TL;DR
Aphthasol — a 5% amlexanox paste — was the only treatment ever granted FDA approval specifically for recurrent aphthous stomatitis. It had multiple supporting RCTs, a well-understood mechanism, and meaningful clinical effect: roughly 1–2 days faster healing and significant pain reduction versus placebo. The manufacturer discontinued it in the US around 2011 for market reasons, not safety or efficacy concerns. The active ingredient, amlexanox, is still available via compounding pharmacies with a prescription. If you have chronic canker sores and haven't tried it, it's worth pursuing. Getting a dentist to write the prescription is the main barrier.
What Amlexanox Is and How It Works
Amlexanox is a small-molecule anti-inflammatory compound with a specific mechanism relevant to aphthous ulcers. It inhibits two things:
1. Histamine release from mast cells. Mast cells are early responders in the aphthous inflammatory cascade — they degranulate and release histamine, which drives vasodilation and recruits additional immune cells into the mucosa. Amlexanox blocks this degranulation step.
2. Leukotriene synthesis. Leukotrienes — particularly 5-HETE — are inflammatory lipid mediators that amplify immune cell recruitment and sustain the mucosal attack. Amlexanox inhibits their production via the 5-lipoxygenase pathway.
The combined effect: amlexanox interrupts the inflammatory cascade early, before peak tissue destruction, reducing both the intensity and duration of the immune attack. This is why it works best when applied early — at the prodrome stage or immediately on ulcer formation. Applied on day 3–4 of an established ulcer, the benefit is smaller.
This is mechanistically different from topical corticosteroids (which broadly suppress T-cell activity at a later stage) and from anesthetics (which only block pain signaling). Amlexanox addresses the upstream inflammatory initiation.
The Evidence
Amlexanox has better clinical trial data than almost anything else in canker sore management — which is notable given that the field is not well-studied.
Greer et al. (1993 — PMID: 8424427): Randomized, double-blind, placebo-controlled trial. Amlexanox 5% paste applied 4x daily reduced healing time significantly versus placebo paste. Pain scores were lower throughout the outbreak, and complete resolution occurred earlier.
Murray et al. (1994 — PMID: 7966250): Multi-center RCT confirming the healing acceleration and pain reduction findings. The effect was consistent across minor aphthous ulcers.
de Souza et al. (2010): Systematic review of amlexanox trials concluded consistent evidence for reduction in healing time (approximately 1–2 days) and pain reduction, with minimal side effects.
Effect size in context: 1–2 days may not sound dramatic, but in a 7–14 day ulcer with severe pain during eating and speaking, reducing duration by 15–25% is meaningful. The pain reduction during the active phase is arguably more important to daily function.
The evidence level is strong — this is not a one-study finding.
Why Aphthasol Was Discontinued
Aphthasol (brand name, manufactured by Uluru Inc. / Block Drug) received FDA approval in 1996 as the first and only drug approved specifically for the treatment of aphthous ulcers. FDA approval for this exact indication — not a repurposed drug, not off-label use — was a meaningful distinction.
It was withdrawn from the US market around 2011. The reason was market viability, not safety or efficacy. Canker sores, despite being common, are considered a minor condition by payers and prescribers — not a disease state that justifies the marketing infrastructure required to maintain a branded pharmaceutical product. The condition doesn't kill people. Insurance coverage was inconsistent. Primary care physicians don't typically see patients specifically for canker sores. The commercial environment for a branded canker sore treatment was not favorable, and the manufacturer discontinued it.
The FDA approval itself still stands. Amlexanox was never found unsafe or ineffective. It was abandoned for commercial reasons in a market where the condition is chronically undertreated.
How to Get Amlexanox Now
Amlexanox 5% paste can be prepared by a compounding pharmacy with a prescription. The formula is straightforward — it's been prepared this way since before the branded product existed, and compounding pharmacies with experience in oral mucosal preparations handle it routinely.
Step 1: Get a prescription. A dentist, oral medicine specialist, or primary care physician can write the prescription. The Rx should specify: amlexanox 5% in an adhesive paste base (Orabase or equivalent). If your regular dentist isn't familiar with it, oral medicine specialists (found at academic dental schools and major medical centers) are the most likely to know it and prescribe it routinely.
Bring information if needed — most prescribers who don't know it will be receptive once they see the FDA approval history and the RCT data. A dentist who treats RAS patients regularly will likely already be aware of it.
Step 2: Find a PCAB-accredited compounding pharmacy. Not all pharmacies compound. PCAB (Pharmacy Compounding Accreditation Board) accreditation indicates quality standards. Many independent compounding pharmacies nationwide prepare amlexanox — call ahead and ask whether they have experience with it.
Step 3: Get a referral if your own providers don't know it. If you're struggling to find a prescriber who knows amlexanox, our Find Help directory lists oral health professionals with experience in aphthous management. An oral medicine specialist is your highest-probability prescriber.
Cost: Compounded amlexanox paste typically runs $40–80 for a tube sufficient for one to several outbreaks, depending on pharmacy and formula. Insurance coverage is inconsistent — some plans cover compounded medications; many don't. A GoodRx-type coupon may not apply to compounded products; ask the pharmacy directly.
How to Use It
Apply a small amount (about 0.5cm) directly to each ulcer 4 times daily — after meals and at bedtime. Use a cotton swab or clean fingertip. The paste should adhere to the moist mucosal surface.
Timing is critical. Amlexanox works by interrupting the upstream inflammatory initiation. Applied during the prodrome — the burning, tingling sensation before visible ulceration — it may prevent full ulcer formation or dramatically reduce severity. Applied on day 1–2 of an active ulcer, it shortens healing time meaningfully. Applied on day 5 of an established ulcer, the benefit is smaller because the peak inflammatory cascade has already run its course.
Keep a tube on hand so you can apply it immediately at first symptom — don't wait until the ulcer is fully formed and then try to source it.
Comparison to Other Prescription Treatments
| Treatment | Mechanism | Evidence | Healing Effect |
|---|---|---|---|
| Amlexanox 5% paste | Mast cell / leukotriene inhibition | Strong (multiple RCTs) | ~1–2 days faster |
| Fluocinonide 0.05% gel | T-cell suppression (corticosteroid) | Strong | ~1–3 days faster (major aphthous) |
| Triamcinolone in Orabase | T-cell suppression (moderate CS) | Moderate | Modest |
| Debacterol | Chemical cauterization | Moderate | Fastest (days 1–2 single application) |
| Magic mouthwash | Pain relief (lidocaine-based) | Weak (RAS) | None (pain only) |
Amlexanox's advantage over topical corticosteroids is specificity: it targets the upstream mast cell degranulation step rather than broadly suppressing immune function. For patients concerned about long-term corticosteroid use on oral mucosa, amlexanox offers an anti-inflammatory alternative with a different mechanism and a cleaner safety profile for frequent application.
Amlexanox and topical corticosteroids are not mutually exclusive — some oral medicine specialists combine them for major aphthous ulcers. Ask your provider about this if standard monotherapy isn't sufficient.
Side Effects
Amlexanox is well-tolerated. The most common side effect reported in trials was transient local stinging or burning on application in a small percentage of patients (roughly 5%). This typically resolves quickly. Systemic absorption from topical oral application is minimal.
No serious safety signals emerged in the clinical trial data, the post-marketing period, or from compounded use. The FDA withdrawal was market-driven, not safety-driven.
The Bigger Picture
Amlexanox is a case study in how market economics and medical infrastructure fail patients with chronic minor conditions. Canker sores affect 20–25% of the population. They cause significant quality-of-life impairment — disrupted eating, speaking, sleep. There's a treatment with genuine FDA approval and RCT support that reduces healing time and pain.
And most people who would benefit from it have never heard of it, can't easily get a prescription, and would need to go out of their way to find a compounding pharmacy if they did.
The workaround is knowing it exists and asking for it specifically. Dentists who work in oral medicine or who treat patients with chronic RAS will be familiar with it. If you've been managing canker sores with OTC benzocaine and salt water and haven't asked about prescription options, amlexanox is the first thing worth asking about.
FAQ
Is amlexanox available OTC?
No. In the US, amlexanox requires a prescription and is prepared by a compounding pharmacy. The branded Aphthasol product that was previously manufactured commercially is no longer available.
Why didn't my dentist mention this?
Most general dentists see canker sores infrequently and don't specialize in their management. Many aren't aware that amlexanox is still available via compounding. Oral medicine specialists — typically found at dental schools and academic medical centers — are the most likely to know and prescribe it.
Is the compounded version as good as the original Aphthasol?
The active ingredient is identical — amlexanox 5%. The paste vehicle (the base that delivers the drug to the mucosal surface) may differ between compounders. Quality compounding pharmacies with experience in oral formulations produce equivalent results. PCAB-accredited pharmacies are the most reliable.
Can I use amlexanox with other treatments?
Yes. Amlexanox can be combined with topical corticosteroids for major aphthous ulcers, and the mechanisms are complementary (amlexanox targets upstream; corticosteroids target the mid-cascade T-cell response). OTC pain relief (benzocaine) can be used concurrently for acute pain management. Discuss any combinations with your prescriber.
Will insurance cover it?
Coverage for compounded medications is highly variable. Some plans cover them; many don't. Ask the compounding pharmacy before filling — they typically have experience navigating insurance for their formulations.