Last updated: July 28, 2026
Phenergan (promethazine) clinical trials update, market analysis and launch exclusivity projection
Phenergan is a brand of promethazine, a first-generation antihistamine used for allergic symptoms and off-label antiemetic and sedative indications. Commercially, Phenergan sits in a mature, low-price generic environment across key geographies, with limited scope for new regulatory exclusivity. Clinical-trial activity is sporadic and typically academic or small, because promethazine is off-patent in most major markets and is widely available as generics.
What clinical trials have been conducted for Phenergan (promethazine) and what’s the latest status?
Featured snippet answer: Current clinical-trial activity for promethazine is mostly small, investigator-led studies or comparative studies where promethazine is an established comparator, not an investigational new drug with brand-level development.
Which indications show the most ongoing or recent promethazine trial activity?
Promethazine trial activity most commonly clusters around:
- Postoperative or acute nausea and vomiting (antiemetic comparator roles)
- Motion sickness and migraine-associated nausea
- Sedation or premedication protocols in specific settings
- Allergic rhinitis or urticaria symptom control (often as an antihistamine comparator)
- Breakthrough pain or emergency department antiemetic regimens (comparative arms)
How to interpret trial “updates” for an established drug like promethazine
Because Phenergan/promethazine is widely generic, “updates” often mean:
- Registry entries with limited enrollment sizes
- Trial completion without major regulatory endpoints
- Trials evaluating real-world protocols rather than novel formulations or new chemical entities
How many Phenergan-specific trials exist versus generic promethazine trials?
Most registry searches capture “promethazine” rather than “Phenergan.” In practice, branded and generic promethazine are pharmacologically equivalent for standard endpoints, so trial counts under the brand name typically understate total evidence. For a market analysis, the practical feedstock is promethazine trial activity rather than brand-specific studies.
What is the current FDA regulatory status of Phenergan (promethazine) and what does Orange Book show?
Featured snippet answer: Phenergan (promethazine) is marketed under an FDA-approved New Drug Application for which active ingredient coverage is largely expired, with many generic approvals. Orange Book listings for promethazine antiallergy/antiemetic products generally reflect limited remaining patent-protected claims.
Is Phenergan listed in the Orange Book?
Orange Book coverage depends on the specific dosage form and strength (e.g., oral tablets/syrup, injectable solutions, suppositories). For established antihistamine brands, Orange Book listings typically show the original NDA plus many abbreviated approvals for generics and labeled versions. Patent listings, where present, tend to be minimal or already expired.
Which product strengths and dosage forms materially affect regulatory and patent position?
For market and launch risk, the relevant buckets are:
- Oral immediate-release formulations (tablets, syrup)
- Injectable (IM/IV labeling varies by product)
- Rectal suppositories (where marketed)
What patents protect promethazine/Phenergan and how strong is the remaining patent estate?
Featured snippet answer: Patent protection for promethazine as an active ingredient is largely exhausted in major markets, with any remaining IP focused on narrow formulation, packaging, method-of-use, or process claims for specific dosage forms.
What patent types still matter for an old antihistamine brand?
For an off-patent molecule, remaining IP tends to be claim-sliced into:
- Method-of-use patents tied to specific dosing regimens for nausea and vomiting
- Formulation patents for controlled release or stability-focused composition tweaks
- Manufacturing process patents for sterile production, if applicable
- Labeling-related exclusivity, if any, tied to specific indications (rare for a widely generic molecule)
How to map the estate to actual competitive barriers
- If no active formulation or method-of-use patents remain, generics can launch without Paragraph IV leverage.
- If narrow patents exist for specific dosage forms, the competitive risk concentrates on those forms and label indications.
When does Phenergan lose exclusivity and what are the likely generic entry risks?
Featured snippet answer: Phenergan has effectively lost regulatory exclusivity in most jurisdictions. Competitive pressure is dominated by generic pricing and supply, not by exclusivity expiration.
Paragraph IV exposure: expected baseline for mature promethazine
For off-patent antihistamines, there is typically no meaningful Paragraph IV campaign tied to the original molecule. Generic manufacturers generally enter through:
- FDA ANDA approvals against already genericized reference listed drug labeling
- Shared reliance on older bridging studies and published pharmacology for established indications
- New line extensions (different strengths/dosage forms) rather than “challenger” IP fights
Biosimilar risk
Not applicable. Promethazine is a small molecule.
How does Phenergan compare with other promethazine antiemetic and antihistamine products in the market?
Featured snippet answer: Competitive substitutes include other first-generation antihistamines (e.g., diphenhydramine) and dedicated antiemetics used in nausea and vomiting pathways (e.g., metoclopramide, ondansetron, prochlorperazine), depending on clinical setting.
Indication-driven substitution patterns
- Emergency department nausea protocols often favor newer antiemetics for efficacy and tolerability, with promethazine as a lower-cost alternative in some pathways.
- Allergy symptom control often shifts to second-generation antihistamines due to side-effect profile, keeping promethazine demand more niche.
Pricing and tender dynamics
In most markets, promethazine competes primarily on:
- Wholesale acquisition cost and tender pricing
- Supply continuity for injectable products
- Formulary status and hospital purchasing contracts
What is the Phenergan market size, revenue exposure, and growth outlook?
Featured snippet answer: The promethazine market is mature and price-sensitive; growth is driven by volume stability, intermittent supply demand, and hospital formulary churn rather than brand-level premium.
Market revenue drivers
- Short-cycle purchasing: hospital and wholesale orders respond to acute care protocols
- Generic substitution: brand premium is limited
- Dosage form mix: injectable versus oral mix can shift by procurement and clinical practice
Downside and upside levers
Downside:
- Continued generic pricing pressure
- Formulary preference shift toward non-sedating antihistamines and modern antiemetics
- Safety-related label scrutiny for sedation and adverse CNS effects
Upside:
- Renewed use in specific antiemetic protocols
- Supply constraints in certain generics can temporarily lift market pricing
- Geographic tender cycles favoring older, low-cost options
Forecast style for an off-patent antihistamine
A reasonable projection framework for promethazine looks like:
- Flat-to-low single-digit CAGR driven by population and acute care utilization
- Price erosion dominating nominal growth
- Any brand-relevant growth is typically captured by share gains in tenders, not by IP-backed premium
What clinical outcomes matter most for promethazine’s continued use and what safety signals influence adoption?
Featured snippet answer: Key clinical decision drivers are efficacy for nausea control, sedative burden, and risk of adverse effects such as respiratory depression and anticholinergic CNS effects depending on route and population.
Safety considerations that affect formulary adoption
- Sedation and cognitive impairment risk
- Anticholinergic effects (e.g., dry mouth, urinary retention risk)
- Injection-associated safety considerations and administration technique
- Pediatric safety: promethazine has historically had strong warnings in children, which reduces eligible populations and shapes dosing protocols
Evidence pattern
For established agents, the evidence base often emphasizes:
- Comparative clinical effectiveness in nausea pathways
- Safety profile in specific subgroups
- Practical outcomes like time-to-symptom relief in emergency or perioperative settings
What manufacturing and supply constraints affect Phenergan/promethazine availability?
Featured snippet answer: Availability risks for generics tend to come from sterile manufacturing capacity, cold chain or stability requirements, and quality system performance rather than from active pharmaceutical ingredient supply alone.
Dosage forms most exposed to supply volatility
- Injectable presentations are more exposed due to sterile manufacturing oversight and batch release bottlenecks.
- Oral syrups may be exposed to excipient supply constraints and stability shelf-life limits.
Market impact from shortages
Shortages usually produce short-duration:
- Price spikes
- Switching to alternative generics or therapeutic substitutes
- Accelerated use of alternative antiemetics
How does Phenergan compete against modern antiemetics and antihistamines?
Featured snippet answer: Modern antiemetics and second-generation antihistamines reduce promethazine’s share in many settings, but promethazine remains a cost-controlled option where formularies allow sedating agents or where alternative coverage is limited.
Comparative positioning by clinical setting
- Postoperative nausea: often dominated by 5-HT3 antagonists, neurokinin-1 antagonists, and multimodal pathways; promethazine competes on cost and protocol familiarity.
- ED nausea: ondansetron/prochlorperazine/metoclopramide can displace promethazine based on local guidelines and contraindications.
- Allergic rhinitis/urticaria: second-generation antihistamines reduce promethazine’s routine use; promethazine persists where sedation is acceptable or where cost constraints dominate.
Key Takeaways
- Phenergan is promethazine, an off-patent small molecule with limited brand-level exclusivity and no material biosimilar pathway.
- Clinical-trial updates for promethazine are typically small, comparative, or investigator-led; they rarely re-shape regulatory status.
- Market dynamics are dominated by generic pricing, formulary decisions, and supply continuity, not by expiration-driven generic entry fights.
- Any remaining IP, if present, is narrow and likely dosage-form or method-of-use specific; however, the baseline expectation is extensive generic availability.
FAQs
What are the most common uses of Phenergan (promethazine) in clinical practice?
Promethazine is used for allergic symptoms and has long-standing use as an antiemetic and sedative in many protocols, with specific labeling and age restrictions varying by jurisdiction.
Is Phenergan used for postoperative nausea and vomiting (PONV)?
It can be used as an antiemetic option within multimodal regimens, but modern antiemetics often drive first-line selection depending on institutional guideline.
What is the difference between Phenergan brand promethazine and generic promethazine products?
They share the same active ingredient, route, and labeled dosing but may differ in excipients, formulation stability, and manufacturing quality controls.
Are there any ongoing promethazine clinical trials targeting pediatric indications?
Pediatric development is constrained by historical safety warnings and typical regulatory caution; trials are more common in adult or protocol-restricted contexts.
What happens to promethazine supply and pricing during generic shortages?
Shortages generally cause temporary price increases and formulary switching to alternative antiemetics or alternative strengths/dosage forms until supply stabilizes.
References
- FDA Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations (accessed via FDA database).
- ClinicalTrials.gov (search results for promethazine).
