability.

CONCLUSIONS

In general, steady-state predictions of dermal absorption will underestimate dermal absorption predictions which consider unsteady-state conditions. Permeability values calculated from data sets which include unsteady-state data will be incorrect. Strategies for analyzing in vitro diffusion cell experiments and confirming steady state are described.

Structure-activity relationship of 1-alkyl- or 1-alkenylazacycloalkanone derivatives as percutaneous penetration enhancers

Nine azacycloalkanone (5-, 6-, or 7-member ring) derivatives with an alkyl or alkenyl (terpene) chain (10, 15, or 20 carbons) were compared with 1-dodecylazacycloheptan-2-one (azone, 1) for their effects on the percutaneous penetration of 6-mercaptopurine (6-MP) through excised guinea pig skin. Pretreatment of skin with an enhancer markedly increased penetration and skin accumulation of 6-MP. Superior enhancing effects were observed for enhancers having a terpene chain of 10 carbons and an azacyclo ring with one carbonyl group. Enhancers with a C20 tail chain were less effective. Enhancer ring size had little effect on enhancing activity, whereas the increase in the number of carbonyl groups in the ring caused a decrease. Computer fitting of a penetration profile to Fick's diffusion equation gave two parameters corresponding to diffusion and partitioning of 6-MP. The diffusion parameter was little affected by pretreatment with an enhancer, whereas the partition parameter was markedly increased. This suggests that enhancement is determined by the ability to increase the drug partitioning into the skin and to enlarge the drug concentration gradient in the skin barrier. The primary skin irritation was examined with rabbit dorsal skin in vivo. The enhancers with an alkyl chain induced severer primary irritation (erythema and edema) than those with an alkenyl chain. From the balance between enhancing and irritating activities, it is concluded that 1-geranylazacycloheptan-2-one, 1-farnesylazacycloheptan-2-one and 1-farnesylazacyclopentan-2-one are favorable enhancers.

Evaluation of penetration enhancement of lidocaine by nonionic surfactants through hairless mouse skin in vitro

The effect of two nonionic surfactants (polyoxyethylene sorbitan monoesters) on percutaneous absorption of lidocaine in the presence of various concentrations of propylene glycol is reported. Comparisons were made in vitro using excised hairless mouse skin as the barrier membrane. Under infinite dose conditions, steady-state flux was enhanced by surfactants at high propylene glycol concentrations. The same trend was observed following application of a thin layer of formulation to the skin (finite-dose conditions). However, penetration behavior was complex due to: (a) changes in vehicle composition following application, (b) temperature changes resulting from evaporation or moisture uptake, and (c) depletion of lidocaine as a result of penetration with compositions that lost water by evaporation. Two peaks in the flux versus time curve were observed. Surfactant monomer concentration in the vehicles was increased in the presence of propylene glycol.

An evaluation of once-daily applications of diflorasone diacetate in eczematous dermatoses

The efficacy of once-daily applications of 0.05% diflorasone diacetate in a cream or ointment formulation was evaluated in a 3-week study of 301 patients with eczematous dermatoses. The lesions were classified by severity and included those of an acute, sub-acute or chronic nature. Clinical evaluations were based on overall lesion improvement and improvement in specific signs and symptoms. Over 80% of patients reported the therapy to be good or excellent. Sixteen patients reported side-effects consisting largely of transient burning and stinging.