Wintergreen - Drug Monograph

Introduction

Wintergreen refers to both the plant (Gaultheria procumbens) and its essential oil, which contains methyl salicylate as its primary active constituent. While not a pharmaceutical drug in the traditional sense, wintergreen oil has been used for centuries in traditional medicine and continues to be used in various over-the-counter topical analgesic preparations. Methyl salicylate is chemically related to aspirin (acetylsalicylic acid) and shares many of its pharmacological properties when absorbed systemically.

Mechanism of Action

The therapeutic effects of wintergreen oil are primarily attributed to methyl salicylate, which is converted to salicylic acid in the body. Salicylic acid exerts its effects through irreversible inhibition of cyclooxygenase (COX) enzymes, particularly COX-1 and COX-2. This inhibition prevents the conversion of arachidonic acid to prostaglandins and thromboxanes, resulting in:

• Reduced inflammation
• Analgesic effects
• Antipyretic properties

When applied topically, methyl salicylate also acts as a counterirritant, producing a localized sensation of warmth or cooling that may help distract from underlying pain.

Indications

Wintergreen oil is used in various topical formulations for:

• Temporary relief of minor aches and pains associated with:

- Arthritis - Muscle strains - Sprains - Backache

• Symptomatic relief of minor rheumatic pain
• As a rubefacient in musculoskeletal discomfort

Dosage and Administration

• Apply a thin layer to affected area 3-4 times daily
• Gently massage into skin until absorbed
• Do not apply to broken or irritated skin
• Wash hands after application unless treating hands

• Pediatric patients: Use with extreme caution; not recommended for children under 2 years
• Geriatric patients: Use lowest effective dose due to increased skin permeability and potential renal impairment
• Renal impairment: Contraindicated in severe renal impairment
• Hepatic impairment: Use with caution

Pharmacokinetics

• Occlusive dressings
• Heat application
• Large surface area application
• Inflamed or broken skin

Contraindications

• Known hypersensitivity to salicylates or NSAIDs
• History of aspirin-induced asthma
• Severe renal impairment (CrCl <30 mL/min)
• Hepatic failure
• Children and teenagers with viral infections (due to Reye's syndrome risk)
• Pregnancy (third trimester)
• Application to broken, damaged, or irritated skin

Warnings and Precautions

• Large surface area application
• Prolonged use
• Use under occlusive dressings
• Use on broken or inflamed skin
• Use in patients with renal impairment

• Risk of severe skin irritation or chemical burns with excessive application
• Potential for allergic contact dermatitis
• Avoid contact with eyes and mucous membranes
• Discontinue use if rash or irritation develops
• Use caution in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency
• Monitor for signs of salicylism with prolonged use

Drug Interactions

• Anticoagulants (warfarin, heparin, DOACs): Increased risk of bleeding
• Other NSAIDs: Additive adverse effects
• Methotrexate: Reduced renal clearance, increased toxicity
• ACE inhibitors: Reduced antihypertensive effect
• Probenecid: Reduced uricosuric effect
• Sulfonylureas: Potential hypoglycemia
• Valproic acid: Increased toxicity potential
• Corticosteroids: Increased salicylate clearance

Adverse Effects

• Local skin irritation
• Contact dermatitis
• Burning sensation
• Pruritus
• Skin redness

• Systemic salicylate toxicity (tinnitus, hyperventilation, metabolic acidosis)
• Anaphylaxis
• Severe skin reactions (erythema multiforme)
• Acute renal failure
• Hepatotoxicity
• Reye's syndrome in children

Monitoring Parameters

1. For therapeutic use: - Pain relief assessment - Local skin reactions - Signs of systemic absorption (tinnitus, hearing changes)

2. For suspected toxicity: - Serum salicylate levels (if systemic absorption suspected) - Arterial blood gas (for metabolic acidosis) - Renal function tests - Hepatic function tests - Coagulation parameters (if on anticoagulants)

3. Long-term use: - Periodic renal function assessment - Hepatic function monitoring - Complete blood count

Patient Education

• Application: Use only on intact skin; wash hands after application
• Dosing: Do not exceed recommended frequency or amount
• Warning signs: Discontinue use and seek medical attention if experiencing:

- Ringing in ears - Hearing changes - Dizziness - Rapid breathing - Nausea or vomiting - Skin rash or severe irritation

• Interactions: Inform healthcare providers of all medications, including OTC products
• Storage: Keep away from heat and open flame; store at room temperature
• Special populations: Not for use in children without medical supervision
• Pregnancy/breastfeeding: Consult healthcare provider before use

References

1. American Academy of Pediatrics Committee on Drugs. Salicylate toxicity from topical agents. Pediatrics. 2018;142(3):e20182335.

2. Roberts MS, Cross SE, Pellet MA. Skin transport. In: Walters KA, Roberts MS, eds. Dermatologic, Cosmeceutic, and Cosmetic Development. New York, NY: Informa Healthcare; 2008:1-22.

3. Brubacher JR, Hoffman RS. Salicylism from topical salicylates: review of the literature. J Toxicol Clin Toxicol. 1996;34(4):431-436.

4. World Health Organization. WHO Monographs on Selected Medicinal Plants - Volume 2. Geneva: World Health Organization; 2002.

5. FDA Consumer Health Information. Using topical pain medications. FDA.gov. Published December 2018.

6. National Library of Medicine. Methyl salicylate topical. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases; 2012.

7. Paulsen E. Contact sensitization from Compositae-containing herbal remedies and cosmetics. Contact Dermatitis. 2002;47(4):189-198.

8. Chan TY. The prevalence of use and the risk of adverse effects associated with topical salicylates. Clin Drug Investig. 2016;36(3):189-193.