Rhinitis medicamentosa (RM) is a form of non-allergic medication-induced rhinitis characterised by nasal congestion. This nasal congestion is the result of the overuse of intranasal decongestants which leads to rebound congestion when the medication wears off. This prompts the user of the nasal decongestant to administer more in order to obtain relief from the feeling of a blocked nose. Therefore, the patient ends up in a vicious cycle caused and temporarily relieved by the use of medication.The diagnosis of rhinitis medicamentosa depends greatly on the history of prolonged use of the nasal decongestant, since real diagnostic criteria have not yet been established. It is unclear if these patients suffer from an underlying (undetected and/or untreated) nasal condition which might have caused the patient to start using the nasal decongestant in the first place. Therefore, the aim of the first part of this study (Part A) is to characterize patients with long-term use of nasal decongestants to examine if an underlying nasal condition is present. The investigators will include healthy volunteers in part A of the study to be able to compare their test results with those of patients with long-term use of nasal decongestants and hence be able to detect differences.

Thus far, the treatment of RM has been the topic of debate. Several treatment regimens have been proposed in literature, but most study authors agree that it is essential to stop the overuse of the nasal decongestant either immediately or gradually to limit withdrawal symptoms. For this part of the study (Part B: intervention study), the investigators aim to reduce the long-term use of nasal decongestants based on a structured withdrawal programme comprising medication (nasal corticosteroid spray) and motivational interviewing. Only patients with long-term use of nasal decongestants are eligible to participate in this part of the study. They will be rescreened prior to inclusion into this part of the study.

The study comprises two parts:

• Part A: Characterisation study (both healthy volunteers and patients with long-term use of nasal decongestants)
• Part B: Intervention study (only patients with long-term use of nasal decongestants). Patients will be rescreened prior to inclusion into part B of the study. Participants will receive the intervention (Mometasone furoate nasal spray) during a 12-week period

Part A (characterisation study) consists of three study-related contact moments:

1. Screening visit
2. Telephone contact
3. Ear-, nose- and throat examination (actual characterisation study)

Part B (intervention study) consists of five contact moments:

1. Start-up of the intervention
2. Telephone contact (during follow-up 1 period)
3. Follow-up 1 (After 6 weeks of intervention*)
4. Follow-up 2 (After 12 weeks of intervention*)
5. Telephone follow-up (6 months post start-up of the intervention*) * Study windows foreseen in the protocol

Procedures performed during part A of the study:

• Peak Nasal Inspiratory Flow (PNIF) measurements
• Nasal endoscopy
• Collection of blood samples and nasal secretions
• Completion of questionnaires
• Completion of patient diary
• Collection of data regarding medication use
• Skin prick testing
• Completion of patient diary
• Medical photography of the face and nose
• Telephone follow-up

Procedures performed during part B of the study:

• Urine pregnancy test
• Collection of data regarding medication use
• Counselling conversations with the researchers
• Completion of questionnaires
• Completion of patient diary
• Drug accountability
• Daily administration of Mometasone furoate (by the patients themselves, during a 12 week period)
• PNIF measurements
• Nasal endoscopy
• Collection of blood samples and nasal secretions
• Telephone follow-up

Inclusion Criteria Healthy Volunteers (only included in part A of the study):

• Aged 18 years or older
• Sufficient knowledge of the Dutch language

Exclusion Criteria Healthy Volunteers (only included in part A of the study):

• Subjective presence of nasal disease (i.e. the study subject indicates to experience any nasal symptoms, an occasional common cold not taken into account)
• Established diagnosis of a nasal disorder (e.g. allergy, nasal polyps, …) or a positive allergy test (skin prick test or blood test)
• Prior nasal surgery
• Asthma
• Use of an oral corticosteroid in the month prior to the screening visit
• Significant disease(s) that might interfere with the study, based on the judgement of the investigator
• Current use of a nasal decongestant, more than two episodes of 7 days use of a nasal decongestant in the previous year or less than two episodes of 7 days use (in the previous year) but last use less than a month prior to the screening visit
• Other medication used to treat nasal symptoms (intranasal corticosteroids, oral or intranasal antihistamines, oral decongestants …)
• History of rhinitis medicamentosa (either patient-reported long-term use of a nasal decongestant or a diagnosis of rhinitis medicamentosa)
• Pregnancy, trying to become pregnant (during the duration of the study) or breastfeeding

Inclusion Criteria patients with long-term use of nasal decongestants: part A:

• Aged 18 years or older
• Daily use of a nasal decongestant for at least 6 months. Following ATC-codes are considered, when the spray or drops contain a nasal decongestant and the drug is thus intended for short-term use only: R01AA, R01AB, R01AD52, R01AD53
• Sufficient knowledge of the Dutch language

Exclusion Criteria patients with long-term use of nasal decongestants: part A:

• Pregnancy, trying to become pregnant (during the duration of the study) or breastfeeding
• Use of an oral corticosteroid in the month prior to the screening visit
• Use of an oral decongestant in the week prior to the screening visit
• Significant disease(s) that might interfere with the study, based on the judgement of the investigator

Inclusion Criteria patients with long-term use of nasal decongestants: part B:

• Aged 18 years or older
• Daily use of a nasal decongestant for at least 6 months.Following ATC-codes are considered, when the spray or drops contain a nasal decongestant and the drug is thus intended for short-term use only: R01AA, R01AB, R01AD52, R01AD53
• Sufficient knowledge of the Dutch language

Exclusion Criteria patients with long-term use of nasal decongestants: part B:

• Pregnancy, trying to become pregnant (during the duration of the study) or breastfeeding
• Glaucoma
• Use of an oral corticosteroid in the month prior to the start of the intervention
• Use of an oral decongestant in the week prior to the start of the intervention
• Significant disease(s) that might interfere with the study, based on the judgement of the investigator