Prescribing Viscous Lidocaine 2% for Canker Sores
Prescribe lidocaine 2% viscous solution at 15 mL per application, instructing the patient to swish in the mouth for 1-2 minutes before spitting out, repeated every 3 hours as needed, particularly before meals. 1
Dosing and Administration
- The standard prescription is 15 mL of viscous lidocaine 2% held in the mouth for 1-2 minutes, then expectorated (not swallowed), applied every 3 hours as needed 1
- Timing applications before meals maximizes comfort during eating 1
- The maximum daily dose must not exceed 9 mg/kg of lean body weight from all sources combined, which translates to approximately 31.5 mL per day for a 70 kg patient 1
Critical Safety Instructions for Patients
- Instruct patients to always spit out the solution after swishing to minimize systemic absorption and reduce toxicity risk 1
- Warn patients to monitor for toxicity symptoms including:
- Tingling of tongue or lips
- Light-headedness or dizziness
- Tinnitus (ringing in ears)
- Slurred speech
- Muscle twitching 1
- If any of these symptoms occur, discontinue use immediately and seek medical attention 1
Enhanced Formulations for Severe Cases
For particularly severe or refractory canker sores, consider combination approaches:
- Viscous lidocaine 2% plus nystatin oral suspension can provide concurrent antifungal coverage if candidiasis is suspected 1
- Adding sodium bicarbonate to the formulation helps neutralize the oral environment and may enhance comfort 1
- Benzydamine hydrochloride rinse every 3 hours serves as an alternative anti-inflammatory option 1
Adjunctive Supportive Measures
Beyond the lidocaine prescription, recommend:
- White soft paraffin ointment to lips every 2 hours for lip protection 1
- Warm saline mouthwashes daily for cleansing 1
- Antiseptic oral rinses twice daily to reduce bacterial colonization 1
Common Pitfalls to Avoid
- Never prescribe viscous lidocaine for swallowing or gargling—this dramatically increases systemic absorption and toxicity risk 1
- Avoid prescribing multiple lidocaine-containing products simultaneously (e.g., viscous lidocaine plus lidocaine patches or other topical preparations), as this increases cumulative dose and toxicity risk 2
- Do not apply within 4 hours of other local anesthetic interventions 2
- Failing to provide clear "spit, don't swallow" instructions is a critical error that can lead to systemic toxicity 1
Clinical Context
While viscous lidocaine provides excellent topical analgesia for oral mucosal pain, it should be positioned as an adjunctive option when standard analgesics (acetaminophen, NSAIDs, or throat lozenges) provide insufficient relief 1. The prescription serves as a targeted intervention for breakthrough pain rather than first-line monotherapy.