G.P. Raymond, MD, FRCPC, DABD; M.-C. Houle, MD
Dermatology Service, Centre Hospitalier Université de Montréal, Montréal, QC, Canada
The Different Potencies
One of the most influential developments in the treatment of psoriasis and other inflammatory skin diseases occurred in the 1950s with the introduction of topical hydrocortisone.
- The further addition of side chains and halogenation increased the potency of topical corticosteroids.
- This in turn further increased the treatment options for psoriasis.
These compounds can be classified in different groups depending on their potency. See Table 1.
|I||Super-high potency||Clobetasol propionate|
|II||Super potent||Betamethasone dipropionate (optimized vehicle)|
|IV||Potent||Betamethasone dipropionate (regular vehicle)|
|V||Medium potency||Betamethasone valerate|
|Table 1: Some commonly used topical corticosteroids ranked by potency into 7 different classes.|
The Importance of the Vehicle
Prior to the mid-1970s, the vehicle of a topical medication was not believed to have any impact on the potency and effectiveness of a given formulation.
- When a new molecule was tested, different concentrations were randomly mixed with various preparations and then applied in a variety of quantities in order to observe the effect on diseased skin.
- More controlled research has allowed researchers to determine that the penetration of a given corticosteroid could be greatly improved with the addition of:
- propylene glycol
- salicylic acid
- Since then, many more compounds have been formulated with different bases in order to increase their efficacy.
- The vehicle is not only what brings a drug in contact with the skin, but is the link between drug potency and therapeutic effectiveness.
- It is a highly engineered balance of numerous chemicals. Each serves a separate or overlapping purpose in order to achieve the characteristics of an effective vehicle:
- Chemically and physically stable
- Does not inactivate the drug
- Nonirritating, hypoallergenic
- Cosmetically acceptable
- Easy to use
- Allow the proper release of the drug.
- The same corticosteroid molecule may rank in different classes when formulated in different vehicles, e.g., betamethasone dipropionate prescribed as diprolene ointment .05% and diprosone ointment .05% are categorized in class II and IV, respectively.
- In general, compounds that contain a higher amount of propylene glycol are more potent.
- As a general rule of thumb, ointments tend to be more potent than creams and lotions.
- It is important to remember that creams, gels, solutions, lotions can also be specifically formulated to be almost equipotent to ointments in some cases.
- The vehicle often has beneficial nonspecific effects by possessing cooling, protective, emollient, occlusive, or astringent properties.
- These effects should not be overlooked. In the end, it is the general acceptability and efficacy of a preparation that will result in patient’s compliance.
Generic vs. Brand-name Products
- No comparative labeling exists to ensure equal efficacy between generic and brand name products.
- The potency of generic products is not always equivalent to the brand name preparation and vice versa.
- Variability exists between the different generic preparations, emphasizing the effect of vehicle on a preparation’s potency.
Proper Use of Steroids for Various Skin Conditions
Since their introduction, topical corticosteroids have become a mainstay in the treatment of many skin diseases such as psoriasis. But to properly use topical corticosteroids, the physician must first choose the desired potency based on:
- A patient’s age:
- Children have a higher ratio of skin surface area to body weight and are less able to metabolize potent glucocorticoids rapidly.
- Very mild corticosteroids should be prescribed to young children, especially in the diaper area and in the folds.
- Elderly patients have thinner skin and thus strong corticosteroids should be used with caution.
- The disease type:
- Atopic dermatitis, diaper dermatitis, nummular dermatitis, intertriginous psoriasis and seborrheic dermatitis are all conditions typically very sensitive to topical corticosteroids.
- Mid to mild potency should be used.
- The location:
- Penetration through the eyelids and scrotum is 4 times greater than for the forehead and 36 times greater than for the palms and soles.
- Occluded areas such as flexures, axillae, and the groin area absorb corticosteroids more rapidly; mild preparations should be used.
- In general, halogenated corticosteroids (i.e., Class 1–5 except hydrocortisone-17-valerate) should not be used on the face, and in the skin folds.
- Topical corticosteroids are better absorbed on moist skin.
- The severity and extent of the lesions
- Pregnancy (Most corticosteroids are Category C.) Topical corticosteroids should be applied sparingly and rubbed into the affected area. A rule of thumb for the quantity of cream or ointment to use is a pea-sized amount for a 5cm x 5cm area of skin.
Adverse effects of topical corticosteroids increase with the potency of the preparation. Physicians and pharmacists must be aware of the most frequent adverse side-effects of topical corticosteroids such as:
- stinging and burning upon application
- epidermal atrophy and dermal atrophy (usually after several weeks of use)
- perioral dermatitis, steroid-induced rosacea, steroid acne
- suppression of the pituitary-adrenal axis (especially with the potent ones)
- purpura/ easy bruising
- Tachyphylaxis (decreased effect of the drug)
- It can occur as early as after 1 week, but generally takes several weeks to a month to occur.
- Stopping treatment for 4–7 days, and then reinstating treatment thereafter has been shown to be beneficial in stopping tachyphylaxis.
It is also important, as with most other prescription drugs, to ensure a patient is under proper medical supervision. A patient’s follow-up visit with his physician will optimize benefits and minimize adverse effects of a topical corticosteroid treatment. Physicians and pharmacists alike should be aware of the importance and the difference of various vehicles when prescribing topical corticosteroids.