TOPICAL ACTIVITIES OF BETAMETHASONE ESTERS IN MAN

Practical and scalable synthesis of beclomethasone dipropionate

Beclomethasone dipropionate (1) is a synthetic corticosteroid with anti-inflammatory, antipruritic, and anti-allergy properties. It is widely used to treat asthma, allergic rhinitis, and dermatoses. However, existing synthetic routes to this active pharmaceutical ingredient (API) contain steps resulting in low and/or inconsistent yields, and use obsolete reagents. Such inconsistencies coupled with a lack of reliable experimental data makes laboratory-scale and large-scale synthesis of this API difficult and time-consuming. In this paper, we report a practical and scalable approach to synthesize 1 from the readily available steroidal intermediate, 16β-methyl epoxide (3, DB-11). A gram-scale to kilogram-scale synthesis of 1 was achieved with 82% yield, using a cost-effective and scalable methodology. Selective propionylation of the hydroxyl groups at C₁₇ and C₂₁ demonstrate the fact that this approach can be conveniently implemented in fine chemical industries.

A Novel Approach to Assess the Potency of Topical Corticosteroids

The potencies of topical corticosteroid products have mainly been classified using clinical data but in some instances, the US Food and Drug Administration’s (FDA’s) vasoconstrictor assay (VCA) to assess the skin blanching response has also been used. However, the reported skin blanching response data were often based on a single visual reading and lack information on the dose (amount/quantity) or dose duration. Although several lists classifying potencies of various topical corticosteroid products have been published, the inherent potencies of topical corticosteroid raw materials used as active pharmaceutical ingredients (APIs) have not been investigated. The objective was to rank the inherent potencies of topical corticosteroid APIs and to standardize dosing such that the relevant compounds could be compared on a normalized molar basis. The potencies of clobetasol propionate, halcinonide, mometasone furoate, and fluocinolone acetonide were compared using the resulting E_max data following the fitting of the relevant response data to the E_max model where mometasone furoate > fluocinolone acetonide = clobetasol propionate > halcinonide. This ranking lists the respective inherent potencies of the APIs, which will facilitate the choice of a suitable candidate for incorporation into an appropriate topical corticosteroid product for a specific clinical indication.

Betamethasone Dipropionate (Diprosone): A New Topical Steroid. A Multinational, Multicenter Evaluation

A new fluorinated steroid, betamethasone dipropionate, has been used in ten studies in 413 patients (118 psoriasis; 295 other steroid responsive dermatoses). After three-weeks treatment with 0·05% betamethasone dipropionate cream, 87·90% of patients (363) showed a complete remission or were much better, while 11·38% (47) were slightly better. A total of 116 (98·31%) of patients with psoriasis and a total of 263 (89·16%) patients with other steroid responsive dermatoses were in complete remission or slightly better. An interesting feature is the rapidity of onset of action which occurred in 53% of the patients by the second day, and by the third day 91-100% of the patients had shown some improvement. Side-effects were minor and negligible (1·6%). These results indicate that betamethasone dipropionate is an effective and safe topical steroid for dermatological use.

Clinical Evaluation of a Non-Fluorinated Topical Corticosteroid: Prednisolone 17-Valerate, 21-Acetate

Prednisolone 17-valerate, 21-acetate (Acepreval), a new non-fluorinated topical corticosteroid, was clinically tried in 146 dermatological patients. Double-blind paired comparison studies, performed in subjects presenting bilateral, symmetrical dermatoses, showed that 0·3% Acepreval was significantly (p < 0·05) more effective than 1% hydrocortisone and as effective as 0·1% betamethasone 17-valerate. In open studies, performed in patients suffering from skin diseases of various kind, Acepreval gave good to excellent responses in 88% of the cases.

In vivo human skin permeability enhancement by oleic acid: a laser Doppler velocimetry study

Topical application of a skin permeation enhancer such as oleic acid (OA) can result in: (i) higher skin permeability for many exogenous substances (ii) an irritation reaction. Laser Doppler velocimetry (LDV) is one of few techniques which can assess both effects using appropriate protocols. Direct LDV measurement, measuring cutaneous blood flow, has been preferred as a tool to evaluate skin irritation. By comparing the LDV value of an irritant-treated site with an untreated site, an irritation index for the irritant can be obtained. Occlusive application of 0.16 M OA in propylene glycol (PG) for either 3 or 24 h produced irritation in form of redness and slight swelling. Using LDV, we obtained an irritation index of 2 and 4, respectively. The vehicle, PG alone, produced an index of around 1, which corresponded well to the slight to almost no irritation observed visually. The duration of the high irritation index assessed by LDV after OA-PG application is comparable to the duration of the increase in transepidermal water loss following the same application. This indicates a correlation between skin irritation and barrier perturbation caused by OA. LDV can also be used to elucidate the effect of enhancers on skin using hexyl nicotinate (HN) as a model drug, since its vasodilative effect can be clearly assessed by LDV. Pre-treatment of PG for 3 h significantly reduced the t0 and tmax of HN. No further reduction could be observed when OA was added into PG, suggesting that OA-PG is not more effective than PG alone in enhancing the permeation of HN.

Sensitivity of different areas of the flexor aspect of the human forearm to corticosteroid-induced skin blanching

The intensity of corticosteroid-induced blanching has been found to vary at different areas of the flexor aspect of the human forearm. A retrospective analysis of 38,880 observations of skin blanching in 56 volunteers was conducted to assess the sensitivity of forearm skin to betamethasone 17-valerate. The mid-forearm appears to be more sensitive to the blanching response than do the areas close to the wrist or elbow. These results indicate that each preparation under evaluation should be applied to several sites along the forearm when using the human skin blanching assay in order to obtain an accurate comparative assessment of corticosteroid release from topical delivery vehicles.

Effects of topical ammonium lactate on cutaneous atrophy from a potent topical corticosteroid

BACKGROUND

Topical corticosteroids produce atrophic changes in skin, including thinning of the epidermis and decrease in dermal ground substance. We observed that 12% ammonium lactate produced an increase in the thickness of epidermis and increased amounts of dermal glycosaminoglycans.

OBJECTIVE

Our purpose was to determine whether 12% ammonium lactate could minimize cutaneous atrophy produced by a potent topical corticosteroid.

METHODS

Clobetasol propionate, 12% ammonium lactate, and both agents were repetitively applied under occlusive patches as well as in open patches on the forearms of human volunteers for 3 to 4 weeks. Biopsy specimens were analyzed for thickness of the epidermis and dermal glycosaminoglycans by image analysis.

RESULTS

Twelve percent ammonium lactate produced a significant sparing of atrophy in both the epidermis and dermis without any influence on the bioavailability or antiinflammatory properties of the corticosteroid.

CONCLUSION

Twelve percent ammonium lactate may be useful in mitigating the adverse effects of corticosteroid on skin.

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.

New potent topical anti-inflammatory steroids with reduced side effects: derivatives of steroid-16-carboxy esters

Therapeutic use of anti-inflammatory steroids is limited due to their potential suppressive effects on pituitary-adrenal function and the immune system. Based on the antedrug concept, a new class of potent locally active compounds with reduced risk of side effects has been synthesized from prednisolone by introducing a metabolically labile methoxycarbonyl substituent at C-16. Results of topical application of the lead compound, methyl 11 beta,17 alpha,21-trihydroxy-3,20-dioxo-pregna-1,4-diene-16 alpha-carboxylate (P16CM;1), showed that it was 14 times more potent than prednisolone and that it had a greatly reduced tendency to cause systemic side effects. In the present investigations, we have demonstrated that chemical modifications such as 17- and/or 21-esterifications and 17,21-acetonidation of 1 further enhance topical activity in the croton oil ear edema model in rats. Following multiple topical ID50 applications of 1 or its derivatives, no thymolysis was noted. In the carrageenan-soaked sponge model of acute inflammation, all derivatives were potent inhibitors of leukocyte migration, generation of PGE2, and release of elastase. Taken together, these results indicate that esterification or acetonidation of hydroxyl groups at the 17 and/or 21 position, in combination with a labile C-16 methoxycarbonyl group, increases topical activity without concomitantly increasing the risk of side effects.

Bioequivalence (bioavailability) of generic topical corticosteroids

A new, quantitative modification of the vasoconstrictor assay was used to measure bioavailability of generic topical corticosteroid products in two categories: betamethasone valerate 0.1% cream and triamcinolone 0.1% cream. Betamethasone valerate products could be separated into two distinct categories, and triamcinolone acetonide products could be grouped into three categories of activity. A survey of local pharmacies showed that generic substitution would be made for the prescribed brand of betamethasone valerate in 58% of cases and for the prescribed triamcinolone acetonide 75% of the time. Because of the prevalence of generic substitution of products that may not have equivalent bioavailability, some standardization of the bioavailability of topical products is needed.

The use of GLIM and the bootstrap in assessing a clinical trial of two drugs

An approach is described for estimating the dose of a new drug which is equipotent to an established dose of an old drug. The approach is basically that of the parallel-line assay but it can allow for concomitant variables and, by exploiting the facilities available in the statistical computer package GLIM (generalized linear interactive modelling), the approach can be applied when the residuals conform to one of a number of distributions and, with suitable safeguards, to continuous, discrete and even 'scored' responses. In some circumstances, it is necessary to obtain confidence limits by Efron's 'bootstrap' technique. The method is illustrated with results from a trial of two premedicant drugs in children.

Enhancement of affinity to receptors in the esterified glucocorticoid, hydrocortisone 17-butyrate 21-propionate (HBP), in the rat liver

To investigate the affinity of glucocorticoid (GC) to its receptor, the binding of [3H]hydrocortisone 17-butyrate 21-propionate ([3H]HBP) and [3H]dexamethasone ([3H]DEX) in rat liver was analyzed kinetically. Scatchard analysis of [3H]hydrocortisone ([3H]HC) binding yielded a curvilinear plot with upward concavity with high and low affinities. The dissociation constant (Kd) value of high affinity was 1.9 nM and of low affinity 68.7 nM. A Scatchard plot of [3H]HBP binding showed a straight line with high affinity. The Kd value was 9.8 nM. The Kd values for the low affinity site of HC were in good agreement with the Ki values obtained from displacement experiments of [3H]DEX and [3H]HBP binding. The Ki values of HC for [3H]DEX and [3H]HBP were 51.9 and 42.3 nM respectively. The association rate constant for HBP to the GC receptor was 2.9 times lower than that for HC. The dissociation rate constant for HBP was 6.1 to 8.3 times lower than that for HC. The Kd values for [3H]HBP (9.5 nM) and [3H]HC (30.0 nM) obtained from the above two rate constants were approximately the same as the Ki and Kd values (in the case of HC, the value of the low affinity site). These results suggest that esterification of the hydroxyl group(s) in the side chain of GC by butyrate and propionate increased the affinity to the GC receptor, and that a decrease in the dissociation rate from the receptor caused the increase in the affinity to the GC receptor.

Spatial variability of vasodilatation in human forearm skin

Vasodilatation elicited by topical application of methyl nicotinate was measured by photoplethysmography at various positions on human ventral forearm skin. The time-to-peak response, the magnitude of the peak response, the area under the response-time curve and the time for the response to decay to 75% of the maximum value, were recorded at six positions on the left and right forearms of eight subjects. There was no significant difference between response on the right and left forearm sites and no difference in response between the lateral and medial sites on the forearms. In a second experiment, the vasodilatation was measured at proximal and distal positions on the forearm. The magnitude of the peak response at the proximal position was significantly higher than that found distally (P less than 0.01) as was the area under the response-time curve (P less than 0.05). These results suggest a possible cause for the variation observed in vasoconstrictor assays of corticosteroids.

The effect on epidermal DNA synthesis of a combination of topical steroid with either dithranol or tar as used for psoriasis

The hairless mouse was used to investigate the effects of a combination of glucocorticosteroid with either dithranol or tar on epidermal DNA synthesis, in order to determine whether such combinations reduce epidermal DNA synthesis more effectively than the single agents. Dithranol alone produced a significant local inhibition of DNA synthesis at concentrations of 0.1% and 0.05% but not at lower concentrations. Dose-response data for dilutions of clobetasol propionate and betamethasone 17-valerate showed progressive diminution of both local and systemic effects with decreasing concentrations. An additive effect was found from combining clobetasol propionate with dithranol and from combining betamethasone 17-valerate with liquor picis carbonis. These combined preparations were tested again after storage for 6 months and 2 months respectively and showed no loss of efficacy. These results lend justification to the use of these combined preparations in the treatment of psoriasis.

Kinetics of decomposition and formulation of hydrocortisone butyrate in semiaqueous and gel systems

The stability of hydrocortisone butyrate in semiaqueous and formulated gel systems has been investigated. It was shown that hydrocortisone butyrate underwent reversible isomerization to the C-21 ester of butyric acid. This ester then hydrolyzed to hydrocortisone, which in turn degraded to a complex mixture of compounds. This step is metal catalyzed and can be inhibited by the addition of EDTA [disodium(ethylenedinitrilo)tetraacetate]. The kinetics of decomposition is modeled using nonlinear regression analysis, and the rate constants for the various decomposition pathways are quantified.

The stability and blanching efficacy of betamethasone-17-valerate in emulsifying ointment

The bio-availability of betamethasone-17-valerate (Betnovate ointment) in emulsifying ointment (1 in 4 dilution) was investigated in ten subjects using a single-application vasoconstrictor assay; the blanching induced was measured using a skin reflectance spectrophotometer. The vasoconstrictor activity of the diluted preparations decreased with age. There was no significant difference between the vasoconstrictor activity of freshly made Betnovate 1 in 4 in emulsifying ointment and undiluted Betnovate ointment, and between 3-4 week old diluted Betnovate and emulsifying ointment base. Blanching induced by freshly prepared 4, 8 and 16-fold dilutions was not significantly different but a large reduction in blanching occurred on diluting 32-fold with emulsifying ointment. The degradation of betamethasone -17-valerate in emulsifying ointment was quantified by high performance liquid chromatography. More than 60% of the betamethasone -17-valerate underwent degradation within 6 h. There was a simultaneous increase in the concentration of betamethasone-21-valerate which peaked within 2 days and was followed by a slow degradation (half-life 8 days) to betamethasone free alcohol.

Two simple methods for the evaluation of topically active anti-inflammatory steroidal ointments

Simple laboratory methods for quantitating the topical anti-inflammatory activity of steroidal ointments are described. One is of croton oil ear edema in rats and the other is a new method using homologous passive cutaneous anaphylaxis (PCA) in rats. In order to avoid problems such as the animals' licking and/or rubbing the ointment at the applied sites, which might result in oral uptake, each rat was housed individually and fitted with a plastic collar in the croton oil experiment. The sites of ointment application in the PCA experiment were covered with adhesive plaster. Optimal experimental conditions were as follows. In the former method, ointments were applied to the inside surface of the ear 5 min after the irritant treatment and anti-edematous activity was determined after 6 h. In the latter, ointments were applied 3 h before the antigenic challenge to the dorsal area of animals which had been passively sensitized by anti-serum, and inhibition of the increased permeability was determined 45 min after the challenge. These methods were found to be reliable with respect to sensitivity and reproducibility of data. Ointments of halcinonide, betamethasone-17-valerate, hydrocortisone-17-butyrate, fluocinonide, flumethasone-21-pivalate and beclomethasone-17,21-dipropionate were evaluated by these methods.

The effects of increased penetration of betamethasone dipropionate in a propylene glycol base (Diprolene) for psoriasis

The efficacy and safety of betamethasone dipropionate, 0.05% in a propylene glycol base (Diprolene), was investigated in an open, fixed-dose study of thirty-one patients with resistant psoriasis. Clearing of lesions or marked improvement occurred in 97% (thirty out of thirty-one) of patients. Increased penetration of corticosteroid did not cause adrenal suppression or other adverse reactions.

High-performance liquid chromatographic assay of betamethasone 17-valerate and its degradation products

A high-performance liquid chromatographic assay of betamethasone 17-valerate is described. The procedure may be use for quantitative assay of the degradation products, betamethasone 21-valerate and betamethasone, and the application to the analysis of ointments is described. The method is also suitable for the determination of the kinetics of decomposition from one experimental run, and the determination of rate constants from a four-compartment sequential reaction is described. The procedure is also applicable to other corticosteroids, and hydrocortisone 17-butyrate, hydrocortisone 21-butyrate, and hydrocortisone may similarly be determined without modification to the method.

The stability of betamethasone-17-valerate in semi-solid bases

The stability of betamethasone-17-valerate in semi-solid bases has been investigated. Emphasis has been placed on the stability problems which could arise upon dilution of proprietary preparations by the use of model systems. Betamethasone-17-valerate has been shown to decompose to betamethasone-21-valerate and betamethasone alcohol. Quantitation of the decomposition was by direct densitometry on thin layer chromatographic plates. The decomposition was found to be an apparent first order process and to depend on the diluent used and its concentration. Attempts were also made to relate the rate of decomposition to the pH of the base used, and to stabilize the products.

Assessment of topical anti-inflammatory activity in rats with cantharidin-induced inflammation

Topical application of 400 mug of cantharidin to the rat's ear caused an approximate doubling in the mean weight of uniform ear punch samples when compared to vehicle-treated controls at 72 hr, and produced a maximal response at 7 days. Dexamethasone reduced the increase in weight when applied topically, but was ineffective when given subcutaneously or orally at the same doses. Hydrocortisone, prednisolone, triamcinolone, betamethasone, flurometholone, paramethasone acetate, fluocinolone acetonide, fluocinonide, and flurandrenolide showed significant suppression of cantharidin-induced inflammation. Cholesterol, diphenhydramine, tripelennamine, chlorpheniramine, promethazine, cyproheptadine, epinephrine, phenylephrine, alpha-tocopherol, indomethacin, and bufexamac were inactive. It is suggested that the procedure employed may be useful in the screening and evaluation of topical anti-inflammatory agents.

The effect of clobetasone butyrate and other topical steroids on skin thickness of the domestic pig

A new glucocorticoid, clobetasone butyrate, has been shown in patients to have good topical anti-inflammatory activity and a minimal effect on hypothalamic-pituitary-adrenal function. Among a group of topically active corticosteroids, compared in a controlled study in the domestic pig, clobetasone butyrate is shown to cause less epidermal thinning than any of the others except only 1% hydrocortisone. This evidence of a lesser atrophogenic effect may indicate further dissociation of unwanted from wanted properties in clobetasone butyrate.

The clinical assessment of topical corticosteroid activity

Glucocorticoid-induced vasoconstriction of human skin has provided a useful guide to topical anti-inflammatory activity. The concentration and base in which a steroid is used influence this activity, and traditional greasy ointments are probably the most effective vehicles. Confirmation of clinical effectiveness should be by double-blind comparison in patients with bilateral skin lesions. Psoriasis provides a more discriminating test of steroidal activity than eczema; the use of occlusive dressings may mask differences between compounds. Short-term trials are informative but in patients with chronic diseases, longer studies should also be done.

Intranasal betamethasone valerate in the treatment of seasonal rhinitis

Betamethasone valerate aerosol given in doses of 100 mug into each nostril twice daily was compared with a placebo in a double-blind, cross-over trial involving thirty patients with seasonal rhinitis. Patients recorded symptoms of eye irritation and watering, sneezing, rhinorrhoea, and nasal blockage, on a diary card. Analysis of the symptom scores showed that nasal symptoms were significantly better on betamethasone valerate than on placebo (P less than 0.01) and that nasal blockage in particular was improved (P less than 0.001). The patients' preference was significantly in favour of the active compound (p less than 0.02) and no side-effects were noted. It is concluded that betamethasone valerate offers a safe and effective form of treatment for seasonal rhinitis.

Vasoconstrictor activities of some novel synthetic steroids in alcoholic solution

Ethanolic solutions of 8 new, topically active, anti-inflammatory steroids and 1 standard (betamethasone 17-valerate) were assessed with a modified vascoconstrictor assay. Pallor was graded at 17 reading times for determination of complete blanching curves. The compounds were ranked by three methods: (1) summed % total possible score, (2) area under the blanching profile, and (3) square root transformation of sum of scores divided by number of volunteers, for statistical differentiation of the solutions. Conclusions on structure-vasoconstrictor activity relationships were that substitution or removal of 21 hydroxy provided compounds with a wide range of activity. Poor activity correlated with a hemisuccinate salt grouping at position 21, or the absence of 11beta-hydroxy.