Bioavailability of paracetamol and naproxen from a fixed‑dose tablet compared with separate paracetamol and naproxen tablets in healthy adults

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What is this study about?

The study enrolls healthy adult volunteers to compare the absorption of a combination tablet that contains paracetamol and naproxen with the absorption of the separate tablets Panadol Advance (which contains paracetamol) and Naprosyn (which contains naproxen). The combination tablet is identified as Haleon Immediate Release Tablet. The purpose of the study is to assess the bioavailability of the two pain‑relieving ingredients.

Each participant will receive all four treatments in a random order, with a short break between each dose. Some doses are taken on an empty stomach (fasted) and some after a light meal (fed) to see how food affects absorption. Small blood samples are collected after each dose to measure how much of the medicines enter the bloodstream.

Throughout the study, participants’ vital signs, such as blood pressure and heart rate, are checked and laboratory tests are performed to monitor safety. Any side effects that occur are recorded and evaluated.

1 initial visit and baseline assessments

you arrive at the clinic after agreeing to take part in the study. a brief health check is performed to confirm that you are a healthy adult and not taking any other medicines.

baseline measurements such as blood pressure, heart rate, and basic blood tests are taken to have a reference point for later comparisons.

2 first treatment period

you receive the first of four assigned treatments. the order of the treatments is decided by the study design, not by you.

if the assigned treatment is the test (paracetamol 500 mg + naproxen 125 mg) in a fasted condition, you must not eat for at least ten hours before the visit. you take two tablets, each containing 500 mg of paracetamol and 125 mg of naproxen, with a small amount of water.

if the assigned treatment is the reference 1 (naprosyn 250 mg) in a fasted condition, you also fast for at least ten hours and then take one tablet containing 250 mg of naproxen with water.

if the assigned treatment is the reference 2 (panadol advance 500 mg) in a fasted condition, you fast for at least ten hours and take two tablets, each containing 500 mg of paracetamol, with water.

after taking the medicine, you remain at the clinic for several hours while blood samples are drawn at predefined times to measure how much of the drug enters your bloodstream.

3 washout period

following the blood sampling, you return home and wait for a short break (typically a few days) before the next treatment. this break allows the previous medicine to leave your body completely.

4 second treatment period

you come back to the clinic for the second assigned treatment and repeat the same procedures as in step 2, using the specific tablets and fasting or feeding instructions that correspond to this treatment.

5 washout period

another short break is observed before the third treatment, ensuring no overlap of medicines.

6 third treatment period

you attend the clinic for the third assigned treatment and follow the same dosing and sampling steps as previously described.

7 washout period

a final short break is taken before the last treatment.

8 fourth treatment period (fed condition for test)

for the test under a fed condition, you eat a standard meal provided by the clinic. after the meal, you take two tablets, each containing 500 mg of paracetamol and 125 mg of naproxen, with water.

blood samples are collected at the same intervals as in the fasted visits to compare how food affects drug absorption.

9 final safety check

after the last blood draw, a final health assessment is performed to ensure you have returned to your normal condition.

any side effects that occurred during the study are recorded, and you receive a summary of the study procedures you completed.

Who Can Join the Study?

Have a personally signed and dated informed consent document showing you understand the study, including the genotyping (a simple DNA test) that will be done.
Be a male or female between 18 and 55 years old.
Be willing and able to keep all scheduled visits, take the study medication, and complete laboratory tests and other study procedures.
Be a healthy participant, meaning you are in generally good physical health with no important problems found in your medical history, a full physical exam, blood pressure and pulse check, a 12‑lead ECG (a heart rhythm test), or lab tests.
Have a Body Mass Index (BMI) from 18.5 to 30.0 and weigh at least 50 kg (about 110 lb).
If you are a woman of childbearing potential, you must agree to use a highly effective method of contraception (birth control) during the study and for at least 7 days after the last dose.

Who Cannot Join the Study?

Having heart problems or blood‑related diseases that could affect safety or how the medicine works.
Having liver, pancreas, or kidney diseases that could affect safety, tolerance, or how the medicine is processed.
Having stomach or intestinal disorders that could affect safety, tolerance, absorption, or how the medicine is processed.
Having had major stomach or intestinal surgery such as removal of part of the stomach, gastric bypass, or bowel removal (minor surgery like appendix removal is allowed).
Having inflammatory bowel disease or a history of stomach ulcers or bleeding.
Having metabolic, hormonal, or immune system diseases (for example diabetes, metabolic syndrome, or autoimmune disorders) that could affect safety or how the medicine works.
Having serious brain or mental health conditions now or in the past.
Having a current or recent serious infection or fever within two weeks before the study starts.
Having a condition that reduces the body’s glutathione (a protective substance) due to eating disorders, cystic fibrosis, HIV infection, severe starvation, or extreme weight loss.
Having blockage of the urinary system (for example from an enlarged prostate) or trouble emptying the bladder during screening.
Having a history of severe or multiple drug allergies unless the doctor decides they are not relevant to the study.
Having an allergic reaction (such as breathing trouble, nasal symptoms, swelling of the face or skin rash) to the study drugs, aspirin, other pain‑relieving medicines (NSAIDs), or any ingredient in the tablets.
Having a resting blood pressure that is too low ( 139 mmHg systolic).
Having a resting blood pressure that is too low ( 89 mmHg diastolic).
Having a resting heart rate lower than 50 beats per minute or higher than 90 beats per minute.
Having a heart‑electrical test (QTc) longer than 450 ms for men or 470 ms for women.
Having lab results showing high blood urea nitrogen (≥ 35 mg/dL) or high urea (≥ 5.85 mmol/L), serum creatinine more than 0.1 mg/dL above the normal limit, an estimated kidney filtration rate (eGFR) of 90 mL/min/1.73 m² or higher, or the presence of protein or blood in the urine.
Having liver enzyme levels (GGT, ALP, or AST) that are 1.2 times above the normal limit, or bilirubin more than 20 % above the normal limit, unless you have Gilbert’s syndrome with otherwise normal liver tests, in which case bilirubin may be up to twice normal.
Having a hemoglobin level below 12.0 g/dL for men or below 11.5 g/dL for women (a measure of blood’s ability to carry oxygen).
Testing positive for HIV, hepatitis B surface antigen, hepatitis C antibodies, or hepatitis B core antibodies.
Having any lab values outside the normal range unless the doctor decides they are not important for the study.
Having any acute or chronic illness that could change how the medicine is processed in the body.
Having a history of alcohol dependence.
Testing positive for alcohol, nicotine (cotinine), or illegal drugs at the screening visit.
Drinking 24 g or more of pure alcohol per day for men or 12 g or more for women (about two standard drinks for men, one for women).
Having used illegal drugs within the past year, marijuana within the past month, or hard drugs (such as cocaine, PCP, crack, heroin, or amphetamines) within the past three months.
Having donated blood or lost more than 400 ml of blood in the two months before joining the study.
Being a current smoker or using nicotine products within the past three months, or having a positive urine test for nicotine.
Following a diet that could affect how the medicine is absorbed (for example, very high‑fat or very low‑calorie diets).
Having taken certain long‑term medications that increase liver enzyme activity, such as carbamazepine, phenobarbital, phenytoin, primidone, rifampicin, or St John’s Wort.
Having taken part in another clinical trial with an investigational drug within the last two months.
Being enrolled in another clinical trial at the same time.
Having frequent migraine attacks.
Having a positive pregnancy test at screening or on the day of hospital admission.
Being pregnant or breast‑feeding.
Being a female who does not agree to use highly effective birth control methods.
Being considered vulnerable because of legal detention, close relationship with the study staff, or being an employee or student of the research site or sponsor.
Being suspected or known to be unlikely to follow the study instructions.
Being unable to understand written or spoken instructions about the study’s risks and requirements.
Having a history of major gastrointestinal surgery (such as gastrectomy, gastroenterostomy, bowel resection, gastric bypass, gastric stapling, or gastric banding) – note that minor surgeries like appendectomy are allowed.
Having a history of inflammatory bowel disease or gastrointestinal bleeding, including peptic ulcers.
Having a history of metabolic, endocrine, or immune system diseases (such as diabetes, metabolic syndrome, or autoimmune disorders) that could affect safety or how the medicine works.
Having acute or chronic central nervous system or psychiatric disorders.
Having a recent or ongoing serious infection or fever within two weeks before the study starts.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Syefojju Rshuzjd Cqxqsbzu im Dujn Rnfgchwy axr Dmdrhdtwnwx Grsu	Erfurt	Germany

Trial status

Country	Status	Recruitment Start
Germany	Not yet recruiting	25.09.2026

Trial locations

Investigated Drugs:

Panadol Advance is a tablet that contains the pain‑relieving ingredient paracetamol. In this study it is used as a reference product to show how paracetamol alone is absorbed in the body when taken on an empty stomach.

Naprosyn is a tablet that contains the anti‑inflammatory drug naproxen. It is used as a reference product to show how naproxen alone is absorbed in the body under the same fasted conditions.

MFC-06285 is a single tablet that combines both paracetamol and naproxen. This combination tablet is the test product, and the trial looks at how the two medicines are absorbed together compared with taking each one separately.

Trial ID:

2025-524663-20-00

Protocol code:

300259

Trial Phase:

Human Pharmacology (Phase I) – Other

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Bioavailability of paracetamol and naproxen from a fixed‑dose tablet compared with separate paracetamol and naproxen tablets in healthy adults

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?