Developments in topical retinoid therapy for acne

50 Years of Topical Retinoids for Acne: Evolution of Treatment

Since the US Food and Drug Administration (FDA) approved tretinoin in 1971, retinoids alone or combined with other agents have become the mainstay of acne treatment. Retinoids act through binding to retinoic acid receptors, altering expression levels of hundreds of cellular proteins affecting multiple pathways involved in acne pathogenesis. Retinoids have evolved from first-generation agents, such as tretinoin, through chemical modifications resulting in a second generation (etretinate and acitretin for psoriasis), a third generation (adapalene and tazarotene) and, most recently, a fourth (trifarotene). For all topical retinoids, local irritation has been associated with poor tolerability and suboptimal adherence. Efforts to improve tolerability have utilized novel delivery systems and/or novel agents. This qualitative literature review summarizes the evolution of the four topical single-agent retinoids available for the treatment of acne in the US today and their various formulations, presenting the rationale behind their development and data from key studies.

Short contact therapy of acne with tretinoin

The most frequent side effect of topical retinoids is irritant contact dermatitis. It occurs in approximately 85% of patients; the percentage can reach up to 95% in patients treated with tretinoin. Severity of this dermatitis is moderate to severe in approximately 20% of patients. However, 15% of patients stop the treatment with tretinoin because of skin irritation. The authors used tretinoin as short contact therapy (SCT) in mild to moderate acne, in order to try to reduce the incidence and severity of irritant contact dermatitis. They present the final results of a sponsor-free, pilot, open, multicenter study. Seventy-four patients were treated with 0.05% tretinoin cream. It was applied once daily for 30 min. Treatment duration ranged from 8 to 32 weeks (mean duration: 12 weeks). Acne severity and treatment efficacy were evaluated by means of the Global Acne Grading System. A significant clinical improvement (≥50% from baseline) was observed in 41 patients (55.4%). Thirteen patients (17.6%) developed a mild skin irritation. Four patients (5.4%) stopped the treatment because of severe skin irritation. Efficacy of tretinoin used as SCT seems to be superimposable to that of tretinoin used according to standard modality. Tolerability of SCT with tretinoin is very good. This tolerability allows a high adherence of patients to the treatment and it markedly improves compliance.

Cosmeceuticals vitamins

The term cosmeceutical was created over 25 years ago to define products with active substances that cannot be considered cosmetics or drugs. Cosmeceuticals are increasingly popular, with sales representing one of the largest growing segments of the skin care market. These products are found in many forms, including vitamins, peptides, growth factors, and botanical extracts. Cosmeceuticals that contain topically applied vitamins have an increasing role in skin care.

Physicians underutilize topical retinoids in the management of acne vulgaris: analysis of U.S. National Practice Data

BACKGROUND

Topical retinoids are effective in the treatment of acne, yet no current guidelines existed in the literature until recently recommending their use as an integral part of mild to moderate acne treatment.

OBJECTIVE

To assess whether underutilization of topical retinoids occurs in clinical practice.

DESIGN

Weighted data on representative office visits with acne vulgaris diagnoses were analyzed using the National Ambulatory Medical Care Survey (NAMCS), from 1990 to 1999.

RESULTS

Of the 54.2 million acne vulgaris visits, retinoids were prescribed at 35.3% visits. Dermatologists prescribed significantly more retinoids than non-dermatologists (39.4%' versus 23%). Dermatology visit was a significant predictor of topical retinoid prescription (RR: 2.27,95% CI: 1.63-3.17). Data suggest that prescribing retinoids for acne has been increasing over the past decade, primarily among dermatologists.

CONCLUSION

There is a major difference between suggested treatment guidelines for acne and actual practice in the community. There is distinct under-utilization of topical retinoids for treatment of acne vulgaris by dermatologists and non-dermatologists.

‘Keratolytic’ Properties of Benzoyl Peroxide and Retinoic Acid Resemble Salicylic Acid in Man

OBJECTIVES

Retinoic acid (RA) and benzoyl peroxide (BP) were studied, comparing their keratolytic efficacy and water barrier disruption to that of salicylic acid (SA), a well-established keratolytic, under similar conditions.

PATIENTS/METHODS

Six volunteers were included in this blinded study. Eleven randomized test sites were marked on the volar forearms, containing sites for untreated skin at time zero, unoccluded, occlusion, and vehicle controls for 3 and 6 h, and each of BP, RA, and SA solutions for 3 and 6 h. At each time point, occlusion at 5 of the test sites was removed, and chromameter measurements were performed over 30 min. Each site then underwent 25 stratum corneum (SC) tape strippings. At 1, 5, and 30 min after the last stripping at each site, TEWL measurements were performed. Quantitative protein analysis of the SC from the tapes was then performed.

RESULTS AND CONCLUSION

after 3 h, bp was significantly more effective in disrupting sc cohesion than sa and ra, indicating bp is a moderate keratolytic agent in addition to its antimicrobial properties. After 6 h, all three agents were similarly effective in keratolysis. Barrier disruption, as measured by TEWL, paralleled depth of SC removal. SA tended to exhibit the greatest keratolytic efficacy superficially, hence its clinical effectiveness in superficial conditions such as comedonal acne, whereas BP was more effective at deeper levels, complimenting its antimicrobial effects and enabling it to treat deeper, more inflammatory lesions. None of the agents significantly affected skin erythema. These techniques provide a robust and rapid assay for in vivo keratolytic demonstration.

Acne: Topical treatment

Acne vulgaris is a common skin disease, affecting about 70-80% of adolescents and young adults. It is a multifactorial disease of the pilosebaceous unit.(1) The influence of androgens at the onset of adolescence leads to an enlargement of the sebaceous gland and a rise in sebum production. Additional increased proliferation and altered differentiation of the follicular epithelium eventually blocks the pilosebaceous duct, leading to development of the microcomedo as the primary acne lesion. Concomitantly and subsequently, colonization with Propionibacterium acnes increases, followed by induction of inflammatory reactions from bacteria, ductal corneocytes, and sebaceous proinflammatory agents (Fig 1).(2-5)

Topical acne drugs: review of clinical properties, systemic exposure, and safety

This review examines the commonly available topical acne agents and factors that determine their percutaneous absorption. Reported and theoretical adverse effects from systemic exposure are detailed. The topical retinoid class, which includes tretinoin, adapalene and tazarotene, and the topical antibacterials, clindamycin and erythromycin, are regulated by prescription in most countries. Used appropriately, the above-mentioned drugs deliver, at most, miniscule amounts of active ingredient into the circulation. Clear-cut links to systemic toxicity in humans are practically nonexistent, except in the case of topical clindamycin, which has been associated with diarrhea rarely, and there have been 2 cases of pseudomembranous colitis reported. Birth defects have occurred in two patients treated with tretinoin and one patient treated with adapalene, but causation was not proven. Another prescription drug, 20% azelaic acid, is associated with relatively high systemic exposure, which is presumed innocuous because it is a normal dietary constituent whose endogenous levels are not altered by topical use. Benzoyl peroxide, salicylic acid, sulfur, and sodium sulfacetamide are available in concentrations of 2% or more in over-the-counter acne treatments and some prescription products. All of these agents are known to exhibit some degree of percutaneous absorption. They remain largely unregulated because, other than skin irritation, only local allergic contact dermatitis from benzoyl peroxide in about 2.5% of patients and rare local and systemic hypersensitivity reactions from sodium sulfacetamide have been reported. Salicylism has occurred using methyl salicylate ointments and high concentrations of salicylic acid on widespread areas of hyperkeratotic skin, but there are no known cases resulting from salicylic acid acne products. Caution is advised in special circumstances, such as during childhood, pregnancy, lactation and concomitant therapy with other drugs, because relevant studies are lacking. Animal data support avoidance of many topical agents, particularly known teratogens such as retinoids and salicylic acid, in pregnant women. Salicylate avoidance is advised during lactation, because aspirin use carries the risk of bleeding disorders in nursing infants.

Changing paradigms in dermatology: nuclear hormone receptors

Nuclear hormone receptors (NHRs) are a family of proteins that function similarly as nuclear transcription factors. The NHR family includes glucocorticoid receptors, retinoic acid and retinoid receptors, vitamin D receptors, thyroxin receptors, and peroxisome proliferator activated receptors. These proteins are targets for some of the most commonly prescribed medications in dermatology, including corticosteroids, retinoids, and vitamin D analogues, all of which have limiting side effects. Advances in this field have led to better understanding of the mechanisms of NHR therapeutic and toxic effects, receptor subtypes, tissue distribution, and interaction with other molecules. New generations of more specific NHR ligands designed to increase therapeutic efficacy and limit adverse effects have dramatically expanded the clinical application of NHR-targeting drugs. The current understanding of NHRs and future directions for NHR ligands in dermatology are discussed.

Transglutaminases: nature's biological glues

Transglutaminases (Tgases) are a widely distributed group of enzymes that catalyse the post-translational modification of proteins by the formation of isopeptide bonds. This occurs either through protein cross-linking via epsilon-(gamma-glutamyl)lysine bonds or through incorporation of primary amines at selected peptide-bound glutamine residues. The cross-linked products, often of high molecular mass, are highly resistant to mechanical challenge and proteolytic degradation, and their accumulation is found in a number of tissues and processes where such properties are important, including skin, hair, blood clotting and wound healing. However, deregulation of enzyme activity generally associated with major disruptions in cellular homoeostatic mechanisms has resulted in these enzymes contributing to a number of human diseases, including chronic neurodegeneration, neoplastic diseases, autoimmune diseases, diseases involving progressive tissue fibrosis and diseases related to the epidermis of the skin. In the present review we detail the structural and regulatory features important in mammalian Tgases, with particular focus on the ubiquitous type 2 tissue enzyme. Physiological roles and substrates are discussed with a view to increasing and understanding the pathogenesis of the diseases associated with transglutaminases. Moreover the ability of these enzymes to modify proteins and act as biological glues has not gone unnoticed by the commercial sector. As a consequence, we have included some of the present and future biotechnological applications of this increasingly important group of enzymes.