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For decades, dermatology practices routinely relied on compounded cantharidin for the treatment of both warts and molluscum contagiosum. It was inexpensive, easy to store in-office, and—importantly— one of the few treatments tolerated by young children who were fearful of needles or liquid nitrogen.
That long-standing status quo changed in 2023, when Verrica Pharmaceuticals obtained FDA approval for YCANTH, a specific formulation of cantharidin approved for molluscum contagiosum. With that approval came market exclusivity and a key regulatory consequence: compounding pharmacies were no longer permitted to produce products considered “essentially copies” of the approved drug.
In practical terms, this did not mean that cantharidin itself became illegal, nor that it became the sole property of YCANTH. What it meant was narrower—but far more disruptive. Trusted compounding pharmacies across the country began receiving cease-and-desist letters advising them to halt production of cantharidin products that could be viewed as substitutes for the FDA-approved formulation. One by one, suppliers exited the space, and dermatology practices lost access to the familiar, shelf-stocked cantharidin they had relied on for years.
Compounded alternatives—like that seen here—are formulated to be 'meaningfully different' from YCANTH, either through changes in concentration, the addition of other ingredients, or a combination of both.
NOTE: This content is informational only and is not sponsored; no reimbursement or compensation was received.
The Ripple Effect Beyond Molluscum
One of the most confusing aspects of this transition was how an FDA approval limited to molluscum contagiosum could so thoroughly disrupt cantharidin use for warts, which historically represented a significant portion of in-office treatment.
On its face, the disconnect seemed obvious. YCANTH’s approval did not make cantharidin proprietary, nor did it grant authority to prohibit cantharidin use for verruca. The approval was specific to a particular formulation and a particular indication, and nothing in that approval prevented clinicians from treating warts with cantharidin in principle.
To understand the disruption, one must look at how FDA compounding rules are structured. Compounding restrictions hinge not on diagnosis, but on product similarity. Once YCANTH became FDA-approved, compounding pharmacies were no longer permitted to produce products considered essentially copies—meaning products with the same active ingredient, similar concentration, dosage form, and route of administration that could function as a clinical substitute, regardless of intended use.
As a result, even a straight cantharidin topical solution intended for wart treatment could be viewed as a functional substitute for the approved molluscum product. This regulatory framing explains why many pharmacies exited the cantharidin space entirely, even though wart treatment itself was never prohibited.
This same dynamic also explains the disappearance of combination products such as “Cantharidin Plus,” which paired cantharidin with salicylic acid and were widely used for verruca. Although these products were neither identical to YCANTH nor approved for the same indication, they occupied a regulatory gray zone. Many were still topical solutions, used in overlapping patient populations, and could plausibly be viewed as near substitutes depending on how similarity was interpreted.
In the immediate aftermath of YCANTH’s approval, enforcement boundaries were unclear. Compounding pharmacies were faced with a newly approved product, broad assertions about essentially copies, and legal correspondence that—while carefully worded—carried an unmistakable message:
Proceed at your own risk.
For large compounding pharmacies, particularly 503B outsourcing facilities, the risk calculus was asymmetric. Continuing to compound cantharidin products carried the possibility of significant regulatory or legal consequences, while stopping carried primarily commercial downsides. Faced with that imbalance, many chose the most conservative path available: exiting the cantharidin category altogether.
With hindsight, this early pullback looks less like an outright ban and more like a rational response to regulatory uncertainty. Over time, the contours of what is—and is not—defensible have become clearer, setting the stage for the more selective practices that followed.
What Has Not Changed
From a regulatory standpoint, very little has materially changed since the months immediately following YCANTH’s approval.
- There is still no FDA-approved generic cantharidin-only product.
- YCANTH remains the only FDA-approved formulation, specifically for molluscum contagiosum.
- Compounding pharmacies therefore remain restricted from producing products that would be considered essentially copies of that approved medication.
YCANTH has not been listed on the FDA drug shortage list, meaning shortage-based compounding exceptions do not apply. Large 503B outsourcing facilities, in particular, continue to approach cantharidin with caution due to their higher regulatory exposure.
In short, the rules themselves have not softened. What has settled, however, is the initial “fog of war” triggered by the now-infamous cease-and-desist letters sent during the early rollout of YCANTH.
Where Things Stand
Rather than a full return to pre-2023 workflows—or a complete abandonment of cantharidin altogether—practices and pharmacies have adapted in narrower, more selective ways.
Some compounding pharmacies now prepare combination topical formulations that include cantharidin alongside other active ingredients, most commonly for wart treatment. These formulations differ meaningfully from the FDA-approved product in composition, concentration, and clinical behavior, placing them in a different regulatory posture than a straight cantharidin-only product for molluscum.
At the same time, pharmacies and clinicians have become far more deliberate about how these products are described, prescribed, and documented, particularly with respect to indication and patient specificity.
YCANTH itself has found a role—but not a universal one. Many practices reserve it for select cases where coverage, patient age, or lesion burden make it a reasonable option, rather than treating it as a wholesale replacement for historical in-office cantharidin use.
The Practical Reality for Clinics
The net result is not a clean workaround, but a new equilibrium.
Practices that once took for granted cantharidin’s role as a routine, shelf-stocked tool now operate under a more fragmented model:
- YCANTH for some patients
- Compounded alternatives for others
When compounded alternatives are prescribed, their non-overlapping ingredients and/or concentrations—which prevent them from being classified as essentially copies of YCANTH—must be explicitly factored into clinical and operational decision-making.
Looking Ahead
Absent a change in FDA guidance, expiration of exclusivity, or approval of additional competitors, this framework is likely to persist.
Proponents of YCANTH may argue that FDA approval and exclusivity were necessary to impose standardization, safety oversight, and manufacturing controls on a drug that had long existed outside the approved pharmaceutical framework. Without exclusivity, they contend, there would have been little incentive to fund the trials and regulatory work required to legitimize a decades-old compound.
Critics, however, may argue that while the stated goals emphasized standardization and oversight, the practical effect—and economic incentive—was to transform a long-standing, low-cost clinical practice into an exclusive, revenue-generating product category.
For readers interested in the original 2023 article, see:
Why Is Cantharidin So Hard to Find Now?
(Medium, 2023)