Desoxymethasone: A Review of its Pharmacological Properties and Therapeutic Efficacy in the Treatment of Dermatoses

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Synopsis: Desoxymethasone1is a highly active, fluorinated corticosteroid with a chemical structure similar to that of dexamethasone, It is available for topical use in a concentration of 0.25% in a water-in-oil emulsion base described as being ‘slightly greasy’, and containing fatty acid esters, wool fat alcohols, paraffins and purified water, without preservatives.

In comparative studies in small groups of patients with inflammatory dermatoses, 0.25% desoxymethasone has often been judged superior overall to commercially available preparations (standard ointment or cream bases) of some other intermediate to high potency topical corticosteroids such as betamethasone valerate 0.1% or dipropionate 0.05%, fluocinolone acetonide 0.025 to 0.2%, fluocinonide 0.05%, triamcinolone acetonide 0.1%, etc, especially in patients with psoriasis in whom it might be expected that small differences in comparison drugs would become most apparent (as opposed to more readily responsive conditions such as eczema in which all effective treatments would likely appear similar). There are no published studies comparing desoxymethasone with the very potent topical corticosteroids clobetasol 17-propionate 0.05% or halcinonide 0.1%.

In both open and controlled studies a rapid onset of response to desoxymethasone, with marked symptomatic improvement frequently occurring sooner (within 2 to 3 days) than with some of the comparison drugs, such as betamethasone valerate 0.1% or dipropionate 0.05% and fluocinolone acetonide 0.2 to 0.025%, was often reported. There are no published studies on the rate of relapse of inflammatory dermatoses following initial improvement or ‘cure’ with desoxymethasone.

Whether the apparent advantages of desoxymethasone over other closely related topical corticosteroids represent inherent differences in the activity of the steroids themselves, or arise from differing properties of the water-in-oil emulsion base in which desoxymethasone is available compared with the standard ointment or cream bases in which the comparison drugs are commercially available for clinicians' use, cannot be firmly stated from present studies.

In most patients desoxymethasone has been well tolerated, although the adverse local and systemic effects which may occur with other topical corticosteroids have also occurred with it in some patients.

Pharmacology: In comparative experimental studies in volunteers, 0.25% desoxymethasone in the commercially available water-in-oil emulsion base was more active than the usual concentrations of other topical fluorinated corticosteroid drugs tested, such as betamethasone valerate (0.1%), fluocinolone acetonide (0.025%), triamcinolone acetonide (0.1%), etc, either in ointment bases (reduction of induced erythema test) or in identical water-in-oil emulsion bases (skin blanching test).

Systemic effects of topically applied desoxymethasone, characterised by reversible decreases in circulating eosinophils, 11-hydroxycorticosteroid serum levels and/or 17-hy-droxycorticosteroid urinary excretion, have been demonstrated after both occlusive and non-occlusive application of relatively large doses (up to 45g of the 0.25% preparation daily for several days) to normal or diseased skin, but such effects were most pronounced during occlusive treatment of diseased skin. Similar effects occurred with other halogenated corticosteroids tested.

Pharmacokinetics: The pharmacokinetics of topical application of desoxymethasone in man have received only limited study, and studies on the extent of absorption during repeated application to diseased skin have not been done. Following occlusive application to patients with bromhidrosis, but apparently without skin lesions, penetration into the epidermis and skin appendages occurred rapidly (evident within 30 minutes), although in I study 80% of an occlusively applied radiolabelled 8g dose of 0.25% desoxymethasone (water-in-oil emulsion base) remained on the skin surface of healthy subjects after 24 hours. Radioactivity excreted in the urine and faeces over the next 10 days corresponded to about 5% systemic absorption.

In rats, the liver and adrenal glands are the preferential organs of distribution following occlusive application. Although some metabolic and excretion studies have been performed in rats, such studies have not been done in man. In the rat some sex differences were observed in excretory patterns, urinary excretion occurring more slowly and to a lesser extent in females. However, in both sexes the total amount of faecal excretion was about 20% of urinary excretion.

Therapeutic Trials: Desoxymethasone has been studied in relatively large numbers of patients, most with either psoriasis, eczema or dermatitis, in short-term (usually less than 1 month) open trials, about 75 to 100% of such patients showing improvement during treatment. In most of these studies the results were reported for the group of patients as a whole, making it impossible to determine the relative response rate of different inflammatory dermatoses. Unpublished data suggest that a similar overall response rate occurs after longer-term (up to 20 months) treatment. The relative effectiveness of occlusive and nonocclusive methods of application have been studied in only a few patients in a single study, both treatment methods producing a similar rate of response when results for all patients with steroid-responsive dermatoses (about equal numbers with psoriasis and other inflammatory dermatoses) were reported together. Further studies are needed to clarify the effect of occlusion with desoxymethasone on the response rate in difficult to treat conditions such as psoriasis in which it is reasonable to expect that, as with other topical steroids, occlusion would improve the response rate.

In smaller groups of patients in controlled comparative trials (usually within patient, left side/right side comparisons), 0.25% desoxymethasone has often been judged superior overall to commercially available preparations of some other halogenated corticosteroids (betamethasone valerate 0.1% and dipropionate 0.05%, fluocinolone acetonide 0.2 or 0.025%, fluocinonide 0.05%, triamcinolone acetonide 0.1% or fluprednidene acetate 0.1%) and to hydrocortisone butyrate 0.1%, especially in patients with psoriasis; and was at least as effective as fluocortolone esters (0.5%) and diflucortolone valerate (0.1%). In several studies the onset of marked symptomatic improvement was reported to occur more rapidly with desoxymethasone (often within 2 or 3 days) than with the comparison drug.

In almost all studies desoxymethasone has been applied in the commercially available form, a ‘slightly greasy’ water-in-oil emulsion base containing 0.25% of the drug, while apparently the comparison agent has usually been administered in the form of a standard ointment or cream, although in many studies the vehicle of the comparison drug was not described. Whether the apparent differences which have been observed in some studies between desoxymethasone and other similar fluorinated corticosteroids represent inherent differences in the drugs themselves, or arise from differing characteristics of the vehicles used, has not been considered by most authors. In a single study in which this was examined however, both drugs being administered in water-in-oil emulsion bases, 0.25% desoxymethasone and 0.1% triamcinolone acetonide were of similar efficacy in patients with eczema or dermatitis but desoxymethasone was superior in patients with psoriasis, as has occurred in other trials, suggesting that desoxymethasone is more potent than triamcinolone acetonide in the concentrations studied.

Side-effects: Although desoxymethasone has been well tolerated in most patients in published studies, as might be expected it can produce the adverse reactions associated with other topical corticosteroids. In short-term trials 0.24% of patients have discontinued treatment due to side-effects such as erythema, itching, scaling, increased weeping and exudation. Other reactions usually associated with longer-term use of topical corticosteroids, such as an acne-like rash, folliculitis, striae and hypertrichosis have occasionally been reported to have occurred during short-term use of desoxymethasone.

The tolerance rate during longer-term (up to 20 months) administration has been cited as 97.5%. A single case of florid Cushingoid manifestations has been reported following chronic excessive use of desoxymethasone (up to 30g of the commmercial preparation daily) over a 5-year period in a patient with psoriasis.

Administration: Desoxymethasone is available in a ‘slightly greasy’ water-in-oil emulsion base, containing 0.25% of the drug, which is claimed to be suitable for application to both dry and wet lesions. Initially it should be applied to the affected area 2 or 3 times daily and gently rubbed in if possible. When improvement occurs the frequency of application should be reduced. Although continued application after symptomatic improvement is claimed to prevent recurrence, continuous long term use of desoxymethasone can be expected to involve the same potential problems as may occur with other topical corticosteroids used in this way, and its use in this manner should be avoided whenever possible. As with other drugs of this type, occlusive dressings applied after drug application may increase the response (although this did not occur in a mixed group of patients with psoriasis, eczema or dermatitis in the only study which has examined this to date), but also increase the likelihood of adverse local and systemic effects. The possibility of significant systemic absorption should be particularly considered in infants and children.

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