Acne vulgaris is a highly prevalent dermatologic disorder in industrialized societies and affects approximately 85% of individuals between the ages of 12 and 24 years.1 In the United States, more than 50 million people are estimated to be dealing with some form of the disease,1 including approximately 15.7 million adolescents between ages 12 to 17.2
Acne is a multifactorial inflammatory disorder. The pathophysiology involves four factors, including excess sebum production secondary to hormonal changes of puberty, abnormal desquamation of follicular keratinocytes, proliferation of Propionibacterium acnes within the follicle, and inflammation and immune responses caused by the production of pro-inflammatory molecules, including chemo-attractants released by P. acnes.3 Treatment goals include resolving symptoms, preventing the development of new lesions and scarring, and treating postinflammatory hyperpigmentation.
Current acne treatments target one or more of the known mechanisms involved in the disease; however, two additional issues require consideration. One is the role of the vehicle. Selection of a vehicle that minimizes irritation and other skin reactions is crucial to the success of the treatment regimen and may be as important as the active ingredient selected.
The second issue is the increasing incidence of bacterial resistance. Antimicrobial therapy, one of the mainstays of acne treatment, has been complicated by the emergence of antibiotic-resistant strains of P. acnes. Antibiotic-resistant strains of P. acnes have increased steadily over the past three decades and are now found in more than 50% of cases in Europe and the United Kingdom.4 Resistant strains of P. acnes are associated with treatment failure.5
This article focuses on these key challenges, strong factors in determining treatment success. Practitioners considering these factors as important in their selection of topical acne treatments may find their patients more compliant and outcomes more successful.
Role of the vehicle
Topical medications are widely used in dermatology and exhibit activity largely where and when they are applied. Available in cream, gel, lotion, or solution form, they treat existing lesions and prevent new outbreaks. Hence, they require application on a daily or twice daily basis to all skin areas prone to acne. The most frequent side effect of topical acne products is skin irritation, and combination agents can increase the risk of a skin reaction. Skin irritation and reactions with poor medication tolerance will limit medication usefulness, decrease compliance, and may lead to discontinuation of therapy.6 Minimizing these types of reactions is essential to maintaining acne therapy. Therefore, the goal becomes identification of the most effective regimen that is well tolerated and will fit into the patient’s schedule.
Epidermal barrier in acne
Normal, healthy skin prevents transepidermal water loss (TEWL) and protects the underlying tissues from toxins and irritants through the interplay of various elements collectively known as the epidermal barrier. Acne vulgaris disrupts the epidermal barrier in a number of ways. When the epidermal barrier is impaired due to inflammation, infection, and irritation6 from topical medications, TEWL occurs, and there is an increased potential for exposure to infection and environmental irritants.6
The epidermal barrier may be disrupted by multiple mechanisms, including the underlying acne disorder and the application of topical treatments used for acne.3
The epidermal barrier can be restored by many mechanisms. Two important mechanisms for rehydrating the stratum corneum are to attract water from viable skin layers to the stratum corneum through the use of humectants and to trap moisture via the use of emollient occlusives.3 Vehicle formulations that limit skin irritation to minimize barrier impairment and assist in restoring barrier function are valuable components of acne therapy, especially early in the course of treatment and with combination regimens.