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Diphenhydramine

Diphenhydramine, a widely used antihistamine, has been the subject of several clinical trials to evaluate its effectiveness and safety in treating allergies and related conditions. These studies have focused on various aspects, including its use in different age groups, formulations, and comparisons with other medications. This article summarizes key findings from clinical trials involving diphenhydramine, providing valuable insights for patients and healthcare providers.

Table of Contents

What is Diphenhydramine?

Diphenhydramine is a widely used medication that belongs to a class of drugs called antihistamines. It is commonly known by its brand name Benadryl[1]. Diphenhydramine is available over-the-counter and is used to treat various conditions, primarily those related to allergies and sleep issues.

Uses of Diphenhydramine

Diphenhydramine is used to treat several conditions, including:

  • Allergies: It helps relieve symptoms of hay fever and other upper respiratory allergies, such as sneezing, runny nose, and itchy eyes[2].
  • Insomnia: Due to its sedative effects, diphenhydramine is often used as a sleep aid to help people fall asleep faster[1].
  • Motion sickness: It can help prevent and treat nausea, vomiting, and dizziness associated with motion sickness.
  • Common cold symptoms: Diphenhydramine can help alleviate some symptoms of the common cold, such as sneezing and runny nose.

How Diphenhydramine Works

Diphenhydramine works by blocking the effects of histamine, a substance produced by the body during an allergic reaction. By blocking histamine, diphenhydramine helps reduce allergy symptoms. It also has a sedative effect on the brain, which is why it can cause drowsiness and help with sleep[1].

Formulations and Dosage

Diphenhydramine comes in various formulations, including:

  • Tablets
  • Capsules
  • Liquid form

The dosage of diphenhydramine can vary depending on the condition being treated and the patient’s age. For example, in one study, children aged 2 to 12 years were given a single liquid dose of diphenhydramine HCl (12.5 mg / 5 mL) followed by water, according to an age-weight dosing schedule[2]. Always follow the instructions provided by your healthcare provider or the product label.

Side Effects and Safety

While diphenhydramine is generally considered safe when used as directed, it can cause some side effects, including:

  • Drowsiness: This is the most common side effect and can affect your ability to drive or operate machinery[1].
  • Dry mouth
  • Dizziness
  • Constipation
  • Blurred vision

It’s important to note that diphenhydramine can interact with other medications and alcohol, potentially increasing its sedative effects. Always consult with your healthcare provider before taking diphenhydramine, especially if you’re taking other medications or have underlying health conditions.

Research and Clinical Trials

Several clinical trials have been conducted to study the effects and safety of diphenhydramine:

  • A study examined the next-day residual effects of a nighttime dose of diphenhydramine citrate 76 mg on simulated driving performance in normal volunteer subjects[1]. This research helps understand the potential impact of the medication on daily activities.
  • Another study focused on characterizing the pharmacokinetics (how the body processes the drug) of diphenhydramine in children and adolescents[2]. This type of research is crucial for determining appropriate dosages for different age groups.
  • A bioequivalence study compared two formulations of diphenhydramine hydrochloride: ULTRATAB Tablet versus KAPSEALS Capsule[3]. Such studies ensure that different formulations of the same medication have similar effects in the body.

These studies contribute to our understanding of how diphenhydramine works in different populations and help ensure its safe and effective use.

Aspect Details
Study Populations Children (2-12 years), Adolescents (12-18 years), Adults
Formulations Tested Liquid, Tablets (ULTRATAB), Capsules (KAPSEALS)
Key Measurements Pharmacokinetics, Bioequivalence, Safety, Efficacy
Conditions Studied Allergic Rhinitis, Nasal Congestion, Insomnia
Comparison Studies Bioequivalence between formulations, Comparisons with other antihistamines
Safety Assessments Adverse Events, Serious Adverse Events, Vital Signs Monitoring
Efficacy Measures Symptom relief, Sleep quality improvement, Pharmacokinetic parameters

FAQ

  • What is the purpose of studying diphenhydramine in children and adolescents? The purpose is to understand how diphenhydramine works in younger populations. A study (NCT00762749) aimed to characterize the pharmacokinetics of diphenhydramine in children aged 2 to 12 years and adolescents aged 12 to 18 years with hay fever or other upper respiratory allergies.
  • How is the bioequivalence of different diphenhydramine formulations tested? Bioequivalence is tested by comparing different formulations of diphenhydramine. For example, a study (NCT00662337) compared the bioequivalence of diphenhydramine hydrochloride in ULTRATAB tablet form versus KAPSEALS capsule form, measuring factors like maximum concentration (Cmax) and area under the curve (AUC).
  • What safety measures are typically included in diphenhydramine clinical trials? Safety assessments in diphenhydramine trials often include monitoring vital signs, tracking adverse events (AEs), and serious adverse events (SAEs). The frequency, severity, and relationship of these events to the drug are typically recorded throughout the study duration and for a follow-up period.
  • Are there studies comparing diphenhydramine to other allergy medications? Yes, some studies compare diphenhydramine to other allergy medications. For instance, a study (NCT05586763) compared the efficacy of metoclopramide, promethazine, and prochlorperazine in treating vertigo, which can be related to certain types of allergies or inner ear issues.
  • How do researchers measure the effectiveness of diphenhydramine in clinical trials? Researchers measure diphenhydramine's effectiveness through various methods, including pharmacokinetic parameters (how the drug moves through the body), symptom relief scales, and specific outcomes like sleep efficiency in insomnia-related studies. They may also use questionnaires and polysomnographic parameters to assess improvements in sleep quality when diphenhydramine is used for this purpose.

Ongoing Clinical Trials on Diphenhydramine

  • Study on the Effectiveness of Ublituximab and Drug Combination for Patients with Relapsing Multiple Sclerosis

    Recruiting

    1 1 1
    Investigated diseases:
    Investigated drugs:
    Poland

  • Study on Monitoring Untreated Multiple Myeloma in Patients Using Daratumumab, Bortezomib, Lenalidomide, and Dexamethasone or a New Drug Combination

    Recruiting

    1 1 1
    Investigated drugs:
    Austria Germany Greece Italy The Netherlands

  • Study of Tebentafusp and Pembrolizumab for Patients with Previously Treated Advanced Melanoma

    Recruiting

    1 1 1 1
    Investigated diseases:
    Investigated drugs:
    Austria Belgium France Germany Italy Poland +1

  • Study Comparing Axicabtagene Ciloleucel and Standard Treatment for Adults with High-Risk Large B-Cell Lymphoma

    Recruiting

    1 1 1 1
    Investigated diseases:
    Investigated drugs:
    Austria France Germany Italy The Netherlands Portugal +1

  • Study for Adults with Very High-Risk T-Cell Acute Lymphoblastic Leukemia Using Daratumumab and a Drug Combination

    Not recruiting

    1 1 1
    Investigated drugs:
    Italy

  • Study on the Safety and Effects of AZD7789 for Patients with Relapsed or Refractory Classical Hodgkin Lymphoma

    Not recruiting

    1 1 1
    Investigated drugs:
    Denmark France Italy Spain

  • Study on Ublituximab and Drug Combination for Patients with Myasthenia Gravis or Relapsing Multiple Sclerosis

    Not recruiting

    1 1 1
    Investigated diseases:
    Investigated drugs:
    Poland

  • Study Comparing ABBV-383 with Standard Therapies for Adults with Relapsed or Refractory Multiple Myeloma

    Not recruiting

    1 1 1 1
    Investigated drugs:
    Austria Belgium Czechia Denmark France Germany +7

  • Study on the Safety and Effects of Forimtamig, Tocilizumab, and Daratumumab in Patients with Relapsed or Refractory Multiple Myeloma

    Not recruiting

    1 1 1
    Investigated drugs:
    Denmark France Germany Italy Spain

  • Study on BI-1910 and Pembrolizumab for Patients with Advanced Solid Tumors

    Not recruiting

    1 1 1
    Investigated drugs:
    Denmark Germany Poland Spain Sweden

Glossary

  • Pharmacokinetics: The study of how a drug moves through the body, including its absorption, distribution, metabolism, and excretion.
  • Bioequivalence: The property of two drug products having the same active ingredient, dosage form, strength, and route of administration to be pharmaceutically equivalent and to have similar biological effects.
  • Cmax: The maximum concentration of a drug in the blood after it has been administered.
  • AUC (Area Under the Curve): A measure of the total exposure to a drug over time, used to assess bioequivalence and drug effectiveness.
  • Adverse Event (AE): Any unfavorable and unintended sign, symptom, or disease temporarily associated with the use of a medical treatment or procedure.
  • Serious Adverse Event (SAE): An adverse event that results in death, is life-threatening, requires hospitalization, causes a significant incapacity, or results in a congenital anomaly/birth defect.
  • Polysomnographic parameters: Measurements taken during a sleep study, including brain waves, eye movements, muscle activity, and breathing patterns.
  • Allergic Rhinitis: Inflammation of the nasal passages caused by an allergic reaction, commonly known as hay fever.
  • Placebo: An inactive substance or treatment used in clinical trials as a control to compare against the effects of the drug being tested.
  • Crossover study: A type of clinical trial where participants receive different treatments in a specific order, allowing each participant to serve as their own control.

References

  1. https://clinicaltrials.gov/study/NCT01888497
  2. https://clinicaltrials.gov/study/NCT00762749
  3. https://clinicaltrials.gov/study/NCT00662337