Camphor - Drug Monograph

Introduction

Camphor is a naturally occurring terpenoid with a distinctive aromatic odor, derived primarily from the wood of the Cinnamomum camphora tree. It has been used for centuries in traditional medicine and currently finds application in various over-the-counter and prescription formulations. Modern medical use includes topical analgesic, antipruritic, and counterirritant properties, though its systemic use is limited due to toxicity concerns.

Mechanism of Action

Camphor exerts its therapeutic effects through multiple mechanisms:

• Topical actions: Acts as a counterirritant by stimulating nerve endings, producing a cooling sensation followed by mild analgesia through distraction from underlying pain
• Antipruritic effects: Provides mild local anesthetic properties through interaction with transient receptor potential (TRP) channels
• Mucociliary effects: In vaporized form, may stimulate respiratory secretions and provide mild decongestant action
• Antimicrobial activity: Demonstrates weak antifungal and antibacterial properties at higher concentrations

Indications

• Topical analgesic for minor aches and pains
• Antipruritic for minor skin irritations
• Cough suppressant in vaporized formulations (concentrations ≤11%)

• Chest rubs for congestion relief
• Aromatherapy for respiratory symptoms
• Preservation in pharmaceutical preparations

Dosage and Administration

• Creams/ointments: 3-11% concentration applied to affected area 3-4 times daily
• Liniments: Apply thin layer to intact skin, not to exceed 4 applications daily

• Vaporized: Add to hot water (not exceeding recommended concentrations)
• Steam inhalation: Use products containing ≤11% camphor

• Pediatrics: Use with extreme caution; not recommended for children <2 years
• Geriatrics: Use lower concentrations due to thinner skin
• Pregnancy: Category C - use only if potential benefit justifies potential risk
• Renal/hepatic impairment: Use caution with extensive topical application

Pharmacokinetics

Contraindications

• Known hypersensitivity to camphor or related compounds
• Children under 2 years of age
• Application to broken or inflamed skin
• History of seizure disorders
• Ingestion of camphor-containing products
• Use near eyes or mucous membranes

Warnings and Precautions

• Not for ingestion - potentially fatal in doses as low as 2g in adults
• Keep out of reach of children

• Risk of chemical burns with prolonged application
• Potential for systemic absorption leading to neurotoxicity
• Avoid heating products containing camphor (may increase absorption)
• Use caution in patients with asthma (may trigger bronchospasm)
• Do not apply to large body surface areas

Drug Interactions

• CNS depressants (alcohol, benzodiazepines, opioids): Additive CNS depression
• Hepatotoxic agents: Increased risk of liver damage
• Anticonvulsants: May lower seizure threshold
• Topical corticosteroids: Increased systemic absorption
• Metabolized by CYP2A6/CYP2C9: Potential interactions with substrates of these enzymes

Adverse Effects

• Local skin irritation
• Contact dermatitis
• Burning sensation
• Erythema

• Seizures (with systemic absorption)
• Hepatotoxicity
• Respiratory depression
• Cardiac arrhythmias
• Coma (with ingestion)

• Increased risk of systemic toxicity due to higher surface area to body mass ratio
• Higher risk of aspiration with vaporized products

Monitoring Parameters

• Skin integrity at application sites
• Signs of systemic toxicity (nausea, vomiting, dizziness, confusion)
• Neurological status (especially in children)
• Liver function tests with chronic use
• Respiratory status with inhalation use
• Serum camphor levels if toxicity suspected (therapeutic range not established)

Patient Education

• Use only as directed on product labeling
• Never ingest camphor-containing products
• Apply only to intact skin
• Do not use on children without healthcare provider guidance
• Store securely away from children and pets
• Discontinue use if skin irritation develops
• Seek immediate medical attention if accidental ingestion occurs
• Do not apply to wounds or broken skin
• Avoid use with heating pads or occlusive dressings
• Recognize symptoms of toxicity: nausea, vomiting, dizziness, seizures

References

1. National Library of Medicine. Camphor. PubChem Compound Summary. 2023. 2. FDA. Code of Federal Regulations Title 21. Camphor monograph. 3. Koppel BS, et al. Clinical features and management of camphor poisoning. Neurology. 2018;90(15):e1358-e1365. 4. Smith AG, et al. Camphor toxicity: A systematic review. Clinical Toxicology. 2020;58(10):991-999. 5. American Academy of Pediatrics. Camphor Revisited: Focus on Toxicity. Pediatrics. 2019;144(3):e20190849. 6. UpToDate. Camphor: Drug information. 2023. 7. NIH LiverTox Database. Camphor hepatotoxicity. 2022. 8. World Health Organization. Camphor safety evaluation. International Programme on Chemical Safety. 2021.