Diphenhydramine clinical trials
Diphenhydramine is named as an intervention in 10 current clinical trials in our China, Israel, USA, France, Spain, Italy, Brazil, Poland, Japan, UK, Germany, Sweden, Czechia, Turkey, Canada, Australia, Denmark, Norway, Ireland, South Korea, Mexico, Taiwan, Portugal and Netherlands registers. 2 are recruiting patients now. The most common phase is Phase 3. The sponsor with the most trials is Sanofi (4). The most-studied condition is Plasma Cell Myeloma. The EU clinical trials register (CTIS) separately lists 3 authorised or ongoing trials.
Where Diphenhydramine is approved
All regulators →Of the three regulators tracked here, the first to approve Diphenhydramine was the US, on 4 Mar 1946.
From the regulators' own registers: FDA Drugs@FDA, the EMA medicines list and Health Canada's Notice of Compliance database. Dates are the first listed approval of a product containing only this substance; combination products and nationally authorised EU medicines are not counted.
What health systems spend on Diphenhydramine
All medicines →From NHSBSA Prescription Cost Analysis (Open Government Licence v3.0) and CMS State Drug Utilization Data. Both are gross amounts: neither system publishes its discounts or rebates per drug. Products combining several substances are not counted here.
How Diphenhydramine works
All drug targets →- Histamine H1 receptor antagonist AntagonistTarget: HRH1 histamine receptor H1✓ In ChEMBL and the Guide to Pharmacology
- HeadachePhase 3
- Common coldPhase 3
- Migraine disorderPhase 3
- Non-small cell lung carcinomaPhase 3
- Oral mucositisPhase 3
- UrticariaPhase 3
- Breast cancerPhase 2/3
- Ovarian cancerPhase 2/3
- Cluster headachePhase 2
- Recurrent aphthous stomatitisPhase 2
Mechanisms and diseases from ChEMBL via the Open Targets Platform (release 26.09), ChEMBL record CHEMBL657, CC BY-SA 3.0. Targets checked against the IUPHAR/BPS Guide to PHARMACOLOGY (2026.3.1), ligand 1224, CC BY-SA 4.0. Trial phases are not approvals: approved uses are shown from the regulators' own records where we hold them.
Patient leaflets for Diphenhydramine
The package leaflet is the official guide for patients that comes with every medicine. These links go to the regulators that publish it.
- IEIreland: 1 product on the HPRA listEach product record links to the HPRA, which publishes the leaflet and SmPC.
- UKUnited Kingdom: Search MHRA ProductsPatient information leaflets and SmPCs for UK-licensed products.
- USUnited States: Search DailyMedFDA-approved labels, including patient and medication guides.
Leaflets differ between brands and countries; always read the one that comes with your own medicine. This is regulatory information, not medical advice.
Reference identifiers for Diphenhydramine
- ChEMBL
- CHEMBL657
- DrugBank
- DB01075
- PubChem CID
- 3100
- CAS number
- 58-73-1
- FDA UNII
- 8GTS82S83M
- Wikidata
- Q413486
- Wikipedia
- Diphenhydramine
Codes that identify this medicine in other databases, from Wikidata (CC0), matched by its ChEMBL ID. The ATC code is the WHO classification of what the medicine is used for.
Trials by status
Trials by phase
Clinical trials of Diphenhydramine
10 trialsRegisters list studies that are recruiting, about to open, active but closed to enrolment, or enrolling by invitation. The UK and USA registers cover industry-sponsored studies only. Trial titles and statuses are copied from the registry as published.
Diphenhydramine in the EU trials register (CTIS)
3 trialsAuthorised or ongoing trials in the EU Clinical Trials Information System that list a product containing Diphenhydramine. Many trials are registered in both CTIS and ClinicalTrials.gov, so these are shown separately rather than added to the count above. Trials with a site in Ireland are listed first.
Diphenhydramine across our data
Ireland · EU · USThe same active substance in our other registers, matched by its exact name. Each entry links to the register record it comes from.
Licensed in Ireland (HPRA)
1 single-substance product containing Diphenhydramine on the HPRA medicines list.
- Nytol One-A-Night 50 mg TabletsChefaro Ireland DAC, · PA1186/016/001 · Marketed
Supply shortages
No entry for Diphenhydramine in the EMA, FDA or German BfArM shortage lists we track.
Conditions studied with Diphenhydramine
12 conditionsSponsors
lead sponsor per trial| Lead sponsor | Trials |
|---|---|
| Sanofi | 4 |
| Hoffmann-La Roche | 2 |
| Tianjin Medical University Cancer Institute and Hospital | 2 |
| Merck Sharp & Dohme LLC | 2 |
By country register
A trial with sites in more than one country appears in each of those registers. CTIS does not publish a recruiting flag; its trials may also appear in the registers above.
Related compounds
Questions about Diphenhydramine trials
How many clinical trials are testing Diphenhydramine?
10 current trials in our China, Israel, USA, France, Spain, Italy, Brazil, Poland, Japan, UK, Germany, Sweden, Czechia, Turkey, Canada, Australia, Denmark, Norway, Ireland, South Korea, Mexico, Taiwan, Portugal and Netherlands registers name Diphenhydramine as a drug or biological intervention, as of the registry sync on 9 November 2026. Completed and withdrawn studies are not counted.
Are Diphenhydramine trials recruiting patients?
Yes. 2 of the 10 trials are recruiting: 2 with sites in Israel, 1 with sites in France, 1 with sites in Spain, 1 with sites in Italy, 1 with sites in Japan, 1 with sites in Sweden, 1 with sites in Canada, 1 with sites in Denmark and 1 with sites in Netherlands. Eligibility and site contacts are on each trial's record. Only the study team can confirm whether a patient is eligible.
Who sponsors Diphenhydramine clinical trials?
Sanofi (4), Hoffmann-La Roche (2), Tianjin Medical University Cancer Institute and Hospital (2) and Merck Sharp & Dohme LLC (2). The number in brackets is how many trials each organisation leads.
Are there Diphenhydramine clinical trials in Ireland?
Yes. 1 trial in our Ireland register (ClinicalTrials.gov). Some may be the same study registered in both. See the Irish clinical trials register for sites and contacts.
Is Diphenhydramine licensed in Ireland?
Yes. The HPRA medicines list includes 1 single-substance product containing Diphenhydramine, for example Nytol One-A-Night 50 mg Tablets (Chefaro Ireland DAC,). A licence does not mean a product is currently marketed or reimbursed; see each product's record.
Is there a Diphenhydramine shortage?
Not in the lists we track: Diphenhydramine has no entry in the EMA, FDA or German BfArM shortage registers as of their latest sync.
Where does this information come from?
Every trial, status, phase and sponsor on this page is copied from public ClinicalTrials.gov records by a daily sync. Nothing here describes how Diphenhydramine works or whether it is effective, and it is not medical advice.
How this page is built
Everything on this page is copied from public ClinicalTrials.gov registry records — it is not written from memory, and nothing here describes how Diphenhydramine works or whether it is effective. Each trial links to its own record so you can check it yourself.
- ClinicalTrials.gov (U.S. National Library of Medicine) ↗ Trial IDs, titles, intervention names and synonyms, phase, overall status, lead sponsor and conditions for every trial on this page
This page is built automatically: a daily sync job reads the registry records behind our country trial registers, collects every trial that lists Diphenhydramine (or a registered synonym) as a drug or biological intervention, and tabulates the registry fields directly. Placebos and generic comparators are excluded. There is no AI drafting and no per-compound editorial pass, and the page has not been clinically reviewed. The “last verified” date above is the timestamp of that sync, not a review date. Our general editorial approach is described in our editorial standards and corrections policy. The ClinicalTrials.gov data on this page was last retrieved on 9 Nov 2026. How every register is built: methodology · fixes we have made: corrections log.