Prolonged cough lasting more than four weeks is common in children, but the best treatment is often unclear when no underlying disease can be found. This study aims to find out whether commonly used treatments help children with prolonged cough more effectively than placebo.

Children who take part will first undergo standard medical examinations, including lung function tests and a chest X-ray, to look for the cause of the cough. If no specific cause is found, the child may enter the study.

Children with a dry cough will be randomly assigned to receive either an inhaled corticosteroid (fluticasone) or a placebo inhaler for two months. Children with a wet or productive cough will be randomly assigned to receive either an oral antibiotic (amoxicillin-clavulanic acid) or a placebo medicine for 14 days. Neither the families nor the researchers will know which treatment the child receives during the study.

The main goal is to determine whether these treatments significantly reduce or stop the cough compared with placebo. The results will help improve treatment recommendations for children with prolonged cough and avoid unnecessary medication use.

Participation is voluntary, and parents provide written informed consent for their child.

Why is this study being done? A cough that lasts for more than four weeks is common in children and can be distressing for both the child and their family. In many cases, careful medical examinations do not reveal a clear underlying disease that would explain the symptoms. Despite this, children are often treated with medications such as inhaled corticosteroids or antibiotics, even though it is not always clear whether these treatments are truly beneficial.

The aim of this study is to find out whether two commonly used treatments are more effective than placebo in children with prolonged cough when no clear cause can be identified. By doing this, the study seeks to improve future care for children with prolonged cough and reduce unnecessary medication use.

Who is organising the study? The study is conducted by the Pirkanmaa Wellbeing Services County in Finland and led by an experienced paediatric specialist at Tampere University Hospital (TAYS). The research team specialises in children's respiratory diseases and follows national and international clinical research regulations.

Who can take part?

The study includes children who:

Have had a cough every day for more than four weeks Are otherwise generally healthy Do not have a previously diagnosed illness that could explain the cough

Before joining the study, all children undergo thorough and routine medical assessments to look for possible causes of the cough. These include a clinical examination, breathing tests, and a chest X-ray. Children whose cough can be explained by an underlying disease are not included in the study and will receive appropriate standard medical care outside the study.

Participation is completely voluntary. Parents or legal guardians must give written informed consent before a child can participate.

What treatments are studied?

Children are divided into two groups based on the type of cough they have:

1. Children with a dry cough

   These children receive either:

   An inhaled corticosteroid (fluticasone), which is commonly used to reduce airway inflammation, or A placebo inhaler, which looks and is used in the same way but contains no active medicine

   The treatment is taken twice daily for two months.

2. Children with a wet or productive cough

These children receive either:

An oral antibiotic (amoxicillin-clavulanic acid), often used to treat respiratory infections, or A placebo liquid, which looks and tastes similar but does not contain active medication

This treatment is taken for 14 days.

How is the study organised? This is a randomised, double-blind, placebo-controlled clinical trial, which is considered the most reliable way to study treatment effects.

This means:

Children are randomly assigned to receive either the active treatment or placebo Neither the families nor the researchers know which treatment a child receives during the study The treatments and placebos are designed to look and taste the same

These methods help ensure that the results are fair and unbiased.

What does the study measure?

The main outcome of the study is whether the child's cough:

Stops completely, or Decreases clearly (by at least 75%) compared with the start of the study

This improvement must last for several consecutive days to be counted as a meaningful result.

The study will compare how often this level of improvement occurs in children receiving active treatment versus placebo.

How many children will participate? The study aims to recruit about 100 children who are randomised into treatment or placebo groups. A larger group of children may be screened to ensure that only those who meet all study criteria are included.

Are there risks? All medications used in the study are already widely used in children and have well-known safety profiles. However, as with any medication, mild side effects are possible. Children with known serious allergies or previous severe reactions to the study drugs are not included.

The study includes careful monitoring, and families can contact the study team at any time if concerns arise. Participation can be stopped at any point without giving a reason, and stopping the study will not affect the child's future medical care.

Why is this study important?

This study will provide high-quality evidence on whether commonly used treatments actually help children with prolonged cough when no underlying disease is found. The results may:

Improve treatment recommendations Reduce unnecessary antibiotic and steroid use Support safer and more effective care for children

Ultimately, the findings aim to benefit children, families, and healthcare systems by promoting evidence-based treatment.

Inclusion Criteria:

• Prolonged cough lasting continuously for more than 4 weeks
• No chronic disease requiring continuous medication (i.e. a generally healthy child)
• No previous physician-diagnosed condition associated with prolonged cough episodes
• No physician-identified symptoms or findings suggestive of an underlying disease
• No prior physician-diagnosed allergic reaction or other severe or life-threatening adverse reaction to the investigational medicinal products (fluticasone or amoxicillin-clavulanic acid)
• No simultaneous participation in another clinical drug trial
• Parents/guardians have sufficient spoken and written Finnish language proficiency
• Written, voluntary informed consent provided by a parent or legal guardian

Exclusion Criteria:

Children with symptoms or findings suggestive of an underlying cause of cough, including:

• A previously physician-diagnosed disease associated with prolonged cough
• Clinical examination or history at the study visit raising suspicion of a disease associated with prolonged cough (positive "cough pointers")
• Abnormal lung function test
• Abnormal chest X-ray (peribronchial markings are permitted)

Additional exclusion criteria:

• Prior physician-diagnosed allergic reaction or other severe or life-threatening adverse reaction to the investigational medicinal products
• Simultaneous participation in another clinical drug trial
• Prolonged cough that has resolved spontaneously prior to the study visit