Clinical Pharmacy - Skin Disorders

Skin

The body's largest organ.

Skin Functions

Protection against trauma, regulation of body temperature maintenance of water and electrolyte balance, sensing stimuli, vitamin D production, immune system.

Nerve receptors in the skin

Respond to touch, pressure (mechanoreceptors), temperature (thermoreceptors), and pain (nociceptors).

Stratum corneum

Outermost layer of the epidermis, maintains fluid loss.

Epidermis

Outermost layer of the skin.

Dermis

Middle layer of the skin.

Hypodermis

Deepest, fatty (adipose) layer of the skin.

Arrector pili muscle

Structure within the skin layers.

Hair follicle

Structure within the skin layers; produces hair.

Sebaceous gland

Structure within the skin layers; produces sebum.

Sweat gland

Structure within the skin layers; regulates body temperature.

Stratum corneum

Outermost layer of the epidermis; waterproof and prevents entry of substances.

Stratum basale

Innermost layer of the epidermis where keratinocytes originate.

Keratinocytes

Cells produced in the stratum basale that migrate towards the surface.

Melanocytes

Cells in the epidermis that produce melanin (pigment).

Melanin

Pigment produced by melanocytes; filters UV radiation.

Nerve endings in the dermis

Sense pain, touch, pressure, and temperature.

Sebum

Oily substance produced by sebaceous glands; keeps skin moist.

Vasodilation

Enlargement of blood vessels; occurs in response to heat.

Vasoconstriction

Narrowing of blood vessels; occurs in response to cold.

Hypodermis functions

Insulates the body, provides padding, and serves as an energy storage area.

Adipose tissue

Tissue in the hypodermis; stores fat.

Bursae

Small, fluid-filled sacs in the hypodermis; act as cushions and lubricants.

Percutaneous absorption

Absorption through the skin, primarily via intercellular or transcellular routes.

Passage through the stratum corneum.

Rate-limiting step in percutaneous absorption

Amphiphilic

Having adequate solubility in both oil and water; needed for topical drugs.

Partition coefficient

Drug should be able to partition from vehicle to stratum corneum for absorption.

Clinical endpoint

Used to determine effectiveness of a topical drug (e.g., resolution of symptoms).

TDDS

Transdermal Drug Delivery Systems; bypasses hepatic first-pass effect.

Advantage of TDDS

Less invasive than injections, easier for patients, painless, and bypasses first-pass metabolism.

Surface area to mass ratio in infants and children

Greater than adults, leading to greater systemic exposure to topical drugs.

Ointments

Best for dry skin.

Creams

Best for moist or weeping lesions.

Gels

Good for hairy areas.

Lotions

Good for wide areas of application and moisturizing.

Benzathine penicillin G (BPG)

Given intramuscularly for slow release and prolonged antibacterial effect.

Lidocaine

May be given with BPG for local anesthesia.

Insulin

Generally not suitable for topical administration due to large molecular size.

Adverse effect of topical corticosteroids

Prolonged use can cause adrenal insufficiency and Cushing's syndrome.

Skin disorder

Conditions affecting the skin, causing rashes, inflammation, itchiness, or other changes.

Psoriasis

Autoimmune disorder causing raised, scaly plaques.

Eczema

Related to immune system response; causes skin inflammation.

Acne vulgaris

Most common skin condition.

Propionibacterium acnes (Cutibacterium acnes)

Gram-positive, anaerobic bacteria; part of normal skin flora.

Hyperkeratinization

Impaired shedding of keratinocytes, leading to accumulation and comedones.

Comedones

Open (blackheads) or closed (whiteheads) clogged pores.

Graded from 1 to 4 based on severity.

Grades of Acne Vulgaris

Grade 1 Acne

Comedonal; only comedones (blackheads and whiteheads).

Grade 2 Acne

Mild Papular/Pustular; inflammatory papules and pustules present.

Grade 3 Acne

Moderate Pustular; more numerous and larger pustules, some nodules.

Grade 4 Acne

Severe Nodulocystic; many pustules, large, painful nodules and cysts.

Retinoids

Used to treat hyperkeratinization in acne.

Salicylic acid

Keratolytic agent; thins the skin and removes dead skin cells.

Clindamycin and erythromycin

Topical antibiotics used to treat microbial colonization in acne.

Tetracyclines

Systemic antibiotics used to treat microbial colonization in acne (e.g., doxycycline, minocycline).

Adverse effects of tetracyclines

Vestibular toxicity, hyperpigmentation, vaginal candidiasis.

Benzoyl peroxide (BPO)

Used to address both Gram-positive and Gram-negative bacteria in acne.

Blue light therapy

Can kill bacteria; used in acne treatment.

Hormonal therapies

Can reduce sebum production in acne treatment.

First Generation Retinoids

Non-selective binding to RARs (Retinoic Acid Receptors).

Tretinoin

All-trans-retinoic acid, Vitamin A acid.

Isotretinoin

Oral medication; highly teratogenic.

Third Generation Retinoids

Designed to optimize receptor-selective binding.

Tazarotene

Used for acne and psoriasis.

Adapalene

Used for acne treatment.

Psoriasis

Chronic, non-communicable inflammatory disease caused by immune system dysfunction.

Plaques

Raised, scaly areas on the skin due to inflammation in psoriasis.

Environmental triggers and genetic susceptibility

Factors that can contribute to the pathophysiology of psoriasis.

Pro-inflammatory cytokines in psoriasis

IL-23, IL-12, IL-17, IFN-gamma, TNF-alpha, IL-1.

Plaque Psoriasis (Psoriasis Vulgaris)

Most common type; raised, red plaques with silvery scales.

Erythrodermic Psoriasis

Severe type of psoriasis, covering a large area of the skin.

Guttate Psoriasis

Small, drop-shaped spots; often triggered by infection.

Inverse Psoriasis

Affects skin folds; presents as smooth, red lesions.

Pustular Psoriasis

Characterized by pus-filled blisters (pustules).

Scalp Psoriasis

Can range from fine scaling to thick, crusted plaques on the scalp.

Nail Psoriasis

Thickened, pitted, or ridged nails.

Stress, environmental factors, and infections

Triggers for psoriasis.

Red, scaly patches (plaques), itching, burning, or soreness, dry skin, thickened nails, joint pain.

Clinical presentation of psoriasis

Nails, elbows, knees, lower back, scalp, palms, soles, skin folds.

Common locations for psoriasis

Topical Corticosteroids

Anti-inflammatory, anti-proliferative, immunosuppressive, and vasoconstrictive effects.

Clobetasol propionate

Ultra-High potency topical corticosteroid.

Hydrocortisone

Low potency topical corticosteroid.

Tachyphylaxis

Reduced response with repeated use of topical corticosteroids.

Topical Calcineurin Inhibitors

Block calcineurin, inhibiting activation and synthesis of pro-inflammatory cytokines.

Tacrolimus

Topical calcineurin inhibitor, off-label use for psoriasis.

Topical Vitamin D Analogs

Bind to vitamin D receptors, inhibiting keratinocyte proliferation and enhancing differentiation.

Calcipotriol

Topical vitamin D analog.

Calcitriol

Topical vitamin D analog.

Tazarotene

Third-generation retinoid; normalizes keratinocyte differentiation.

Salicylic Acid

Topical keratolytic agent; reduces binding between keratinocytes.

Phototherapy (Light Therapy)

Uses ultraviolet (UV) light to slow down skin cell growth and reduce inflammation.

PUVA

Psoralen + UVA; combines UVA light with photosensitizing compounds.

Methoxalen

Psoralen used in PUVA therapy; can be taken orally or applied topically.

UVB (Ultraviolet B) therapy

Uses UVB light to treat psoriasis.

Conventional Systemic Agents (DMARDs)

Used for moderate to severe psoriasis (e.g., Methotrexate, Cyclosporine, Acitretin, Apremilast).

Biologic Therapies

Target specific immune system components in psoriasis treatment.

Adalimumab (Humira)

Biologic therapy for psoriasis.

Infliximab (Remicade)

Biologic therapy for psoriasis.

Secukinumab (Cosentyx)

Biologic therapy for psoriasis.

Ustekinumab (Stelara)

Biologic therapy for psoriasis.