Single-source transdermal patches in the Orange Book: 385 products, 43% no generic

The FDA Orange Book lists 385 transdermal (patch) drug products across 23 distinct active ingredients and fixed-dose combinations (run date June 10, 2026). Of those 23 molecules, 10 — 43.5 percent — are single-source: a brand NDA is on file but no ANDA has been approved at any strength, so no FDA-rated generic exists. Unlike orally inhaled products, transdermal is heavily genericized at the product level — 231 of the 385 products, 60.0 percent, carry an AB therapeutic-equivalence code that lets a pharmacist automatically substitute a generic at the point of dispensing. The concentration sits in a specific set of brand-only patches — Neupro (rotigotine), Adlarity (donepezil), Xelstrym (dextroamphetamine), Secuado (asenapine), Sancuso (granisetron), Emsam (selegiline), Twirla (ethinyl estradiol/levonorgestrel), Climara Pro, CombiPatch, and Ionsys — four of which carry zero listed patents yet have still never attracted a generic.

This is a narrow, route-specific read of the FDA Orange Book for the transdermal segment — adhesive patches delivering drug across intact skin, spanning hormone replacement, analgesia, neurology, smoking cessation, and antiemesis. Every figure is computed from the public FDA Orange Book (Approved Drug Products with Therapeutic Equivalence Evaluations), run date June 10, 2026. For the database-wide Orange Book picture, see the companion therapeutic-equivalence analysis of 48,000 products; for the route-parallel niches where generic entry is even harder, see single-source inhaled drugs and single-source ophthalmic drops. This article stays on transdermal patches.

Methodology, in one paragraph

The source is the Orange Book products.csv (48,215 total products), filtered to records whose route contains TRANSDERMAL (385 products; one iontophoresis-delivered product is included). "Distinct molecule" means a distinct Ingredient string, which treats fixed-dose combinations (for example, estradiol; levonorgestrel) as their own molecule, separate from estradiol monoproduct and from ethinyl estradiol; levonorgestrel. An ingredient is single-source when the Orange Book contains at least one NDA (Appl_Type = N) product for it but no ANDA (Appl_Type = A) product at any strength — that is, no FDA-approved generic exists. AB-substitutability is read from the TE_Code field: a product beginning with AB is rated therapeutically equivalent and pharmacy-substitutable. Patent and exclusivity cliffs come from joining each single-source molecule's NDA application numbers to the patents.csv file; "latest expiry" is the maximum patent-expiry year across all patents on those NDAs. A molecule with a single-source NDA but zero rows in patents.csv for its application is what the article calls "zero listed patents." A single-source NDA can sit on top of a discontinued brand presentation — the Orange Book keeps the NDA but no product is actively shipped — and those cases are flagged in the patent table, because a discontinued single-source NDA reflects an absent-generic gap rather than an active brand monopoly.

The headline picture

Transdermal is a small route in the Orange Book — 385 of 48,215 products, under 1 percent — but it is bifurcated in a way the headline single-source rate understates. The route is mature and well-genericized at the product level, yet a hard core of brand-only patches has resisted generic entry for years or decades:

The dosage-form mix explains where the generic density concentrates. Of the 385 products, 224 are extended-release film patches (the modern estradiol, fentanyl, and testosterone platforms), 71 are older "systems" (nitroglycerin, clonidine, scopolamine), 78 are transdermal gels and metered gels (testosterone), and a handful are metered solutions, an ointment, and a spray. The 13 generic-available molecules — estradiol (69 ANDAs), fentanyl (52), testosterone (30), buprenorphine (25), nitroglycerin (20), rivastigmine (18), clonidine (12), scopolamine (7), ethinyl estradiol/norelgestromin (4), methylphenidate (4), nicotine (3), and oxybutynin (1) — account for almost all of the AB volume. The 10 single-source molecules account for almost none of it.

The contrast with the orally inhaled route is instructive: inhaled is single-source at 65.1 percent of molecules and only 6.7 percent AB-substitutable, because device and bioequivalence complexity blocks generics wholesale. Transdermal is the opposite at the product level — 60 percent AB — yet still holds a 10-molecule single-source core where the barriers are molecule- and formulation-specific rather than route-wide.

Single-source means two different things here

As with inhalers, a transdermal molecule can be single-source for two very different reasons, and the Orange Book patent column makes the distinction visible:

1. Single-source behind an active patent estate. Neupro (rotigotine, NDA 021829) lists 30 patents with the latest expiring in 2032. Adlarity (donepezil, NDA 212304) lists 22 patents to 2038. Xelstrym (dextroamphetamine, NDA 215401) lists 12 patents, four of which run to 2042. These are on-patent single-source molecules: an ANDA sponsor can file but will face paragraph-IV litigation and cannot launch until the patents expire or are invalidated.

2. Single-source with no listed patents at all. Four of the ten single-source transdermal molecules — Climara Pro (estradiol/levonorgestrel, NDA 021258), CombiPatch (estradiol/norethindrone acetate, NDA 020870), Sancuso (granisetron, NDA 022198), and Emsam (selegiline, NDA 021336) — each have zero patents in the current Orange Book extract. Their composition patents have expired, yet no generic has cleared FDA. CombiPatch was approved in 1998 and Climara Pro in 2003; both have been single-source for two decades.

The access implication is the same one the inhaled analysis surfaces: patent-cliff modeling alone under-predicts generic entry. A transdermal molecule can pass its last patent expiry and still stay single-source for years because the formulation-matching and adhesion/irritation bioequivalence bar, not the Orange Book patent column, is the binding constraint.

The patent picture for the brand-only patches

The single-source transdermal molecules sort cleanly by how far out their protection runs, and four of them run to nothing:

Two structural points fall out of this table. First, the newest entrants have the longest runways: the 2022 central-nervous-system patches (Xelstrym, Adlarity) and the 2019 antipsychotic patch (Secuado) carry protection into the late 2030s and 2040s. A payer modeling the transdermal pipeline over the next decade should assume the on-patent single-source layer (Xelstrym, Adlarity, Secuado, Ionsys) thickens before it thins.

Second, the four zero-patent molecules are the anomaly: their exclusivity expired years ago but the Orange Book still lists no ANDA. The barrier is the same transdermal bioequivalence standard that FDA has refined across a decade of generic-drug-user-fee science programs — a generic patch must demonstrate pharmacokinetic bioequivalence and non-inferior adhesion and no worse skin irritation and sensitization than the reference product, with explicit evaluation of heat effects. FDA has issued product-specific guidance for each of the zero-patent molecules (rotigotine, granisetron/Sancuso, and selegiline/Emsam all have draft product-specific guidances), yet no applicant has cleared that bar for any of the four.

Why rotigotine, Sancuso, and Emsam have guidance but no generic

The three zero-patent neurology patches illustrate how a published FDA development pathway does not by itself produce a generic. FDA's product-specific guidance for rotigotine transdermal system has been on the books since June 2012 and has been revised four times, most recently November 2019; it specifies the single-dose crossover pharmacokinetic bioequivalence study, the adhesion study, and the irritation-and-sensitization study a prospective generic must run. Granisetron (Sancuso) and selegiline (Emsam) sit behind similar guidances. Yet in every case the Orange Book carries no ANDA, and Drugs.com and GoodRx both list no approved generic for Sancuso, Emsam, or Neupro. The commercial reality is that the addressable market for a weekly rotigotine or granisetron patch is modest, the bioequivalence program is expensive, and the adhesion and sensitization studies carry a real risk of a non-inferiority failure — so no applicant has filed or cleared.

This is the transdermal analogue of the inhaled device-barrier story, but the mechanism differs. For inhalers, the barrier is matching an inhaler device and an aerodynamic particle-size profile. For transdermals, the barrier is matching adhesive performance and skin tolerability closely enough to clear a statistical non-inferiority test on adhesion, irritation, and sensitization — a standard FDA strengthened in its 2016 draft guidance on assessing adhesion with transdermal delivery systems.

What generics do exist, and where the openings are

The 13 generic-available molecules define the substitutable layer of the transdermal market, and they cluster in mature, high-volume products:

• Hormone replacement: estradiol (69 ANDAs across film, system, gel, and emulsion presentations) and testosterone (30 ANDAs, mostly transdermal gels). These two molecules alone account for the bulk of the 231 AB-coded products.
• Analgesia: fentanyl (52 ANDAs — the generic Duragesic matrix patches) and buprenorphine (25 ANDAs — generic Butrans).
• Cardiology and neurology generics: nitroglycerin (20 ANDAs — generic Nitro-Dur), rivastigmine (18 — generic Exelon patch), clonidine (12 — generic Catapres-TTS).
• Established small markets: scopolamine (7 — generic Transderm Scöp), methylphenidate (4 — generic Daytrana), nicotine (3), ethinyl estradiol/norelgestromin (4 — generic Ortho Evra/Xulane), oxybutynin (1).

The pattern mirrors other complex generic routes: generic entry reaches the high-volume, simpler single-molecule patches first and deepest (estradiol, fentanyl, testosterone), and it reaches the newer or lower-volume single-molecule and combination patches last — or, for the four zero-patent neurology and hormone-combination products, not at all. Notably, no transdermal fixed-dose combination molecule (Climara Pro, CombiPatch, Twirla) has a generic at any strength, even where one of the components (estradiol) is the most-genericized molecule in the route.

What this means for launch, formulary, and generic-entry teams

• For formularies, treat the four zero-patent molecules as indefinitely brand-only for planning purposes. Climara Pro, CombiPatch, Sancuso, and Emsam have no listed patents and no ANDA. Do not model automatic substitution or WAC erosion for these based on patent expiry — confirm an AB-coded ANDA exists first, and until one does, assume the brand holds.
• For payer rebate and WAC-erosion modeling, weight the actively marketed on-patent CNS patches (Xelstrym, Secuado, Neupro) to the early-to-mid 2030s and Xelstrym's tail to 2042. These are the transdermal growth layer and will not see generic pressure before their patent estates turn; Adlarity's presentations are discontinued, so it is an absent-generic gap rather than a live brand to model.
• For generic-entry planners, the adhesion/irritation/sensitization bioequivalence bar — not the Orange Book patent column — is the gate. Rotigotine, granisetron, and selegiline each have a published FDA product-specific guidance; the actionable candidates are those with a clear RLD, a non-complex adhesive system, and adequate addressable market to justify the PK + adhesion + sensitization program.
• For launch teams on the brand side, the patent estate is doing real work where it exists (Neupro's 30 patents to 2032, Xelstrym's run to 2042, Secuado's 18 to 2033) but is absent for four molecules. The durable protection for the zero-patent set sits entirely in the formulation-matching bioequivalence barrier and any residual regulatory exclusivity — not in the Orange Book.
• For combination-product regulatory teams, the absence of any generic transdermal fixed-dose combination is the structural opening. No combination patch (hormonal contraceptive, dual-hormone replacement) has an ANDA, despite each having off-patent components; the combination-formulation bioequivalence bar is the common thread.

Sources

• US FDA, Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book), active section, run date June 10, 2026 — products and patents files. Aggregates computed by PharmaDossier from the public Orange Book extract. https://www.accessdata.fda.gov/scripts/cder/ob/default.cfm
• US FDA, "FYs 2013–2017 GDUFA Science and Research Report: Transdermal Drug Products" — bioequivalence, adhesion non-inferiority, irritation and sensitization, and heat-effect requirements for generic transdermal delivery systems. https://www.fda.gov/industry/generic-drug-user-fee-amendments/fys-2013-2017-gdufa-science-and-research-report-transdermal-drug-products
• US FDA, Draft Guidance for Industry, "Assessing Adhesion with Transdermal Delivery Systems and Topical Patches for ANDAs" (2016) — the statistical non-inferiority adhesion standard a generic patch must meet. https://www.fda.gov/media/99949/download
• US FDA, Product-Specific Guidance for rotigotine transdermal system (NDA 021829), recommended June 2012, revised October 2016, October 2018, November 2019 — PK, adhesion, and irritation/sensitization study design. https://www.accessdata.fda.gov/drugsatfda_docs/psg/PSG_021829.pdf
• Complex Generics / GBHI, "Bioequivalence of Transdermal Delivery Systems" — TE = BE + PE principles, product-specific guidance inventory for TDS (buprenorphine, clonidine, estradiol, fentanyl, granisetron, methylphenidate, nitroglycerin, oxybutynin, rivastigmine, rotigotine, scopolamine, selegiline, testosterone). https://www.complexgenerics.org/wp-content/uploads/crcg/prsnt-Luke20180413-GBHI.pdf
• US FDA, Drugs@FDA approval records for single-source transdermal NCEs and combination products (Neupro/rotigotine NDA 021829; Adlarity/donepezil NDA 212304; Xelstrym/dextroamphetamine NDA 215401; Secuado/asenapine NDA 212268; Twirla NDA 204017). https://www.accessdata.fda.gov/scripts/cder/daf/
• Drugs.com, "Generic Sancuso Availability" — no FDA-approved generic granisetron transdermal patch. https://www.drugs.com/availability/generic-sancuso.html
• Drugs.com, "Generic Adlarity Availability" — ADLARITY (donepezil hydrochloride, transdermal system) brand presentations discontinued; no generic approved. https://www.drugs.com/availability/generic-adlarity.html
• Drugs.com, "Neupro FDA Approval History" — rotigotine transdermal approved May 9, 2007 (early Parkinson's) and April 3, 2012 (reformulation for Parkinson's and RLS). https://www.drugs.com/history/neupro.html
• GoodRx, "Sancuso (granisetron)" — no lower-cost generic available. https://www.goodrx.com/sancuso/what-is