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The Effect of Concomitant Administration of Erythromycin and Diltiazem on CYP3A Activity in Healthy Volunteers

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00318201
Recruitment Status : Completed
First Posted : April 26, 2006
Last Update Posted : April 6, 2012
Information provided by:
Indiana University

Brief Summary:

We, the researchers at the Indiana University School of Medicine, are doing this study to better understand how the effects of certain medications are altered when taken simultaneously, or in combination with each other. We will also look at how each volunteer's genes (DNA) may affect the way these medications are metabolized.


We will test the hypothesis that the extent of drug-drug interaction caused by the combination of erythromycin and diltiazem is not predictable from the extent of interaction produced by each inhibitor alone. Specifically we will test the hypothesis that the combination of erythromycin and diltiazem will cause a greater decrease in midazolam intravenous and oral clearance than the sum of the decreases caused by each inhibitor alone.

Condition or disease Intervention/treatment Phase
Healthy Drug: Erythromycin Drug: Diltiazem Phase 4

Detailed Description:
Many drugs such as diltiazem are metabolized by CYP3A4, the cytochrome P450 enzyme responsible for the metabolism of erythromycin and when given together, the possibility exists that one drug inhibits the metabolism of the other leading to an increase in plasma concentration. The magnitude of this interaction is not known. It is therefore important to define this effect because diltiazem is a drug that is used commonly to treat hypertension, angina and atrial fibrillation and these patients may be given erythromycin for the treatment of intercurrent bacterial infections.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 7 participants
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: The Effect of Concomitant Administration of Erythromycin and Diltiazem on CYP3A Activity in Healthy Volunteers
Study Start Date : April 2006
Actual Study Completion Date : December 2007

Arm Intervention/treatment
Experimental: 1
Altered efficacy for drug to drug interaction of diltiazam with erythromycin
Drug: Erythromycin
Drug: Diltiazem

Primary Outcome Measures :
  1. Primary Aims: To quantify the extent of the drug-drug interaction between erythromycin and midazolam [ Time Frame: 2 days ]
  2. To quantify the extent of the drug-drug interaction between diltiazem and midazolam [ Time Frame: 2 days ]
  3. To quantify the extent of the drug-drug interaction between the combination of diltiazem and erythromycin, and midazolam [ Time Frame: 2 days ]

Secondary Outcome Measures :
  1. Secondary Aims: To quantify the effects of erythromycin, diltiazem, and the combination of erythromycin and diltiazem on the electrocardiogram (EKG) PR interval [ Time Frame: 2 days ]
  2. To quantify the effects of erythromycin, diltiazem, and the combination of erythromycin and diltiazem on the heart-rate corrected QT interval of the EKG [ Time Frame: 2 days ]

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

Approximately 45 healthy volunteers may be recruited to participate in the study, with a goal of 15 healthy volunteers (7 or 8 males) completing the entire four phases. All potential subjects:

  1. Must be a non-smoker
  2. Between 18 to 50 years of age
  3. Have a body mass index of 30 or less
  4. Must be willing to undergo a screening physical examination and proven to be free from metabolic, cardiac, pulmonary, renal or hepatic dysfunction as determined by the screening physical, medical history, 12-lead electrocardiography, and laboratory values which include: a CMP (complete metabolic profile), a CBC/diff/plt (complete blood count with differential and platelet count), serum pregnancy test (if applicable), and UA (urinalysis). Also, given the uncertain effects of these drugs on the fetus and the fact that hormonal contraceptives are prohibited, the female subjects should be on two other forms of birth control (e.g. condom, contraceptive foam).

Exclusion Criteria:

Potential volunteers will be excluded:

  1. If they have allergies or are hypersensitive to any of the study medications:

    A. Midazolam (Versed) or related benzodiazepines drugs such as diazepam (Valium) or alprazolam (Xanax).

    B. Diltiazem (Cardizem, Dilacor) or related calcium channel blockers such as verapamil (Calan, Isoptin).

    C. Erythromycin (Erythrocin, E-mycin, Ery-tab) or related antibiotics such as clarithromycin (Biaxin) or have experienced abdominal pain when taking erythromycin or other related medications.

  2. If they are taking any prescription medication on a regular basis including contraceptives such as oral birth control pills, transdermal patches or injections (Depo-Provera).
  3. If they are taking over-the-counter medications, any herbal or dietary supplement (including Benadryl, Sudafed, St. John's wort, herbal teas, vitamins and garlic supplements) that cannot be stopped for the study duration. Use of over-the-counter drugs for the treatment of minor, short-lived (2 to 3 days) symptoms may be allowable (such as Tylenol) but must first be approved by a study investigator.
  4. If they have donated blood within the past two months, or are anemic (have a hemoglobin level less than 12.5 mg/dl).
  5. If they weigh less than 52 kg, or have a BMI (Body Mass Index) greater than 32.
  6. If they have a screening or baseline EKG reading that is abnormal or could place them at higher risk as decided by the study doctors (baseline corrected QT interval in the EKG of 450 msec or greater or a baseline PR interval in the EKG of 210 msec or greater).
  7. If they have a history of bradycardia or consistently have a heart rate less than 55 beats per minutes.
  8. If they have any history of heart disease or have a family medical history of sudden death (heart stopping suddenly without warning).
  9. If they have a history of psychiatric problems that may be exacerbated by participation in this study, or if the subject can not state a good understanding of this study's risks and requirements.
  10. If they have a positive serum pregnancy test during the screening process or have a positive urine pregnancy test (UPT) which will be obtained just prior to each of the four study phases.
  11. If they are currently breastfeeding.
  12. If they have participated in any other study in which they have taken a research medication within the past three months.
  13. If they have a history of alcohol or drug abuse, or have used tobacco or marijuana within the past three months.
  14. If they are unwilling or unable to refrain from using drugs, alcohol, or any food listed on the exclusion list below during this study.
  15. If they are an employee or student under the supervision of any study investigator.
  16. If they are unwilling or unable to follow the study rules.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00318201

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United States, Indiana
Indiana University Medical Center / GCRC
Indianapolis, Indiana, United States, 46202
Sponsors and Collaborators
Indiana University School of Medicine
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Principal Investigator: Stephen D Hall, PhD Indiana University

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Responsible Party: Stephen D. Hall, Indiana University Identifier: NCT00318201    
Other Study ID Numbers: # 0412-09
MO1RR000750/GCRC #1267
R01GM067308 ( U.S. NIH Grant/Contract )
First Posted: April 26, 2006    Key Record Dates
Last Update Posted: April 6, 2012
Last Verified: December 2007
Keywords provided by Indiana University:
Healthy Subjects
Additional relevant MeSH terms:
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Erythromycin Estolate
Erythromycin Ethylsuccinate
Erythromycin stearate
Antihypertensive Agents
Calcium Channel Blockers
Membrane Transport Modulators
Molecular Mechanisms of Pharmacological Action
Calcium-Regulating Hormones and Agents
Physiological Effects of Drugs
Vasodilator Agents
Anti-Bacterial Agents
Anti-Infective Agents
Gastrointestinal Agents
Protein Synthesis Inhibitors
Enzyme Inhibitors