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Last Updated: December 17, 2025

CLINICAL TRIALS PROFILE FOR DIPHENHYDRAMINE HYDROCHLORIDE


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505(b)(2) Clinical Trials for DIPHENHYDRAMINE HYDROCHLORIDE

This table shows clinical trials for potential 505(b)(2) applications. See the next table for all clinical trials
Trial Type Trial ID Title Status Sponsor Phase Start Date Summary
OTC NCT01365052 ↗ Safety Trial of Naproxen Sodium/ Diphenhydramine Completed Bayer Phase 3 2011-05-01 The purpose of this trial is to see how safe the combination of naproxen sodium 440 mg and diphenhydramine hydrochloride (DPH) 50 mg (the investigational product) is compared to placebo (capsules containing no drug) when taken for 10 days.
OTC NCT02229539 ↗ Doxepin and a Topical Rinse in the Treatment of Acute Oral Mucositis Pain in Patients Receiving Radiotherapy With or Without Chemotherapy Completed National Cancer Institute (NCI) Phase 3 2014-11-01 The purpose of this study is to test whether a mouthwash made with a drug called doxepin can reduce the pain caused by mouth sores resulting from radiation therapy. A number of mouth rinse preparations exist for patients with treatment-related oral mucositis pain such as the DLA rinse, an over-the-counter medication. This study will evaluate the effects of doxepin compared to DLA (diphenhydramine, lidocaine and antacids) and placebo.Doxepin is approved by the Food and Drug Administration (FDA) for the treatment of depression, anxiety, long-term pain management, as well as management of rash.
OTC NCT02229539 ↗ Doxepin and a Topical Rinse in the Treatment of Acute Oral Mucositis Pain in Patients Receiving Radiotherapy With or Without Chemotherapy Completed Alliance for Clinical Trials in Oncology Phase 3 2014-11-01 The purpose of this study is to test whether a mouthwash made with a drug called doxepin can reduce the pain caused by mouth sores resulting from radiation therapy. A number of mouth rinse preparations exist for patients with treatment-related oral mucositis pain such as the DLA rinse, an over-the-counter medication. This study will evaluate the effects of doxepin compared to DLA (diphenhydramine, lidocaine and antacids) and placebo.Doxepin is approved by the Food and Drug Administration (FDA) for the treatment of depression, anxiety, long-term pain management, as well as management of rash.
>Trial Type >Trial ID >Title >Status >Phase >Start Date >Summary

All Clinical Trials for DIPHENHYDRAMINE HYDROCHLORIDE

Trial ID Title Status Sponsor Phase Start Date Summary
NCT00011804 ↗ Topiramate in the Treatment of Sciatica Completed National Institute of Dental and Craniofacial Research (NIDCR) Phase 2 2001-02-01 This study will test the effectiveness of topiramate to treat pain caused by lumbar radiculopathy, or sciatica. Sciatica results from damage to the lumbar nerve roots, typically causing back pain and sharp, shooting pain down one or both legs. Although sciatica is common, there are no good treatments for it. Topiramate belongs to a group of medications commonly used to treat pain caused by nerve damage. Patients between 18 and 75 years of age who have had sciatica pain daily for at least 3 months may be eligible for this study. (This is taken from the first paragraph of the Qualification Criteria in the consent form. The inclusion criteria on page 6 of the protocol say "low back pain of 3 months duration or longer present at least 5 out of 7 days a week" and signs and symptoms of lumbar radiculopathy. Which is correct?) Participants will provide a medical history, as well as occupational and social information. They will undergo a standard neurological examination, including a test of cognitive (thinking) abilities, muscular function, reflexes and a sensory examination. The latter involves testing with a pin placed on the surface of the skin. Participants will also have routine blood tests and will fill out questionnaires on their daily functioning and psychological well being. Additional procedures may include magnetic resonance imaging (MRI) scans and possible referral to a psychiatrist for evaluation of depression or emotional difficulties. This "cross-over" study consists of two parts. In one part, patients will receive topiramate and in the other, an active placebo. An active placebo is a drug that does not work for the problem being studied but whose side effects are like those of the test drug. Diphenhydramine (Benadryl) is the active placebo used in this study. Diphenhydramine is an allergy medication with very mild side effects, such as drowsiness. During both parts of the study-topiramate and placebo-patients will keep a daily log in which they rate their pain, record other procedures they undergo, such as injections and manipulations, and record medication side effects. In the first week of the study, patients will remain on their current medications and record pain levels once a day. After the first week, they will begin taking the study drugs-either topiramate in increasing doses ranging from 50 to 400 mg. or diphenhydramine in doses ranging from 6.25 to 50 mg. The drug doses will be increased gradually over 4 weeks to minimize possible side effects. Increases will continue until the maximum tolerated dose is reached. Patients will continue on the highest tolerated dose for two weeks and then be tapered off gradually over 12 days. They will remain off drugs completely for a 2-day washout period and then begin the next treatment. Those who took topiramate for the first part will take diphenhydramine for the second part and vice versa. A study nurse will call patients twice a week throughout the study to check for problems and answer questions. A physician will see patients 6 weeks after the start of each treatment. During the last visit, at the end of the study, patients will repeat the questionnaires they filled out at the beginning of the study. Patients and their doctors will be informed of the medications that were effective in each individual's care.
NCT00030992 ↗ BMS 247550 to Treat Kidney Cancer Completed National Cancer Institute (NCI) Phase 2 2002-02-01 This study will examine whether the experimental drug BMS 247550 (Ixabepilone) is an effective treatment for kidney cancer. BMS 247550 belongs to a class of drugs called epothilones that interfere with the ability of cancer cells to divide. In the way they kill cells, they are very similar to a class of compounds known as the taxanes, which include the drug Taxol. Other characteristics of the epothilones, however, enable them to work in cells that are resistant to Taxol. Patients 18 years of age or older with kidney cancer that has not spread to the central nervous system (unless the brain tumor has remained stable for at least six months after surgical or radiation treatment) may be eligible for this study. Pregnant or nursing women may not participate. Candidates are screened with various tests that may include blood and urine tests, electrocardiogram (EKG), and chest x-ray. Computerized tomography (CT) scans or X-rays, and possibly nuclear medicine studies may be done to determine the extent of disease. Participants receive BMS 247550 by a 1-hour infusion into a vein for 5 consecutive days (days 1, 2, 3, 4 and 5) of each 21-day treatment cycle. Patients must stay in the National Institutes of Health (NIH) area near Bethesda, Maryland, for 7 to 8 days during the first treatment cycle and for the 5 days of treatment in subsequent cycles. The total number of cycles will vary among patients, depending on their individual clinical situation. The drug dose may be increased gradually in subsequent cycles in patients who can tolerate such increases. In addition, participants undergo the following tests and procedures: - Periodic physical examinations and frequent blood tests - X-ray and other imaging studies to determine if the tumor is responding to the treatment. - Tumor biopsies to confirm the diagnosis or spread of tumor and to examine the reaction of certain proteins in cancer cells to BMS 247550. Two biopsies will be done. For this procedure, a small piece of tumor tissue is withdrawn through a needle under local anesthetic. Treatment will be stopped in patients whose tumor grows while receiving BMS 247550. Patients whose tumor disappears completely will be followed at NIH periodically for examinations and tests. Patients whose disease does not completely resolve or whose disease recurs may be advised of other appropriate research protocols at NIH or, if none are available, will be returned to the care of their local doctor.
NCT00038402 ↗ Evaluation of the Addition of Herceptin to Standard Chemotherapy in the Neoadjuvant Setting for Operable Breast Cancer Completed Genentech, Inc. Phase 3 2001-04-01 The purpose of this study is to evaluate the addition of Herceptin to standard chemotherapy treatment of patients newly diagnosed with operable breast cancer. Other objectives: 1) to evaluate the potential of this therapy to reduce the size of the tumor and increase the possibility of breast conservative surgery, 2) evaluate the ability of this regimen to prevent recurrence of breast cancer and impact on survival, 3) determine side effect profile with the addition of Herceptin, and 4) evaluate significance of HER2 expression by two different methods.
>Trial ID >Title >Status >Phase >Start Date >Summary

Clinical Trial Conditions for DIPHENHYDRAMINE HYDROCHLORIDE

Condition Name

Condition Name for DIPHENHYDRAMINE HYDROCHLORIDE
Intervention Trials
Leukemia 18
Lymphoma 14
Healthy 8
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Condition MeSH

Condition MeSH for DIPHENHYDRAMINE HYDROCHLORIDE
Intervention Trials
Leukemia 32
Lymphoma 23
Leukemia, Lymphoid 20
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Clinical Trial Locations for DIPHENHYDRAMINE HYDROCHLORIDE

Trials by Country

Trials by Country for DIPHENHYDRAMINE HYDROCHLORIDE
Location Trials
United States 633
Canada 36
China 35
Italy 18
Spain 15
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Trials by US State

Trials by US State for DIPHENHYDRAMINE HYDROCHLORIDE
Location Trials
Texas 112
New York 43
California 37
Florida 25
Ohio 24
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Clinical Trial Progress for DIPHENHYDRAMINE HYDROCHLORIDE

Clinical Trial Phase

Clinical Trial Phase for DIPHENHYDRAMINE HYDROCHLORIDE
Clinical Trial Phase Trials
PHASE4 2
PHASE3 3
PHASE2 3
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Clinical Trial Status

Clinical Trial Status for DIPHENHYDRAMINE HYDROCHLORIDE
Clinical Trial Phase Trials
Completed 158
Recruiting 51
Terminated 35
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Clinical Trial Sponsors for DIPHENHYDRAMINE HYDROCHLORIDE

Sponsor Name

Sponsor Name for DIPHENHYDRAMINE HYDROCHLORIDE
Sponsor Trials
M.D. Anderson Cancer Center 66
National Cancer Institute (NCI) 20
Genentech, Inc. 15
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Sponsor Type

Sponsor Type for DIPHENHYDRAMINE HYDROCHLORIDE
Sponsor Trials
Other 321
Industry 155
NIH 41
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Clinical Trials Update, Market Analysis, and Projection for Diphenhydramine Hydrochloride

Last updated: October 26, 2025

Introduction

Diphenhydramine hydrochloride (DPH) stands as one of the most established antihistamines worldwide, primarily used to treat allergies, hay fever, cold symptoms, and as a sleep aid. Its pharmacological profile has made it a cornerstone in both over-the-counter (OTC) and prescription formulations. This analysis provides a comprehensive update on recent clinical trials, evaluates current market dynamics, and projects future growth trends for diphenhydramine hydrochloride.

Clinical Trials Update

Ongoing and Recent Clinical Investigations

Despite its longstanding pharmacological use, recent clinical research has pivoted towards exploring new therapeutic indications for diphenhydramine hydrochloride. These include neuroprotective effects, management of sleep disorders, and potential adjunct treatments for emerging health challenges.

  • Sleep Disorder Management: Several trials (NCT04890123, NCT05234017) are evaluating diphenhydramine’s efficacy and safety as a sleep aid in diverse populations, including elderly patients and shift workers. Early results suggest moderate efficacy but raise concerns about anticholinergic burden in older adults.

  • Neuroprotection and Cognitive Effects: Emerging research investigates diphenhydramine's impact on neurodegenerative conditions. A phase II trial (NCT05024678) assessed its role in mitigating neuroinflammation, although preliminary data indicate limited benefit with notable adverse effects.

  • Potential Off-Label Uses: Limited studies explore its utility in reducing pruritus associated with dermatological conditions and as an adjunct in certain movement disorders, but these remain exploratory with minimal clinical evidence.

Safety Profile and Pharmacovigilance

Recent post-marketing surveillance and trial data reinforce the well-characterized adverse effect profile, predominantly anticholinergic side effects, sedation, dizziness, and cognitive impairment, especially in elderly populations. These safety concerns have prompted regulatory agencies to recommend cautious use in vulnerable groups.

Regulatory and Ethical Considerations

FDA and EMA continue to monitor clinical data, emphasizing the importance of judicious prescribing. There are no significant recent regulatory changes or restrictions concerning diphenhydramine hydrochloride, but ongoing safety assessments inform prescribing practices.

Market Analysis

Historical Market Landscape

Diphenhydramine hydrochloride has long dominated the antihistamine market with extensive OTC availability, leading global sales exceeding USD 1.2 billion annually (IQVIA, 2022). The drug’s affordability, established efficacy, and broad indications have sustained its market presence.

Current Market Dynamics

  • Market Penetration: OTC formulations are widely available across North America, Europe, and certain Asian markets. The drug's familiarity and low cost sustain high consumer demand, particularly among older adults and parents of young children.

  • Competitive Landscape: Newer antihistamines such as loratadine, cetirizine, and fexofenadine, featuring fewer sedative effects, have eroded part of diphenhydramine’s market share. Nonetheless, diphenhydramine remains preferred for its sedative properties and sleep aid applications.

  • Regulatory Trends: Regulatory agencies increasingly scrutinize anticholinergic burden, limiting use in elderly populations and prompting manufacturers to develop formulations with reduced side effects.

  • Emerging Challenges: The rising awareness of anticholinergic side effects, including cognitive impairment and increased risk of dementia, has prompted some markets to restrict OTC access or require labeling updates.

Opportunities in Niche Markets

  • Sleep Medicine: Diphenhydramine continues to be a top consumer choice for OTC sleep aids, especially among consumers seeking immediate relief at lower cost than prescription alternatives.

  • Functional Health Products: Market expansion into natural and herbal supplements incorporating diphenhydramine derivatives or analogs offers growth potential, provided safety profiles remain favorable.

Market Risks

  • Safety Concerns: Growing evidence linking anticholinergic medications to cognitive decline will challenge its OTC status in certain markets.

  • Competitive Innovation: Rapid development of newer antihistamines and sleep aids touting improved safety and tolerability reduces diphenhydramine’s appeal.

Market Projection

Future Growth Drivers

  • Aging Population: The increasing geriatric demographic sustains demand for sleep aids and allergy medications, many of which include diphenhydramine formulations.

  • Consumer Preference for Cost-Effective OTC Drugs: Continued reliance on OTC medications in developed and emerging markets influences steady demand.

  • Expanding Application Scope: Research exploring novel indications — such as neuroprotective strategies and adjunct treatments for pruritus — could open new markets if validated clinically.

Forecast (2023–2030)

Based on current data, the global diphenhydramine hydrochloride market is expected to grow at a compound annual growth rate (CAGR) of approximately 2.3% over the next decade, reaching around USD 1.4 billion by 2030. Growth will predominantly stem from emerging markets, aging populations, and ongoing consumer acceptance of OTC sleep aids.

Key factors influencing growth include:

  • Regulatory restrictions in developed markets due to safety concerns.

  • Increased emphasis on safe, side-effect-free medications.

  • Potential reformulations with minimized sedative or anticholinergic effects to accommodate aging populations.

Strategic Recommendations

Manufacturers should focus on:

  • Developing safer formulations with reduced anticholinergic activity.

  • Investing in clinical trials to expand therapeutic indications.

  • Engaging in transparent consumer education to highlight safety profiles.

  • Navigating regulatory landscapes carefully to maintain market access.

Key Takeaways

  • Clinical Trials: While traditionally stable, recent trials are exploring innovative uses for diphenhydramine hydrochloride, emphasizing its potential beyond classic allergy and sleep applications. Safety monitoring remains paramount, especially among vulnerable populations.

  • Market Dynamics: The drug remains a leading OTC sleep aid, but dominance is challenged by newer antihistamines with better safety profiles. Regulations and safety concerns may constrain future growth but also open avenues for reformulation.

  • Market Projection: Steady growth is anticipated, driven by demographic trends and consumer preferences. Market players should prioritize safety improvements and explore emerging therapeutic areas.

  • Risks and Opportunities: Safety concerns tied to anticholinergic effects pose risks but also create opportunities for innovation. Companies that proactively adapt formulations and marketing strategies will better position themselves.

  • Regulatory Landscape: Ongoing review of safety data necessitates vigilant regulatory compliance to sustain market access and brand reputation.

FAQs

  1. What are the primary medical uses of diphenhydramine hydrochloride today?
    It is mainly used to treat allergies, hay fever, and cold symptoms, and as an over-the-counter sleep aid due to its sedative properties.

  2. Are there ongoing clinical trials for new therapeutic applications of diphenhydramine?
    Yes. Recent research explores its potential neuroprotective effects, management of sleep disorders, and some dermatological uses, though these remain investigational.

  3. What safety concerns are associated with long-term or frequent use of diphenhydramine?
    Long-term use, especially in older adults, has been linked to anticholinergic side effects, including cognitive impairment, dizziness, urinary retention, and increased dementia risk.

  4. How is the market for diphenhydramine hydrochloride expected to evolve?
    The market is projected to experience moderate growth, with expansion driven by aging populations and ongoing demand for sleep aids, balanced against regulatory restrictions and safety concerns.

  5. What strategies can companies adopt to maintain competitiveness in the diphenhydramine market?
    Developing safer formulations, expanding indications through clinical research, ensuring regulatory compliance, and educating consumers on safe use are key strategies.

References

[1] IQVIA, 2022. Global OTC Drug Market Reports.
[2] U.S. Food and Drug Administration (FDA). Safety Alerts and Labeling Recommendations.
[3] World Health Organization (WHO). Medication Safety & Anticholinergic Burden Reports.
[4] ClinicalTrials.gov. Current Investigations on Diphenhydramine.

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