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Comparative Bioavailability of Inhaled Levodopa (Levodopa Cyclops) versus Inhaled Levodopa Powder with Carbidopa in Healthy Adults for Parkinson’s Disease

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What is this trial about?

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

The investigation focuses on Parkinson’s disease, a brain disorder that causes shaking, stiffness and slow movement. The medication being examined is levodopa, a drug that replaces dopamine, a chemical needed for smooth movement. To help levodopa work better and cause fewer side effects, a second medicine called carbidopa is given first. Two ways of delivering levodopa are compared: an inhaled powder called Inbrija (inhaled means breathed in as a powder) and a new inhaled powder that comes pre‑measured, named Levodopa Cyclops™.

The purpose of the study is to determine the dose at which the two inhaled forms provide a similar amount of levodopa in the body. Healthy adult volunteers will receive a single dose of each product on separate occasions, with a short break between each period. Before each inhaled dose, participants will take carbidopa by mouth about one hour earlier while fasting (no food). The study will record how quickly the medicine appears in the blood and will monitor safety through basic medical checks.

The research process

The trial runs in 10 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial study visit and fasting preparation

    Arrive at the study site on the scheduled day.

    Confirm that you have not eaten for at least eight hours before the visit (fasting).

    Receive written information about the study procedures.

  2. Step 2

    Carbidopa pre‑dose

    Take a single oral tablet containing 50 mg carbidopa exactly one hour before the levodopa dose.

    Carbidopa helps increase the amount of levodopa that reaches the brain.

  3. Step 3

    First levodopa administration (45 mg)

    Inhale a single dose of 45 mg levodopa using the levodopa cyclops inhaler.

    The dose is delivered as a powder that you breathe in through the mouth.

    Stay at the study site for a short monitoring period while blood samples are taken to measure drug levels.

  4. Step 4

    Washout period after first dose

    Wait for a minimum of 24 hours (or as instructed) before the next study period to allow the previous dose to clear from your body.

  5. Step 5

    Second levodopa administration (90 mg)

    Repeat the carbidopa pre‑dose of 50 mg one hour before the levodopa.

    Inhale a single dose of 90 mg levodopa using the same inhaler.

    Remain at the study site for monitoring and blood sampling as before.

  6. Step 6

    Washout period after second dose

    Wait for the required washout time before proceeding to the next period.

  7. Step 7

    Third levodopa administration (135 mg)

    Take the 50 mg carbidopa tablet one hour prior to levodopa.

    Inhale a single dose of 135 mg levodopa using the levodopa cyclops device.

    Stay for the monitoring period with blood draws to assess drug absorption.

  8. Step 8

    Washout period after third dose

    Observe the required interval to clear the previous dose before the final study period.

  9. Step 9

    Reference product administration (66 mg inbrija)

    Again take the 50 mg carbidopa tablet one hour before the levodopa dose.

    Inhale two hard capsules of inbrija, each containing 33 mg levodopa, for a total dose of 66 mg levodopa.

    Remain at the site for the same monitoring and blood sampling as in the previous periods.

  10. Step 10

    Final monitoring and study completion

    Undergo safety checks including physical examination, vital signs, and laboratory tests.

    Receive any final instructions from the study team.

    The study concludes after these assessments are completed.

Who can join the trial?

9 criteria

  • Male or female subject: You can be a man or a woman to join the study.
  • Age between 18 and 55 years: You must be at least 18 years old and not older than 55 when you sign the consent form.
  • Female subject who is NOT of reproductive potential: Women who cannot become pregnant may join. This includes women who have naturally stopped having periods (menopause) for at least 6 months with post‑menopausal hormone levels or for 12 months, women who had both ovaries removed (with or without the uterus) at least 6 weeks ago, or women who have had a permanent tubal ligation. “Amenorrhea” means no menstrual periods, and “follicle‑stimulating hormone (FSH)” is a blood test that confirms menopause.
  • Female subject who IS of reproductive potential: Women who could become pregnant must use a reliable birth‑control method and agree to keep using it until 30 days after the last dose of the study medicine.
  • Physically and mentally healthy as judged by a medical exam and standard laboratory examination: You must be in good overall health, both physically and mentally, based on a doctor’s check‑up and routine lab tests.
  • Non‑smokers or ex‑smokers (stopped at least 6 months ago) with a smoking history of ≤5 pack‑year equivalents (one pack per day for one year counts as one pack‑year). You must not use other nicotine products, and a urine test for cotinine (a nicotine by‑product) will confirm this.
  • BMI within the range of 18.0 to 30.0 kg/m²: Your body‑mass index, a measure of weight relative to height, must fall between these numbers.
  • Normal spirometry values at screening: Your lung function test must show that the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) are each between 80 % and 120 % of the expected value for your age, height, sex and ethnicity.
  • Informed consent given in written form: You must sign a written document that explains the study and confirms that you agree to take part.

Who cannot join the trial?

30 criteria

  • Being part of another clinical trial at the same time or within the past 90 days.
  • Having already been randomly assigned to this study more than once.
  • Being pregnant or nursing, or having a positive pregnancy test.
  • Weighing less than 40 kilograms (about 88 pounds).
  • Giving blood or losing more than 500 mL of blood (about a pint) within the past 90 days.
  • Having a history of drug abuse or illegal drug use – for example, marijuana within the last 6 months or drugs such as cocaine, amphetamines, or PCP within the last year.
  • Having an alcohol abuse problem – regularly drinking more than 2 units of alcohol per day (about 2 glasses of wine) or more than 10 units per week, or a past history of alcoholism.
  • Regularly drinking or eating foods with high caffeine (called methylxanthines) – more than the amount found in about 5 cups of coffee per day.
  • Testing positive on a drug screen.
  • Testing positive for alcohol at the screening visit.
  • Having significant allergies, such as to latex, asthma, or severe reactions to medicines or foods.
  • Having any drug allergy, especially to the study medicines levodopa or carbidopa, or being intolerant to common sugars like fructose, glucose, or lactose.
  • Having a current or past serious disease affecting the heart (cardiovascular), kidneys (renal), liver (hepatic), lungs (pulmonary), metabolism, hormones (endocrine), blood (hematological), digestive system (gastrointestinal), nerves (neurological), or mind (psychiatric).
  • Having a serious illness within 4 weeks before the screening visit.
  • Having major surgery on the stomach or intestines, except for removal of the appendix.
  • Having a chronic condition that could change how the body absorbs, moves, breaks down, or gets rid of the study drug.
  • Having a history of difficulty swallowing.
  • Testing positive for infections such as HIV, hepatitis B surface antigen (HBsAg), or hepatitis C antibodies (HCV).
  • Receiving long‑acting injectable medicines (those that stay in the body for more than a week) within the past 6 months.
  • Taking medicines that affect enzymes, damage organs (organotoxic), or last a long time, within the past 4 weeks.
  • Using any systemic (whole‑body) or topical (skin) medication, including over‑the‑counter drugs, antacids (like aluminum hydroxide or magnesium hydroxide), or herbal products (such as St. John’s wort or kava) within the past 2 weeks.
  • Using drugs known to change major organ function, such as barbiturates, phenothiazines, cimetidine, or omeprazole, within the past 60 days.
  • Having a resting blood pressure that is not between 100–135 mmHg (systolic) or 60–90 mmHg (diastolic).
  • Having a pulse rate that is not between 50–90 beats per minute.
  • Having a breathing rate that is not between 12–16 breaths per minute.
  • Having an under‑arm (axillary) temperature that is not between 35.5 °C and 37.1 °C (96.0–98.8 °F).
  • Having a significant abnormal finding on a resting 12‑lead ECG (electrocardiogram) test.
  • Having laboratory test results that are outside the normal range and could affect health.
  • Following a special diet for any reason, such as being vegetarian.
  • Being known or suspected to be unable to follow study rules, unreliable, unable to understand the study information, in severe financial difficulty, or under legal custody.
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Investigated drugs

  • Inbrija

    is an inhaled powder that contains levodopa. It is breathed in through the mouth, allowing the medicine to be absorbed quickly from the lungs into the bloodstream. In the study, it is used as the standard product to compare the new treatment against.

  • Carbidopa

    is a tablet taken by mouth before the levodopa medicines. It works by stopping the body from breaking down levodopa too early, so more of the levodopa can reach the brain where it is needed.

  • Levodopa Cyclops™

    is a new inhaled powder formulation of levodopa. Like Inbrija, it is breathed in so the drug can be absorbed through the lungs. The trial tests whether this new product provides a similar amount of levodopa in the blood as Inbrija.

What is already known about the treatment

  • Inbrija

    Inbrija is an inhalation powder contained in hard capsules that is taken using a small inhaler device, delivering levodopa directly to the lungs. It is an approved medicine used for the intermittent treatment of “OFF” episodes in adults with Parkinson’s disease who are already on levodopa therapy. The powder is quickly absorbed into the blood, where levodopa is turned into dopamine, the brain chemical that is low in Parkinson’s disease. It belongs to the class of dopamine precursors (levodopa).

  • Carbidopa

    Carbidopa is taken as an oral tablet, usually 50 mg about one hour before a levodopa dose. It is an approved component of Parkinson’s disease treatment that helps levodopa work better by stopping its conversion to dopamine outside the brain. By inhibiting the enzyme dopa‑decarboxylase in the body, more levodopa reaches the brain where it can be converted to dopamine. It is classified as a dopa‑decarboxylase inhibitor.

  • Levodopa Cyclops

    Levodopa Cyclops is a pre‑dispensed inhalation powder that is inhaled through a device, delivering a single oral inhaled dose of levodopa (e.g., 135 mg). It is an investigational product being studied for its bioavailability compared with Inbrija and is intended for intermittent treatment of “OFF” episodes in Parkinson’s disease. The inhaled levodopa is rapidly absorbed from the lungs and then converted to dopamine in the brain to improve movement control. It is also classified as a dopamine precursor (levodopa).

Investigated diseases

Parkinson's disease - It is a progressive disorder of the nervous system that mainly affects movement. Early signs often include a tremor at rest, muscle stiffness, and slower, smaller movements. As the condition advances, balance problems, difficulty walking, and changes in posture become more common. Non‑motor features such as sleep disturbances, constipation, and mood changes may also develop. The disease slowly worsens over time as dopamine‑producing brain cells are lost.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase ITrial ID2023-504687-42-00Protocol codeCPI23001Estimated enrolment26 patientsSponsorCCDRD Cooperative Clinical Drug Research and Development AG

sourced from the EU Clinical Trials Register and site verification

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This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).