Page 88 - Retail Pharmacy November/Decemeber 2020

Table 2. Cascade of acne development. Adapalene is also anti-inflammatory. It inhibits lipoxygenase and oxidative metabolism of arachidonic acid, but animal studies indicate that the anti-inflammatory effect of adapalene is concentration dependent, suggesting that 0.3% has a greater anti-inflammatory effect than 0.1% adapalene.5 Therefore, adapalene improves acne via dual mechanisms. It reduces the formation of the corneocyte plug, which is the beginning of the comedone development cascade (anti-comedogenic) and reduces the inflammation caused by C. acnes overgrowth in and around the follicle. Adapalene has similar efficacy to tretinoin, with the advantage of being more chemically stable. Unlike tretinoin, adapalene stability is not affected by light or the presence of benzoyl peroxide, which makes it ideal for combination formulations. Due to its high lipophilicity, penetration of adapalene across the epidermis is low and so most of the applied dose is retained within the follicle and the epidermis. Ongoing research involves optimising the drug vehicle to maximise adapalene concentration within the epidermis where the pilosebaceous unit sits. Systemic absorption of topical adapalene is practically negligible.5 When to use adapalene In general, evidence and guidelines support the use of topical retinoids as first line therapy for the treatment of mild-moderate acne. This is supported by the American Academy of Dermatology, the European Dermatology Forum and the Global Alliance on Improving Outcomes in Acne.6,7 This is due to the dual mechanism of retinoids (both anti- comedogenic and anti-inflammatory). Therefore, topical retinoids can reduce already visible lesions and prevent new comedones from developing. There is further benefit in combining the topical retinoid with a topical antimicrobial agent (eg, benzoyl peroxide).6 The efficacy of all topical retinoids is concentration dependent and improves TO PAGE 88 CPD ACTIVITY 87 1. Skin cell proliferation • Corneocytes proliferate at the skin surface and down into the entrance to the duct of the pilosebaceous unit (pore). • Corneocytes resist shedding, accumulate, fall into and ‘plug’ the duct. • A blocked pore or comedone develops. 2. Sebum accumulation • Sebum production increases (under the influence of androgens), accumulates and cannot escape due to the blocked pore. • The follicle begins to dilate. 3. Proliferation of bacteria • Sebum continues to accumulate and dilate the follicle. Bacteria proliferate (C. acnes). • C. acnes stimulates the production of pro-inflammatory cytokines such as interleukin and tumour necrosis factor. • Intra-follicular inflammation leads to formation of a papule or pustule. 4. Follicular rupture • Dilation of the follicle causes it to rupture. Its contents, including sebum and C. acnes, spread to surrounding tissue. • This elicits an extra-follicular inflammatory response leading to nodule or cyst formation. • Inflammation can cause scarring. Table 3. Overview of acne treatment (modified from Therapeutic Guidelines).3 Mild acne • Primarily managed with topical treatment. • OTC treatments including salicylic acid and benzoyl peroxide 2.5-5%. • Add or change to topical adapalene 0.1%. • Or refer to a doctor for topical tretinoin (start at 0.025% and ↑ slowly). • If still inadequate: • For mainly comedonal acne: benzoyl peroxide 2.5% + adapalene 0.1%. • For comedonal and inflammatory acne: benzoyl peroxide 2.5% + adapalene 0.1% + refer to a doctor for topical antibiotic. Moderate acne • May require addition of oral treatment. • Topical adapalene 0.1% (or refer to a doctor for tretinoin 0.025-0.1%) +/- benzoyl peroxide 2.5%. • Or refer to a doctor for topical adapalene 0.3% + benzoyl peroxide 2.5%. • And refer to a doctor for oral antibiotics for males and combined oral contraceptive for females (+/- spironolactone, +/- oral antibiotics). Severe acne • Refer to a dermatologist for oral isotretinoin. use of oral isotretinoin for severe acne. However, the area in which pharmacists can make the greatest difference is management of mild-moderate acne. Control of mild acne is important as the aim of therapy is to prevent the development of moderate and then severe acne, when scars are more likely to form. The primary care role of pharmacists is to identify and treat mild-moderate acne and refer patients with moderate-severe acne to a doctor for assessment. The rescheduling of topical adapalene 0.1% to S3 gives pharmacists an additional tool for the treatment of mild-moderate acne. Table 3 represents a broad overview of acne treatment based on the Therapeutic Guidelines. This is a guide only and therefore local approaches to acne management and prescribing habits may differ. Adapalene Adapalene is a third-generation retinoid. It’s a lipophilic synthetic naphthoic acid derivative that penetrates quickly into the follicle of the pilosebaceous unit where it’s locally absorbed into cells. Once inside the cell, adapalene selectively binds specific forms of the retinoic acid receptor (RAR). The adapalene-RAR complex then binds to DNA and induces gene transcription, which affects downstream keratinocyte proliferation and differentiation. This results in decreased development of new comedones and exfoliation of mature comedones.4 JOIN TODAY TO ENJOY THESE MEMBER BENEFITS • CPD guarantee – four new topics each month • Learning plan and CPD credits summary transcript • Comprehensive and non-biased clinical education modules with online assessment questions LEARN MORE www.acp.edu.au info@acp.edu.au RETAIL PHARMACY • NOV/DEC 2020