An assessment of the relationship between vasoconstrictor assay findings, clinical efficacy and skin thinning effects of a variety of undiluted and diluted corticosteroid preparations

A prospective study on patterns of topical steroids self-use in dermatophytoses and determinants predictive of cutaneous side effects

Nonprescription use of topical corticosteroids (TCS) is a significant concern. This can lead to cutaneous adverse effects, altered morphology of skin disorders and chronicity of cutaneous infections. To record and analyze the patterns of TCS use in patients with tinea corporis/cruris and analyze factors determining the development of cutaneous side effects. Hundred patients with a clinical diagnosis of tinea corporis/cruris who could recall the TCS preparation/s used were included. The TCS usage patterns were recorded and analyzed. Most patients had used very potent TCS (n = 66). Most reported using TCS intermittently for duration ranging from 1 to 4 weeks (n = 78). Relapse of symptoms occurred within 1 to 2 weeks of stopping TCS, triggering reuse. Cutaneous adverse effects were present in 44 patients (striae [n = 29], hypo/depigmentation [n = 11], skin thinning [n = 8], hypertrichosis [n = 1], tinea pseudoimbricata [n = 1]). There was a significant correlation between presence of cutaneous adverse effects and the total duration of TCS use (P = .0016), duration of disease (P = .016), and total amount of TCS used (P = .012). Use for >60 days and of >32 g were associated with 89% and 96.3% (respectively) probability of developing cutaneous adverse effects. Self-use of TCS is a worrisome trend. Intermittent use is a plausible reason for development of cutaneous side effects in only 44% patients.

In vitro penetration through the skin layers of topically applied glucocorticoids

Corticoids are actives widely used in the treatment of skin diseases. This work aims to study the penetration of 3 corticoids (betamethasone, clobetasol, and flurandrenolide), their relationship with their Log D values and the effects of the vehicles. The 3 compounds were applied on a Franz-type diffusion cell in propylene glycol solution and their respective commercial creams and ointments. The active amounts found in the stratum corneum, epidermal, and dermal layers of the skin were investigated. Their diffusions were greatly affected by the formulation; moreover higher amounts of substance in the epidermis and dermis were detected in ointments than in creams. The enhancement effect of propylene glycol was also observed. The differences between the 3 substances could be related to their lipophilicity, molecular structure, and molecular weight. The more hydrophobic compounds (clobetasol and betamethasone) are present in higher amounts in the epidermis and dermis, while the hydrophilic compound (flurandrenolide) is mostly present in the receptor fluid.

The skin-blanching assay

The skin-blanching assay is used for the determination and bioequivalence of dermatologic glucocorticoids (GCs). The exact mechanism of the production of blanching is not fully understood, but it is considered that local vasoconstriction of the skin microvasculature and the consequent blood-flow reduction cause this phenomenon. Several factors influence skin blanching, including drug concentration, duration of application, nature of vehicle, occlusion, posture and location. The intensity of vasoconstriction can be measured in several ways: visual or quantitative methods, such as reflectance spectroscopy, thermography, laser Doppler velocimetry and chromametry. In literature, contradicting results in the correlation of the skin-blanching assay with different tests to determine GC sensitivity have been reported, limiting its clinical usefulness.

Eumovate (clobetasone butyrate 0.05%) cream: a review of clinical efficacy and safety

Topical steroid creams and ointments have been available as over-the-counter (OTC) medications for the self treatment of acute dermatitis and other steroid responsive skin disorders for more than ten years. Despite earlier fears, widespread availability and use of these creams is not associated with clinically significant adverse effects. In dermatological practice, hydrocortisone 1% remains the mainstay of treatment for facial eczema, but it is often not effective in eczema affecting other body areas. Eumovate(TM) (clobetasone butyrate 0.05%) cream has recently been made available as a pharmacy medication for the short-term management of acute eczema and allergic dermatitis by adults and children aged 10 or older, based on evidence derived from clinical trials involving over 3500 patients. This review summarises the key efficacy and safety data derived from 29 clinical trials and the post-licensing pharmacovigilance safety information, which supported the reclassification of this product for OTC use. These data show clobetasone butyrate 0.05% is more effective than 1.0% hydrocortisone in the treatment of eczema and more effective than flurandrenolone 0.0125% (p=0.01%) and a potent topical steroid hydrocortisone butyrate (p<0.05), in the treatment of psoriasis. A review of the effect of topical steroids on skin thickness concluded that, following short term application, there was no clinically significant difference between hydrocortisone 1.0% and clobetasone butyrate 0.05% in terms of potential for skin thinning. Similarly, even under extreme conditions, clobetasone butyrate 0.05% has negligible systemic absorption and has almost no effect on HPA axis function.

Comparison of skin stripping, in vitro release, and skin blanching response methods to measure dose response and similarity of triamcinolone acetonide cream strengths from two manufactured sources

The collective studies compare in vitro drug release, in vivo skin stripping, and skin blanching response methods for dose responsiveness and bioequivalence assessment of triamcinolone acetonide cream products, as a function of application duration, drug concentration, and manufacturer source. Commercially available triamcinolone acetonide creams (0.025%, 0.1%, and 0.5%) from two manufacturers were evaluated in vitro for rate and extent of drug release across synthetic membranes and in vivo for rate, extent, and variability of drug uptake into human stratum corneum and skin blanching response in human forearm skin. Data demonstrate that increasing triamcinolone acetonide cream concentration applied increased the rate and extent of drug released in vitro as well as the extent of drug uptake and skin blanching response in human skin in vivo. No difference (p < 0.05) between the two sources of 0.1% or 0.5% creams was measured by the skin stripping or skin blanching response methods. Dermatopharmacokinetic analysis of triamcinonide acetonide in vivo is therefore dose responsive to drug concentration applied and application duration and agrees with in vivo skin blanching results. Data support the use of dermatopharmacokinetic methods for bioequivalence and bioavailability assessment of topical drug products.

Analysis of chromameter results obtained from corticosteroid-induced skin blanching assay: comparison of visual and chromameter data

In a Guidance document, the American FDA recommends the use of a Minolta chromameter rather than the human eye for the quantitative assessment of the pharmacodynamic blanching response produced by topical application of corticosteroids. The purpose of this study was to compare the appropriateness of the human eye and two models of chromameter for the estimation of skin blanching, in terms of the quality of the data generated by each method. The corticosteroid-induced skin blanching from four different betamethasone 17-valerate cream formulations was compared in a typical human skin blanching trial. The optimized assay methodology routinely practised in our laboratories was utilized. The blanching responses were assessed visually by three trained, independent observers and recorded by two chromameters (Minolta model CR-200 and model CR-300). The topical availability of the four creams was determined using visual scoring and chromameter measurements. All data were manipulated in such a manner as to produce a blanching response versus time profile from which AUBC analysis could be performed. Good correlation was observed between the visual assessments made by three independent observers. In contrast, moderate correlation was determined between visual, CR-200 and CR-300 measurements. Surprisingly, no direct linear relationship between the AUBCs produced by the two chromameters was observed indicating that the quality of the data obtained from the two instruments may not be equal. This investigation also indicated that the use of the chromameter is not completely objective. Visual scoring and chromameter measurement produce data sets that differ in quality. Each procedure needs to be validated and investigators have to be trained for both visual assessment and the operation of the chromameter, particularly with regard to the manipulation of the measuring head of the instrument.

Parallel intraindividual evaluation of the vasoconstrictory action and the anti-allergic activity of topical corticosteroids

The human skin blanching assay is a well established method for ranking the efficacy of corticosteroids after epicutaneous application. Vasoconstriction is a pharmacological activity, which correlates well with the clinical efficacy, the intensity of skin blanching after a single application under occlusion corresponding, generally, to the clinical efficacy after repeated application without occlusion. However, in studies dealing with the comparison between the vasoconstriction assay and the evaluation of the clinical effects on inflammatory skin diseases, some exceptions to this correlation have been reported. Therefore, in a pre-clinical phase, it would be useful to combine the blanching assay with at least one anti-inflammatory assay. In the present study the blanching assay and the allergic contact dermatitis inhibition test were performed in parallel, in order to compare the two testing procedures in the same group of subjects, utilizing standardized study designs supported by objective means of evaluation. Three commercial preparations of corticosteroids containing clobetasol propionate (CP), clobetasone butyrate (CB) and hydrocortisone acetate (HA), respectively, were employed both to treat nickel-induced positive patch test responses on the volar forearms, and to perform a vasoconstrictor assay on normal forearm skin in 16 nickel-sensitized healthy volunteers. For evaluating skin blanching, we employed colorimetric measurements, whereas for the quantitative determination of the inhibition of the intensity of allergic patch test reactions, 20 MHz B-scanning supported by image analysis was used. Both colorimetric and echogenicity values enabled us to distinguish between the three corticosteroids (at the 17 h evaluation and the 64 h assessment, respectively). A fair correlation was noted between colorimetric and echogenicity values. Both testing procedures ranked the three corticosteroids in the expected order. Corticosteroid preparations should be compared using methods which allow different effects to be simultaneously monitored, without involving a high number of patients. We are proposing this double procedure for the parallel intraindividual evaluation of the vasoconstrictory action and the anti-allergic activity of topical steroids.

Chemical stability of fluocinolone acetonide ointment and fluocinonide cream diluted in emollient bases

The chemical stability of fluocinolone acetonide ointment and fluocinonide cream was studied when diluted in emollient bases. Fluocinolone acetonide ointment was diluted 1 in 4 with Unguentum Merck and Lipobase. Fluocinonide cream was also studied in these bases, with the addition of Metosyn Diluent, at dilutions of 1 in 4 and 1 in 10. Regression analysis gave the time for 5% degradation of fluocinolone acetonide at a dilution of 1 in 4 in Unguentum Merck and in Lipobase as 12 weeks in both cases. The lower 95% confidence bound of each regression line was used to set shelf lives, for additional safety, and gave values of 1 month for the Unguentum Merck dilution and 2 months for the Lipobase dilution. Fluocinonide dilutions were more stable than the corresponding fluocinolone acetonide dilutions, with no degradation detectable during the study. The base made no observable difference to stability. Shelf lives, based on the lower 95% confidence bound of the regression data, of more than 6 months would be feasible for all of the fluocinonide 1 in 4 dilutions studied and for the 1 in 10 dilution in Unguentum Merck. However, for fluocinonide 1 in 10 in Metosyn Diluent, a shelf life of only 6 weeks could be assured, due to there being more variation in the analytical results. There were insufficient data to determine a storage life based on the lower 95% confidence bound of the regression for fluocinonide 1 in 10 in Lipobase. More data would be required to determine if there was significant interbatch variation in the stability of the dilutions.

Cellular mechanisms of the steroid-induced vascular responses in the rabbit ear artery

1. In anesthetized rabbits, topical application of dexamethasone to the ear produced an initial vasodilation followed by a vasoconstriction with long delay (120 min). Diphenhydramine inhibited the former, but not the latter. 2. In isolated rabbit ear arteries, dexamethasone reduced the amplitude of contractions of smooth muscles produced by nerve stimulation, noradrenaline and high-K solution, only at high concentrations (> 10(-5) M). 3. The initial vasodilation induced by topical application of dexamethasone may be related to endogenous histamine, while the delayed constriction response may not be direct actions of steroid to smooth muscles.

Use of reflectance spectrophotometry in the human corticosteroid skin blanching assay

A reflectance spectrophotometric method for evaluation of the skin blanching response to topical corticosteroids was evaluated. This blanching response is used, for drug development and regulatory purposes, to assess potency and bioequivalence of topical corticosteroid products. The common method involves the use of a human rater to measure blanching response in the skin. This study evaluated an instrumental alternative to the human rater and used this method to measure the differences between a number of brand name and generic topical corticosteroid products (six creams and six ointments). Products were applied to the forearms of normal volunteers and the blanching responses were assessed after 6 and 16 hours in both occluded and non-occluded skin sites. Only the fluocinolone acetonide generic and brand name preparations were different from each other. The spectrophotometric method proved to be equivalent but not superior to the standard human observer method.

New approaches to assess topical corticosteroid bioequivalence: pharmacokinetic evaluation

An ideal method for measuring the bioavailability of topical corticosteroids should be simple, accurate, and adaptable to a variety of settings and should not require extensive special training to perform. Drug uptake into the stratum corneum, measured by tapestripping, is correlated with the pharmacodynamic response of skin blanching, observed in the vasoconstrictor assay. Differences in stratum corneum drug uptake can be objectively quantitated as a function of time, occlusion, dose applied, and vehicle. Tapestripping measurements are reproducible within individual subjects, but large interindividual variabilities may exist. The chromameter, a new technology, objectively quantitates color numerically and can be used to measure skin blanching as part of the pharmacodynamic response to topical corticosteroids. The chromameter offers an easy, objective method with which to quantitate the pharmacodynamic response of topical corticosteroids. Both methods allow a more mechanistic approach than currently used methods to investigate topical drug pharmacokinetics and pharmacodynamics.

Quantifying anti-inflammatory agents' potency by measurement of response to dinitrochlorobenzene challenge

Classical assays of topical corticosteroid potency based on the induction of vasoconstriction are unsatisfactory for a number of reasons. These include the doubtful relevance of vasoconstriction to immune inflammation, and more importantly, the inability to compare non-steroidal agents with corticosteroids. Here we describe a simple assay in which the inhibitory effect of agents upon delayed type hypersensitivity response to dinitrochlorobenzene can be quantified by measurements of reaction as skinfold thickness with Harpenden callipers. Using this system we have confirmed the greater potency of clobetasol propionate (Dermovate) compared with betamethasone valerate (Betnovate), but the evidence for an inhibitory effect of topical cyclosporin (10% cream) compared with base on this response is less convincing.

Feasibility of measuring the bioavailability of topical betamethasone dipropionate in commercial formulations using drug content in skin and a skin blanching bioassay

An in vivo technique has been developed which simultaneously compares a skin blanching bioassay with drug content in human stratum corneum following topical application of four 0.05% betamethasone dipropionate formulations. Bioavailability of drug from commercial cream and ointment formulations was assessed by quantification of drug content in tape-stripped stratum corneum and skin blanching in the treated skin site under occluded conditions. Tape-stripping removed stratum corneum to a varying degree between individuals but was consistent (35%) within an individual with all formulations, day to day. A correlation (r = 0.9935) between the amount of drug in the treated stratum corneum normalized for surface area and the corresponding skin blanching score was observed with four 0.05% betamethasone dipropionate formulations. Increasing the amount of drug in the tape-stripped stratum corneum correlated with an increased skin blanching score. Ointment formulations delivered more drug to the skin and produced greater blanching scores than the cream formulations. Topical corticosteroid content in the treated skin site can therefore be quantified and correlates well with the resulting pharmacodynamic activity.

Quantification of skin-colour changes induced by topical corticosteroid preparations using the Minolta Chroma Meter

The Minolta tri-stimulus colorimeter CR-200 was used to quantify the blanching effect of topical corticosteroids in a non-occluded vasoconstriction test. To investigate the influence of time on variations in colorimetric parameters, an initial series of measurements was performed on Day 1 on six predetermined sites on the ventral surface of the forearm of six healthy volunteers every 2 h over a 12-h period. The colorimetric values were shown to be site related but hourly variations occurred with similar profiles for all the sites. On Day 2, four topical corticosteroid creams, representative of their potency groups, as well as a base were applied in a randomized double-blind manner on five of the predetermined sites. Visual gradings and colorimetric measurements were carried out every 2 h over the following 12-h diurnal period and were continued on Day 3. The colorimetric parameters L* (luminance) and a* (colour hue ranging from green(-) to red(+] gave a rank order correlated to corticosteroid potency that showed superior discrimination compared to simple visual grading. In this study, L* was more discriminative parameter than a*. The Minolta Chroma Meter CR-200 appears to be a simple and accurate device for objectively measuring the blanching effects of topical corticosteroids.

Relation of application time to bioactivity of a potent topical glucocorticoid formulation

The vasoconstrictor assay in human beings was used to assess bioavailability during different time periods of exposure when 0.05% clobetasol propionate cream (Temovate) was applied and left on for periods of 0.5, 1.0, 1.5, and 16.0 hours and subsequently washed. Maximal responses were achieved by 1.5 hours of exposure, but there was no significant difference in intensity of vasoconstriction between 1.0, 1.5, and 16.0 hours of exposure before washing the sites. Exposures to 0.05% clobetasol propionate cream for 0.5 hour were not significantly different from 16-hour exposures to 0.05% fluocinonide cream, but exposures to 0.05% clobetasol propionate cream for 1.0, 1.5, and 16.0 hours all resulted in significant increases in vasoconstriction responses compared with fluocinonide cream applied and left on for 16 hours. Topical exposures to a superpotent topical steroid for a short time give vasoconstrictor responses equivalent to long time exposures.