Last updated: July 31, 2026
Prometh Plain is a promethazine hydrochloride oral solution used for allergic conditions, nausea and vomiting, motion sickness, and selected perioperative indications. Its active ingredient is an established generic drug rather than a newly developed molecular entity. No product-specific late-stage clinical development program, meaningful patent estate, or standalone public revenue disclosure is evident. Commercial performance is therefore driven by generic availability, supply reliability, prescribing restrictions, formulation economics, and competition from tablets, suppositories, injectable promethazine, antihistamines, and antiemetics.
What is Prometh Plain and what active ingredient does it contain?
Prometh Plain is an oral liquid formulation of promethazine hydrochloride. Promethazine is a phenothiazine derivative with antihistaminic, antiemetic, and sedative properties. Oral solution strengths commonly used in the U.S. include 6.25 mg/5 mL and 12.5 mg/5 mL, although the marketed presentation and labeling must be confirmed against the applicable National Drug Code and manufacturer label.
Promethazine oral solution labeling includes indications for:
- Perennial and seasonal allergic rhinitis
- Allergic conjunctivitis
- Mild uncomplicated allergic skin manifestations
- Motion sickness
- Nausea and vomiting
- Preoperative and postoperative sedation
- Adjunctive use with analgesics in selected settings
The product is not a new chemical entity. FDA approval for promethazine oral solutions relies on the established active ingredient and applicable generic-drug standards rather than a new efficacy program for Prometh Plain as a brand.
What is the FDA regulatory status of Prometh Plain?
Prometh Plain is regulated as a prescription promethazine oral solution. The key regulatory risks are labeling compliance, dosing accuracy, excipient safety, manufacturing quality, and pediatric use.
Promethazine carries a boxed warning concerning respiratory depression and death in children younger than two years of age. The labeling also warns about severe tissue injury from inadvertent injection of promethazine and recommends the deepest available intramuscular route when injection is necessary. Those injection warnings do not eliminate oral-solution risks, including sedation, respiratory depression, impaired driving, and interactions with other central nervous system depressants (FDA, 2023).
The principal FDA considerations are:
| Regulatory issue |
Relevance to Prometh Plain |
| Prescription status |
Prescription drug |
| Active ingredient |
Promethazine hydrochloride |
| Dosage form |
Oral solution or syrup-type liquid |
| Pediatric risk |
Contraindicated in children younger than two years |
| Main safety risks |
Respiratory depression, sedation, anticholinergic effects, overdose |
| Approval pathway |
Generic or established-drug approval framework |
| Product-specific clinical program |
No identifiable major Prometh Plain development program |
| Controlled-substance status |
Promethazine itself is not a federally scheduled controlled substance |
Product-specific status depends on the exact manufacturer, label, and NDC. Promethazine oral solutions can appear under several generic or private-label names, and regulatory status is not interchangeable across manufacturers.
Are there clinical trials for Prometh Plain?
No substantial clinical-trial program dedicated to Prometh Plain as a branded product is identifiable in the public clinical-trial record. Promethazine has extensive historical clinical use, but that evidence base predates modern product-specific trial registration requirements.
ClinicalTrials.gov contains studies involving promethazine in broader clinical contexts, including nausea, vomiting, motion sickness, allergy, sedation, and emergency-care treatment. These studies generally evaluate promethazine as an active ingredient or comparator, not Prometh Plain as a distinct commercial product (ClinicalTrials.gov, 2025).
What does the clinical evidence show for promethazine?
The evidence base supports pharmacologic activity in several established indications, but the product has a narrow modern development profile because:
- Promethazine has been marketed for decades.
- Its clinical utility is well established.
- The main commercial route is generic substitution.
- New trials would rarely create meaningful market exclusivity.
- Safety concerns limit pediatric and sedative use.
The most relevant clinical questions are therefore comparative and safety-focused. These include whether promethazine is preferable to ondansetron for nausea, whether it is appropriate for pediatric allergy symptoms, and how its sedation and anticholinergic effects compare with newer antihistamines.
What patents protect Prometh Plain and promethazine oral solution?
Prometh Plain is unlikely to have meaningful active-ingredient patent protection. Promethazine hydrochloride is an old compound, and any original compound patents would have expired decades ago.
Potential intellectual-property protection could theoretically involve:
- A specific oral-liquid formulation
- Taste-masking technology
- Stabilization or preservative systems
- A dosing device
- A manufacturing process
- A narrowly defined method of use
No major, commercially significant patent estate specifically associated with Prometh Plain is evident from the public profile of promethazine oral solutions. Generic promethazine products typically compete after the expiration of historical compound and use patents.
Does Prometh Plain have Orange Book-listed patents?
Prometh Plain does not appear to have a material Orange Book patent position comparable to a branded new chemical entity. Any Orange Book listing would depend on the exact approved application and sponsor. The FDA Orange Book should be checked by product name, active ingredient, dosage form, and application number because generic promethazine products may have separate approval records (FDA, 2025a).
For a conventional promethazine oral solution, the expected Orange Book position is:
| Orange Book category |
Expected status |
| Active-ingredient patent |
Expired or absent |
| Formulation patent |
No material public estate identified |
| Method-of-use patent |
No material product-specific estate identified |
| Pediatric exclusivity |
Not expected for a mature product |
| New chemical entity exclusivity |
Not applicable |
| Generic substitution |
Available where an AB-rated equivalent exists |
When does Prometh Plain lose exclusivity?
Prometh Plain does not appear to have a meaningful current exclusivity period to lose. The commercial product operates in a mature generic market.
Promethazine oral solution has no expected remaining new-chemical-entity exclusivity, orphan-drug exclusivity, or modern branded exclusivity. Any market protection would arise from manufacturing capacity, distribution contracts, temporary shortages, product quality, or a formulation distinction rather than statutory exclusivity.
What generic entry risks affect Prometh Plain?
Generic-entry risk is high because:
- The active ingredient is old and widely known.
- Promethazine is available in multiple dosage forms.
- Oral solution manufacturing does not require biologic or sterile injectable infrastructure.
- Substitution can occur among therapeutically equivalent products.
- Physicians and pharmacies can shift between suppliers during shortages or price changes.
The main barrier is not patent enforcement. It is the ability to manufacture a stable, palatable, compliant oral liquid at competitive cost and maintain dependable supply.
What is the competitive landscape for Prometh Plain?
Prometh Plain competes in several overlapping markets rather than one single therapeutic segment.
| Competitive segment |
Main alternatives |
Commercial impact |
| Allergy treatment |
Cetirizine, loratadine, fexofenadine, diphenhydramine |
Lower sedation and easier dosing favor newer antihistamines |
| Nausea and vomiting |
Ondansetron, metoclopramide, prochlorperazine |
Clinical setting and adverse-effect profile determine selection |
| Motion sickness |
Meclizine, dimenhydrinate, scopolamine |
Promethazine competes on familiarity and efficacy |
| Pediatric liquid therapy |
Diphenhydramine, cetirizine, ondansetron liquids |
Safety warnings constrain promethazine use |
| Sedation |
Hydroxyzine, benzodiazepines, other sedatives |
Promethazine is generally an adjunct rather than a primary modern sedative |
| Promethazine dosage forms |
Tablets, suppositories, injectable products |
Tablets may have lower manufacturing and shipping costs |
Promethazine retains demand where clinicians value broad activity, low acquisition cost, and liquid administration. It is less competitive when reduced sedation, modern pediatric positioning, or specialized antiemetic efficacy is prioritized.
How strong is the patent estate for Prometh Plain?
The patent estate is weak from a branded-product perspective. The product’s commercial defensibility depends more on execution than on exclusionary rights.
Manufacturing and formulation barriers
The principal technical barriers include:
- Maintaining assay uniformity throughout the bottle
- Controlling degradation and discoloration
- Preserving chemical stability
- Managing microbial limits
- Producing an acceptable taste profile
- Ensuring accurate dosing with household or supplied devices
- Complying with excipient and labeling requirements
- Avoiding manufacturing interruptions
These are operational barriers, not durable exclusivity barriers. A competitor with an approved equivalent and reliable supply can generally enter without overcoming a complex patent platform.
Geographic coverage
Promethazine oral solutions are sold in multiple jurisdictions, but regulatory status differs by country. The United States relies on FDA approval and Orange Book substitution standards. European markets apply national or centralized regulatory procedures depending on the product and jurisdiction. Patent and data-exclusivity analysis must therefore be conducted separately for the United States, European Union, United Kingdom, Canada, and other markets.
The active ingredient’s age makes broad global composition-of-matter protection unlikely. Local market access is more likely to depend on registration, local manufacturing, pricing, reimbursement, and pharmacovigilance requirements.
Which companies are challenging Prometh Plain?
No major Paragraph IV litigation campaign directed specifically at Prometh Plain is evident from the public profile of this mature product. Promethazine oral solution is more likely to face ordinary generic competition than a branded challenge involving a live patent estate.
What is the Paragraph IV risk?
Paragraph IV risk is low in the conventional branded-patent sense because there is no apparent commercially important patent barrier. The greater risk is substitution by other approved promethazine oral solutions or by alternative antiemetic and antihistamine products.
A Paragraph IV filing would matter only if a sponsor held an unexpired, listed patent covering the exact product, formulation, or approved use. That scenario is not the expected market structure for a standard promethazine oral solution.
Are there licensing deals or settlement agreements involving Prometh Plain?
No prominent public licensing transaction or patent settlement involving Prometh Plain is evident. Mature generic oral liquids are commonly supplied through manufacturer, distributor, pharmacy, hospital, and private-label arrangements rather than high-value intellectual-property licenses.
Commercial agreements may still exist at the manufacturer or distributor level, but they are not generally disclosed in a way that permits reliable product-level valuation.
What is the market outlook for Prometh Plain from 2025 to 2030?
The base-case outlook is stable to modestly declining unit demand, with revenue determined by price and supply conditions rather than clinical expansion.
| Scenario |
2025-2030 outlook |
Main drivers |
| Base case |
Flat to low-single-digit annual revenue change |
Mature demand, generic pricing, stable prescriptions |
| Upside case |
Low- to mid-single-digit growth |
Competitor shortages, stronger liquid-dose demand, distribution expansion |
| Downside case |
Mid-single-digit decline or greater |
Price erosion, supplier exit, safety-driven prescribing reduction, substitution by ondansetron or newer antihistamines |
Revenue exposure
Product-level revenue for Prometh Plain is not publicly disclosed. The addressable market is the broader promethazine oral-solution category, not a protected Prometh Plain franchise. Revenue concentration is likely to be highest in:
- Retail and specialty pharmacies
- Emergency departments
- Outpatient clinics
- Long-term-care facilities
- Pediatric and family-practice settings
- Distributors supplying low-cost prescription liquids
Growth is constrained by the mature generic structure. A manufacturer could improve revenue through reliable supply, improved packaging, institutional contracts, and geographic expansion, but those gains would not create durable pricing power.
Generic launch scenarios
A new generic entrant could launch through an abbreviated new drug application if it demonstrates pharmaceutical equivalence, bioequivalence where required, and compliance with FDA manufacturing standards. The likely market effects are:
- Initial price competition among approved liquid suppliers.
- Pharmacy substitution toward lower-cost or preferred products.
- Contract renegotiation by wholesalers and health systems.
- Greater volatility if one or more manufacturers experience shortages.
- Reduced share for a branded or private-label product without a formulation advantage.
The strongest commercial position would belong to a supplier with multiple manufacturing sites, an established liquid-dose portfolio, and broad pharmacy distribution.
What litigation or regulatory events could change the outlook?
The principal risks are regulatory and operational rather than patent-based.
Potential value-changing events include:
- FDA inspection findings
- Product recalls
- Manufacturing-site disruptions
- Microbial contamination
- Labeling revisions involving pediatric or respiratory risk
- A shortage affecting competing suppliers
- New clinical guidance favoring alternative antiemetics
- Pricing pressure from additional ANDA approvals
- Distribution termination or private-label delisting
A new patent dispute would be less likely to alter the market unless it involved a genuinely differentiated formulation or delivery system.
Key Takeaways
- Prometh Plain is a promethazine hydrochloride oral-solution product in a mature generic market.
- No major Prometh Plain-specific clinical-trial program is evident.
- Promethazine has extensive historical clinical use, but modern product-specific development is limited.
- No material active patent estate or new-drug exclusivity position is apparent.
- Paragraph IV and branded patent-litigation risk are low relative to ordinary generic substitution risk.
- The main commercial advantages are supply reliability, liquid-dose convenience, distribution, and competitive pricing.
- The base-case 2025-2030 outlook is stable to modestly declining, with upside mainly tied to competitor shortages or distribution gains.
- Pediatric respiratory-depression warnings and sedation limit expansion into some patient populations.
- Manufacturing quality, formulation stability, taste, and dosing accuracy are the main technical barriers.
FAQs
Is Prometh Plain the same as promethazine syrup?
Prometh Plain is a brand or product designation associated with promethazine hydrochloride oral solution. Equivalence depends on the exact strength, formulation, approved labeling, and FDA therapeutic-equivalence status.
Does Prometh Plain contain codeine?
Prometh Plain refers to a plain promethazine formulation and should not be assumed to contain codeine. Promethazine-codeine products are separate formulations with different labeling, regulatory controls, and safety risks.
Can Prometh Plain be substituted with promethazine tablets?
Substitution depends on the prescribed dosage form, strength, patient needs, pharmacy rules, and the prescriber’s instructions. Oral solution and tablets contain the same active ingredient but are not interchangeable on a volume-to-tablet basis without dose conversion.
Is Prometh Plain suitable for children?
Promethazine is contraindicated in children younger than two years because of the risk of fatal respiratory depression. Use in older children remains subject to age, weight, indication, dose, sedation risk, and approved labeling.
Does Prometh Plain have biosimilar competition?
No. Promethazine is a small-molecule drug, not a biologic. It competes with generic equivalents and alternative small-molecule therapies rather than biosimilars.
References
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ClinicalTrials.gov. (2025). Search results for promethazine. U.S. National Library of Medicine. https://clinicaltrials.gov/search?term=promethazine
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U.S. Food and Drug Administration. (2023). Promethazine hydrochloride oral solution prescribing information. FDA. https://www.accessdata.fda.gov/
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U.S. Food and Drug Administration. (2025a). Approved drug products with therapeutic equivalence evaluations. FDA. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files
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U.S. Food and Drug Administration. (2025b). Drugs@FDA: FDA-approved drugs database. FDA. https://www.accessdata.fda.gov/scripts/cder/daf/
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U.S. National Library of Medicine. (2025). DailyMed: Promethazine hydrochloride drug labels. https://dailymed.nlm.nih.gov/dailymed/search.cfm?query=promethazine%20hydrochloride
