Comprehensive Guide to Topical Corticosteroids in Clinical Pharmacy

Overview of Topical Corticosteroids

• Definition: Topical corticosteroids are anti-inflammatory agents applied directly to the skin to reduce inflammation and itching.

• Usage Context: They represent one of the oldest and most effective treatments for various dermatologic conditions, though they must be prescribed with consideration of diagnosis, potency, delivery vehicle, administration frequency, duration, and side effects.

• Core Mechanism: The efficacy and side effects of these drugs are a direct result of their anti-inflammatory properties. They function partially by causing vasoconstriction (narrowing of blood vessels) in the skin, which reduces redness and inflammation.

• Evidence-Based Specificity: While commonly used, scientific evidence of effectiveness is confirmed for specific conditions such as:

  • Psoriasis

  • Eczema

  • Atopic dermatitis

  • Acute radiation dermatitis

Choosing Topical Corticosteroids

• Prescriber Challenges: Clinicians unfamiliar with these agents face challenges due to the vast array of types, strengths, generic vs. brand name formulations, and diverse methods of application.

• Success Factors: Successful treatment relies on an accurate diagnosis and careful selection of the following:

  • Steroid potency (strength).

  • Steroid delivery vehicle (formulation).

  • Frequency of application.

  • Duration of treatment.

  • Potential side effects.

Potency Classification and Treatable Conditions

Topical steroid preparations are categorized based on their potency, which is determined by the degree of vasoconstriction they produce and their ability to inhibit inflammation.

1. High-Potency Steroids (Groups I to III)

• Indications:

  • Alopecia areata

  • Resistant atopic dermatitis

  • Discoid lupus

  • Hyperkeratotic eczema

  • Lichen planus

  • Lichen sclerosus (skin)

  • Lichen simplex chronicus

  • Nummular eczema

  • Severe poison ivy

  • Psoriasis

  • Severe hand eczema

2. Medium-Potency Steroids (Groups IV and V)

• Indications:

  • Severe anal inflammation

  • Asteatotic eczema

  • Atopic dermatitis

  • Lichen sclerosus (vulva)

  • Nummular eczema

  • Scabies (post-scabicide treatment)

  • Seborrheic dermatitis

  • Severe dermatitis

  • Severe intertrigo (short-term)

  • Stasis dermatitis

3. Low-Potency Steroids (Groups VI and VII)

• Indications:

  • Diaper dermatitis

  • Eyelid dermatitis

  • Face dermatitis

  • Intertrigo

  • Perianal inflammation

Vehicles and Formulations

Vehicles are designed to provide rapid drug delivery to the stratum corneum and deeper skin layers while being easy to apply and cosmetically acceptable.

• Potency Hierarchy: For the same corticosteroid, the potency generally follows: Ointment > Cream > Lotion.

• Ointments:

  • Most potent formulation due to their occlusive effect, which prevents water evaporation and increases absorption.

  • Greasy and sticky; typically unsuitable for large surface areas or hair-bearing areas.

• Creams:

  • Cosmetically appealing and water-washable.

  • Stronger than lotions but less potent than ointments.

• Lotions, Foams, and Solutions:

  • Highly effective for hairy areas (e.g., scalp) and large body areas.

  • Provide a cooling and drying effect as they evaporate, making them useful for moist dermatoses or pruritus (itching).

• Gels:

  • Transparent, colorless, semisolid emulsions that liquefy on contact with skin.

  • Efficiently deliver corticosteroids to hair-bearing areas and leave no greasy residue.

Regional Vehicle Preferences

• Dry and Thick Skin / Palms and Soles: Ointment is preferred.

• Scalp / Hairy Areas: Solution, Foam, or Gel is preferred.

• Skin Folds (Intertriginous areas): Cream is preferred. Ointments should be avoided in moist folds as they are too greasy.

• Infected Areas: Lotion or Solution is preferred.

Selection and Administration Guidelines

• General Rule: Start with the lowest potency agent necessary and use it for the shortest duration possible.

• Site-Specific Rules:

  • Eyelid and Genitals: Use only low-potency steroids for limited time periods due to high skin permeability.

  • Palms and Soles: Require super high-potency steroids because the thick stratum corneum resists drug penetration.

  • Face and Intertriginous Areas: Avoid super high-potency steroids; use low-to-medium strength instead.

• Surface Area Considerations: Use low-to-medium strength when treating large areas to minimize systemic absorption.

• Combination Therapy: Use corticosteroids in conjunction with moisturizers. Moisturizers help the skin heal and reduce dryness; the steroid should be applied first, followed by the moisturizer.

Frequency and Duration of Treatment

• Frequency: Once or twice daily. More frequent application does not improve results and increases the risk of side effects.

• Long-term Use:

  • Steroids must be gradually tapered to avoid rebound symptoms (the condition returning worse than before).

  • A steroid-free period of at least one week should occur before resuming treatment.

• Duration Limits:

  • Ultra-high potency steroids should not be used for more than $3 \, \text{weeks}$.

  • Low-to-high potency steroids should generally not exceed $3 \, \text{months}$ of continuous use.

Percutaneous Absorption Factors

Several factors influence how much of the drug is absorbed through the skin into the bloodstream:

1. Integrity of skin barrier: Damaged or inflamed skin increases absorption.

2. Occlusive dressings: Using plastic or bandages over the steroid significantly increases absorption.

3. Surface area: Larger treated areas lead to higher systemic absorption.

4. Duration and Frequency: Long-term or overly frequent use increases the systemic load.

5. Inflammation: Inflammation widens vessels and weakens the barrier, facilitating faster absorption.

Quantitative Dosing: The Fingertip Unit (FTU)

To ensure proper application and avoid under-dosing or over-dosing, the Fingertip Unit (FTU) is used.

• Definition: One FTU is the amount of product expressed from a tube that covers the tip of an adult's index finger from the very end to the first skin crease (distal skin crease).

• Equivalence: $1 \, \text{FTU} \approx 0.5 \, \text{g}$ of ointment or cream.

Quantity Required for One Application

• Calculation Example: An adult male treating his trunk twice daily for one week would require $49 \, \text{g}$ of ointment ($3.5 \, \text{g} \times 2 \, \text{applications/day} \times 7 \, \text{days}$).

Adverse Effects

Cutaneous (Local) Side Effects

Potent drugs, occlusion, thin skin, and advanced age increase the risk. These may appear within $2 \text{ to } 3 \, \text{weeks}$ of daily use:

• Atrophy: Thinning of the skin.

• Telangiectasia: Dilation of small blood vessels near the surface of the skin.

• Striae: Stretch marks.

Systemic Side Effects

When absorbed into the bloodstream, they can cause internal issues, most notably:

• HPA Axis Suppression: Suppression of the Hypothalamic-Pituitary-Adrenal axis.

• Complications: This may lead to hypothyroidism, weakened immunity, or changes in blood pressure and glucose levels.

• High-Risk Populations: The elderly and very young are more vulnerable due to thinner skin and higher absorption rates.

Additional Therapeutic Guidelines

• Antimitotic effect: Steroids slow down cell division, which is beneficial in conditions like psoriasis.

• Collagen inhibition: They can reduce the synthesis of collagen fibers.

• Tachyphylaxis: Continued use can lead to the skin no longer responding to the medication.

• Contraindication - Antifungals: Avoid mixing topical steroids with antifungals, as steroids can weaken the skin's local immunity and allow fungal infections to spread further.

• Infection Check: Before beginning treatment, ensure there is no underlying infection (e.g., fungal).

• Lab Tests: For patients on long-term or large-area treatment, laboratory tests may be necessary to monitor for systemic effects.