D: Dermatologicals

ATC group D for modelers: bounded skin severity scores and site-of-action exposure sampled or predicted, with D05, D07 and D11 notes on their own pages.
Modified

September 22, 2026

Drugs applied to the skin, and, in D11, antibodies and an oral kinase inhibitor for atopic dermatitis that are given systemically [1]. For the topical majority the target tissue is also the site of administration, so plasma reports systemic safety rather than the driver of effect.

In 1962 A. W. McKenzie and R. B. Stoughton published a method for comparing the percutaneous absorption of steroids [2]. The skin blanching assay that grew from it is still called the Stoughton-McKenzie assay [3], and the FDA accepts it as a surrogate for the bioequivalence of topical glucocorticoids [4].

Table 1: ATC D level 2 codes
Level 2 code Description In plain terms Example drug
D01 Antifungals for dermatological use Terbinafine, topical (D01AE15) / terbinafine, oral (D01BA02)
D02 Emollients and protectives moisturisers and barrier creams Carbamide, i.e. urea (D02AE01). Most emollient bases carry no level 5 substance code: D02AC (soft paraffin and fat products) is group-level only.
D03 Preparations for treatment of wounds and ulcers Cadexomer iodine (D03AX01) / collagenase (D03BA02). Both are adjuncts: wound and ulcer care is led by dressings, offloading and debridement rather than by a drug-level standard.
D04 Antipruritics, incl. antihistamines, anesthetics, etc. anti-itch creams and numbing agents Lidocaine (D04AB01) / doxepin (D04AX01)
D05 Antipsoriatics Calcipotriol, combinations, i.e. with betamethasone (D05AX52) / acitretin (D05BB02)
D06 Antibiotics and chemotherapeutics for dermatological use topical antibacterials and antivirals, not anticancer Mupirocin (D06AX09) / imiquimod (D06BB10)
D07 Corticosteroids, dermatological preparations Mometasone (D07AC13) / hydrocortisone (D07AA02)
D08 Antiseptics and disinfectants Chlorhexidine (D08AC02) / povidone-iodine (D08AG02)
D09 Medicated dressings bandages impregnated with a drug Povidone-iodine dressings (D09AA09) / chlorhexidine dressings (D09AA12). Modern silver, foam and hydrocolloid dressings have no level 5 code; D09AX (soft paraffin dressings) is group-level only.
D10 Anti-acne preparations Adapalene (D10AD03) / isotretinoin, oral (D10BA01)
D11 Other dermatological preparations Tacrolimus, topical (D11AH01) / dupilumab (D11AH05)

Modeling notes

Endpoint. Bounded composite severity scores: PASI in psoriasis [5] and EASI in atopic dermatitis [6].

Site-of-action exposure is sampled directly or not at all. Dermal open flow microperfusion measures dermal concentrations in vivo, and separated bioequivalent from non-bioequivalent lidocaine and prilocaine products on dermal AUC and Cmax [7].

Easy to overlook. The D11 biologics are an ordinary systemic PKPD problem: nemolizumab exposure fell as bodyweight rose, yet simulated EASI, pruritus and IGA response rates were similar above and below 90 kg [8].

Mechanistic extrapolation. Dermal PBPK ties formulation and skin physiology to systemic kinetics [9], and contributed to an FDA generic approval of topical diclofenac gel within a totality of evidence [10].

References

[1]
WHO Collaborating Centre for Drug Statistics Methodology. ATC/DDD index 2026 2026.
[2]
McKenzie AW, Stoughton RB. Method for comparing percutaneous absorption of steroids. Archives of Dermatology 1962;86:608–10. https://doi.org/10.1001/archderm.1962.01590110044005.
[3]
Herkenne C, Alberti I, Naik A, Kalia YN, Mathy F-X, Préat V, et al. In vivo methods for the assessment of topical drug bioavailability. Pharmaceutical Research 2008;25:87–103. https://doi.org/10.1007/s11095-007-9429-7.
[4]
Alomari N, Alhussaini W. Update on the advances and challenges in bioequivalence testing methods for complex topical generic products. Frontiers in Pharmacology 2024;15. https://doi.org/10.3389/fphar.2024.1330712.
[5]
Ooi QX, Kristoffersson A, Korell J, Flack M, L. Plan E, Weber B. Bounded integer model‐based analysis of psoriasis area and severity index in patients with moderate‐to‐severe plaque psoriasis receiving BI 730357. CPT: Pharmacometrics & Systems Pharmacology 2023;12:758–69. https://doi.org/10.1002/psp4.12948.
[6]
Okada H, Liao S, Khouri L, Liao L, Hruska MW, Nagata Y, et al. Continuous‐time markov population PK/PD modeling of longitudinal EASI categorical score in atopic dermatitis treated with rocatinlimab, an anti‐OX40 monoclonal antibody. CPT: Pharmacometrics & Systems Pharmacology 2025;14:1587–97. https://doi.org/10.1002/psp4.70069.
[7]
Tiffner KI, Ramezanli T, Boulgaropoulos B, Birngruber T, Bodenlenz M, Lackner BC, et al. Cutaneous pharmacokinetics-based bioequivalence: A clinical dermal open flow microperfusion verification study using lidocaine and prilocaine combination topical products. European Journal of Pharmaceutical Sciences 2024;200:106827. https://doi.org/10.1016/j.ejps.2024.106827.
[8]
Fauchet F, Largajolli A, Jauslin PM, Schindler E, Hamimed M, Kantasiripitak W, et al. Model‐informed drug development to support nemolizumab clinical development in adults and adolescents with moderate to severe atopic dermatitis. British Journal of Clinical Pharmacology 2026;92:1744–59. https://doi.org/10.1002/bcp.70435.
[9]
Shah H, Banerjee A, Damre A. Dermal PBPK modeling in the era of model-informed drug development: Strategies, innovations, and regulatory impact. Drug Discovery Today 2026;31:104705. https://doi.org/10.1016/j.drudis.2026.104705.
[10]
Tsakalozou E, Babiskin A, Zhao L. Physiologically-based pharmacokinetic modeling to support bioequivalence and approval of generic products: A case for diclofenac sodium topical gel, 1%. CPT: Pharmacometrics & Systems Pharmacology 2021;10:399–411. https://doi.org/10.1002/psp4.12600.