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Effect of antimicrobial drugs on tacrolimus and mycophenolate mofetil pharmacokinetics in kidney transplant recipients

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on people who have received a Kidney transplantation. After the transplant, patients normally take two medicines, mycophenolate mofetil and tacrolimus, to keep the new organ from being rejected. The investigation looks at how taking ordinary antimicrobial drugs – medicines used to treat infections – might change the way these transplant medicines work in the body. “Pharmacokinetics” means how quickly a drug is absorbed, moves through the body, and is cleared out.

The purpose of the study is to find out whether antimicrobial medicines affect the levels of the transplant drugs in the blood and alter the composition of the gut microbiome. Participants will continue their regular transplant medication schedule, and when an antimicrobial drug is prescribed as part of normal care, additional blood samples will be collected at several time points to measure drug concentrations. Small stool samples may also be taken to examine changes in intestinal bacteria. The overall study period lasts several weeks, with follow‑up visits to monitor any differences.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Start study medication

    After joining the study you will begin taking the two study drugs as prescribed.

  2. Step 2

    Take mycophenolate mofetil

    Take a total of 2000 mg of mycophenolate mofetil each day by mouth.

    The dose is usually divided into four 500 mg film‑coated tablets taken with food, but follow the exact schedule given by the study team.

  3. Step 3

    Take tacrolimus

    Take a total of 30 mg of tacrolimus each day by mouth.

    The medication is supplied as 1 mg hard capsules; the number of capsules to reach the prescribed dose will be indicated by the study team, and the dose is typically taken once daily.

  4. Step 4

    Provide blood samples for pharmacokinetic analysis

    Attend scheduled clinic visits where a blood sample will be drawn to measure the levels of the study drugs in your bloodstream.

    Samples are collected at several time points after a dose to determine exposure (a u c) and peak concentration (c max).

    These measurements help assess how the drugs are processed in your body.

  5. Step 5

    Provide stool samples for microbiome assessment

    At designated visits you will be asked to give a stool sample.

    The sample is used to evaluate the composition of gut bacteria and how they may affect the study drugs.

  6. Step 6

    Continue medication and sample collection for the study period

    You will keep taking the prescribed doses of mycophenolate mofetil and tacrolimus for the entire duration of the trial.

    Regular blood and stool collections will continue according to the study schedule.

  7. Step 7

    Final assessment and end of study medication

    At the conclusion of the trial you will undergo a final assessment, which includes a last set of blood and stool samples.

    After this visit the study medication will be stopped as directed.

Who can join the trial?

5 criteria

  • Be a kidney transplant recipient who has been on a steady immunosuppressive therapy (medicines that keep the body from rejecting the new kidney) for at least two weeks and needs an antimicrobial treatment (antibiotic or similar drug) that will last more than five days; examples include ciprofloxacin, meropenem, trimethoprim‑sulfamethoxazole, or other similar drugs.
  • Currently take an immunosuppressive drug regimen that includes either Prograf® (tacrolimus taken twice daily) or Advagraf® (tacrolimus taken once daily) and/or CellCept®/Mycophenolate mofetil Accord® (mycophenolate mofetil taken twice daily). Tacrolimus and mycophenolate mofetil are medicines that help prevent the body from attacking the transplanted kidney.
  • Be 18 years of age or older.
  • Be able to follow the medical treatment plan on your own, without needing constant help.
  • Sign a written informed consent form agreeing to take part in the study.

Who cannot join the trial?

6 criteria

  • Had a kidney transplant that was rejected within the past month and was treated with the steroid medication methylprednisolone (a strong anti‑inflammatory drug).
  • Had an infection that required antibiotics in the last 12 weeks (about three months).
  • Has been admitted to the intensive care unit (ICU) because of an infection.
  • Has changed any medicines that can affect the study drugs tacrolimus (Tac) or mycophenolate mofetil (MMF) between study visits, such as (but not limited to) diltiazem, verapamil, phenytoin, carbamazepine, fluconazole, ketoconazole, voriconazole, ritonavir, cholestyramine, or rifampicin. These are drugs that can interfere with how Tac or MMF work in the body.
  • Has severe diarrhea at the time of the study tests, or has had unusually loose or watery stools for the week before the tests.
  • Is a woman who is breastfeeding, currently pregnant, or could become pregnant and is not using a highly effective birth control method.
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Investigated drugs

  • CellCept

    is a tablet that contains mycophenolate mofetil, a medicine that helps stop the immune system from attacking a newly transplanted kidney. In this study, participants take the tablet by mouth to see how other drugs might change the way mycophenolate works in the body and how it affects the gut bacteria.

  • Mycophenolate mofetil Accord

    is another brand of the same medicine, mycophenolate mofetil, also taken as a tablet by mouth. It serves the same purpose as CellCept – to suppress the immune response after a kidney transplant – and is used in the trial to compare how different antimicrobial drugs may influence its behavior in the body and the gut microbiome.

  • Advagraf

    is a hard capsule that contains tacrolimus, a medication that also suppresses the immune system to protect a transplanted kidney from rejection. Participants swallow the capsule, and the study looks at how antimicrobial drugs might affect the amount of tacrolimus that reaches the bloodstream and its impact on gut bacteria.

  • PROGRAF

    is another brand of tacrolimus, provided as a capsule taken by mouth. Like Advagraf, it works to prevent the immune system from attacking the new kidney, and the trial uses it to examine whether other drugs change its absorption and its interaction with the gut microbiome.

What is already known about the treatment

  • CellCept 500 mg film-coated tablets

    This medication is taken by mouth as a film‑coated tablet and is approved for use in preventing organ rejection after kidney transplantation. It contains mycophenolate mofetil, which works by blocking an enzyme needed for making DNA in certain immune cells, thereby lowering their activity. The drug belongs to the antimetabolite class of immunosuppressants and is well established in medical practice and literature. It is commonly prescribed to help kidney transplant patients maintain a healthy graft.

  • Mycophenolate mofetil Accord 500 mg film-coated tablets

    This product is also an oral film‑coated tablet used to stop the body from rejecting a new kidney. It contains the same active ingredient, mycophenolate mofetil, which stops a key step in DNA production for immune cells, reducing their ability to attack the transplanted organ. It is classified as an antimetabolite immunosuppressant and has a long record of safety and effectiveness in clinical studies. Like other forms of mycophenolate, it is a standard part of post‑transplant therapy.

  • Advagraf 1 mg prolonged-release hard capsules

    Advagraf is swallowed as a hard capsule that releases tacrolimus slowly over time, and it is approved to prevent rejection in kidney transplant recipients. Tacrolimus binds to a protein inside immune cells, blocking a signal pathway that would otherwise activate the cells to attack the new kidney. The drug is a calcineurin inhibitor, a well‑known class of immunosuppressive medicines, and is widely used and studied in transplant medicine. Its prolonged‑release formulation helps keep drug levels steady, improving convenience and adherence.

  • PROGRAF 1 mg capsule

    PROGRAF is an oral capsule containing tacrolimus, used to keep the immune system from rejecting a transplanted kidney. It works by attaching to a cellular protein that stops the activation of immune cells, thereby lowering the chance of organ damage. This medication belongs to the calcineurin inhibitor group and is an established, approved treatment with extensive clinical evidence. It is prescribed as part of the standard regimen for kidney transplant patients.

Investigated diseases

Kidney transplantation - Kidney transplantation is the surgical placement of a healthy donor kidney into a person whose own kidneys no longer work adequately. After surgery, the transplanted organ begins to filter blood, producing urine and helping to regulate fluid and electrolytes. Over time, the new kidney can maintain normal kidney function, but the recipient’s immune system may gradually recognize it as foreign, leading to a slow decline in function if not controlled. The transplanted kidney can also be affected by injuries, infections, or chronic changes that reduce its filtering ability. Monitoring of kidney performance shows how the organ adapts and ages within the recipient’s body.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-527106-20-00Protocol codeAXISEstimated enrolment120 patientsSponsorOslo University Hospital HF

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