What is the mechanism of action (MOA) of Drysol (aluminum chloride hexahydrate)?

Mechanism of Action of Drysol (Aluminum Chloride Hexahydrate)

Drysol (aluminum chloride hexahydrate) works primarily by forming complexes with keratin in the sweat duct, causing obstruction and atrophy of the eccrine sweat glands, which leads to reduced sweat production.

Primary Mechanism of Action

Aluminum chloride hexahydrate, the active ingredient in Drysol, acts through several mechanisms:

1. Sweat Duct Obstruction:

   • Forms precipitates with proteins in the sweat ducts
   • Creates physical plugs that block sweat from reaching the skin surface
   • Causes mechanical obstruction of eccrine sweat gland openings 1, 2

2. Atrophy of Sweat Glands:

   • With continued use, causes functional atrophy of the eccrine sweat glands
   • Reduces the overall sweat production capacity over time 3

3. Chemical Reaction:

   • The aluminum ions (Al³⁺) react with keratin proteins in the stratum corneum
   • Forms aluminum-protein complexes that physically block sweat ducts 2

Formulation Factors

The efficacy of Drysol is enhanced by its specific formulation:

• Concentration: Typically available as 20% or 12% aluminum chloride hexahydrate
• Vehicle: Dissolved in absolute ethanol (anhydrous alcohol)
• pH: Acidic formulation enhances penetration and efficacy
• Enhanced formulations: When combined with 2% salicylic acid in a gel base, shows decreased irritation while maintaining efficacy 3

Pharmacodynamics

• Onset of Action: Effects typically begin within 24-48 hours of application 4
• Duration of Effect: Persists for approximately 24-48 hours after discontinuation 4
• Maximum Effect: Achieved after several applications, with cumulative benefit over 1-2 weeks of regular use 2, 4

Application Considerations

For optimal efficacy and reduced side effects:

• Apply to completely dry skin to prevent formation of hydrochloric acid
• Apply at bedtime when sweat production is naturally lower
• Wash off in the morning to reduce irritation
• Occlusion with plastic wrap can enhance efficacy but may increase irritation 2

Common Side Effects

The most common adverse effects are related to skin irritation:

• Burning sensation
• Itching
• Erythema
• Contact dermatitis
• Skin irritation (can be severe enough to require discontinuation in some patients) 3

Clinical Pearls

• Aluminum chloride hexahydrate is considered first-line therapy for mild to moderate hyperhidrosis 3
• Lower concentrations (1%) can be effective when delivered via iontophoresis for palmar hyperhidrosis 5
• For patients with severe irritation from standard formulations, the combination with salicylic acid in a gel base may provide better tolerability 3
• Can be used in combination therapy with botulinum toxin type A for enhanced effect in moderate to severe hyperhidrosis 1

Understanding the mechanism of action helps explain both the efficacy and side effect profile of Drysol in the management of hyperhidrosis.