A24. Local therapy in dermatology

  • Unilateral treatment allows for easier treatment response evaluation than with systemic treatment
  • Topical preparations/formulations consist of a drug in a non-active base/vehicle
  • Drugs used on skin must be dissolved or suspended in a vehicle
    • The choice of drug depends on the diagnosis
    • The choice of vehicle depends on the state of the skin
    • The drug will be transferred from the vehicle to stratum corneum
    • The base determines the rate at which the drug is absorbed through the skin
  • An overview of different types of topical formulations. From https://plasticsurgerykey.com/other-topical-medications-2/
    Vehicles
    • Liquid vehicles
      • Water
      • Ethanol
      • Glycerol
    • Solid vehicles (powders)
      • Zinc oxide
      • Titanium oxide
      • Talc
      • Starch
    • Fatty vehicles (greases)
      • Vegetable fats
      • Animal fats
      • Mineral oils
      • Petrolatum
  • Types of topical preparations
  • Topical preparations
    • Solution
      • Drug dissolved in a liquid solvent like alcohol or water
      • Convenient to apply (can be applied with a dropper)
    • Lotions
      • Water-based emulsion
      • Thicker than solution
      • Good for hairy skin
      • They cool inflammatory lesions and dry exudative lesions
    • Creams
      • A semisolid emulsion of water in oil or oil in water
      • Thicker than lotion
      • Good for weeping lesions
      • When applied with wet compress -> good for inflamed skin
    • Ointments
      • Semisolid grease or oil, without water
      • Good for scaly or dry lesions
      • When applied with wet compress -> good for inflamed skin
    • Gels
      • Soft, semisolid preparation
      • Liquefy on contact with the skin
    • Foam
      • Aerosolized solution with a pressurized propellant
      • Good for hairy skin
    • Powders
      • Solid
      • For lesions in moist or intertriginous areas
    • Cooling paste
      • Contains oil, water and powder
      • Often contains zinc oxide
      • Cools inflamed skin
  • Dressings
    • Protect open lesions, facilitate healing, increase drug absorption
    • Non-occlusive dressings (wet dressings)
      • Dressings wetted with saline or water
      • Applied to the lesion and removed when the solution has evaporated
      • Good for thick or crusted lesions
      • Good for oozing lesions
    • Occlusive dressings
      • Increase the absorption and effectiveness of topical therapy
      • Can be applied over topical preparations to increase absorption
      • Can be applied to open wounds to allow them to heal
  • Moisturizing agents (emollients)
    • Restore water and oil to skin and help maintain skin hydration
    • More effective in slightly wet skin, like after a shower
    • Available as lotions, creams, ointments, etc.
    • Indicated in dry skin conditions
    • Contains occlusives and humectants
    • Humectants
      • These agents attract water, increasing the water-holding capacity of the stratum corneum
      • Glycerine
      • Urea
      • Lactic acid
      • Glycolic acid
    • Occlusives
      • Form a physical barrier to prevent water loss
      • Waxes
      • Petrolatum
      • Oils
  • Drying agents (powders)
    • To treat excessive moisture, like between skin folds, the groin, etc
    • Corn starch
    • Talc
  • Topical agents to alleviate pruritus
    • Pramoxine
    • Hydrocortisone
    • Menthol
    • Phenol
  • Keratolytics
    • These agents facilitate exfoliation of epidermal cells
    • Used to treat hyperkeratotic diseases like
      • Psoriasis
      • Seborrheic dermatitis
      • Acne
    • Urea
    • Salicylic acid
    • Lactic acid
    • Glycolic acid
  • Steroids
    • Widely used in dermatology
    • Indications
      • Cutaneous lupus erythematosus
      • Psoriasis
      • Lichen
      • Contact dermatitis
      • Atopic dermatitis
      • Allergic skin reactions
    • Mostly used steroids
      • Hydrocortisone (low potency)
      • Triamcinolone (medium potency)
      • Clobetasol (high potency)
    • Side effects
      • Skin atrophy
      • “Steroid acne”
      • Striae
      • Contact allergy
      • “Steroid rosacea” = perioral dermatitis
        • When potent steroids are used on the face
        • Telangiectasias
        • Papules, pustules
  • Topical antibiotics
    • Mostly used in acne
    • Tetracyclines
    • Metronidazole
    • Erythromycin
    • Clindamycin
    • Bacitracin
  • Silver nitrate
    • Low concentration – debride wounds
    • High concentration – cauterizes bleedings in wounds
  • Imiquimod
    • Immune regulator
    • Indications
      • Warts
      • BCC
      • Actinic keratosis
  • Topical calcineurin inhibitors
    • Tacrolimus
    • Pimecrolimus
    • Indications
      • Atopic dermatitis
  • 5-fluorouracil
    • Indications
      • Actinic keratosis
      • BCC
      • Warts
  • Fingertip units (FTU)
    • 1 FTU = the amount of topical preparation expressed from a tube when applied from the distal skin-crease to the tip of the index finger
    • 1 FTU is approx. 0,5 g
    • 1 FTU covers approx. 300 cm2, which is enough for one hand
    • 2,5 FTU covers the face and neck
    • Fingertip units are useful when telling patients how much they should use of a preparation