The purpose of the study was to test if the PROPONENT® nasal spray works, if it is safe, and if it helps participants to stop using addictive nasal decongestant sprays. To be able to take part in the study, participants had to be at least 18 years old, suffer from a condition called "rebound nasal congestion" or "rhinitis medicamentosa (RM)", and be dependent on nasal decongestants. Participants were randomly assigned to receive either PROPONENT® nasal spray or a nasal spray with physiological saline during the 4-week study treatment period. Neither the participants nor their doctor knew which they were receiving. In total, 194 participants took part in this study in several hospitals in Norway.

The study included three visits to the study center: one at the beginning and one at the end of the treatment period, and a follow-up visit approximately 4 weeks after the end of study treatment. During the study treatment period, participants used 1-2 puffs of study nasal spray in each nostril in the morning and evening. They could use the nasal spray additional times if they felt the need due to nasal congestion, up to a maximum of 16 puffs a day. During they study treatment period, participants were asked to measure every morning and evening how much air they could maximally inhale through their nose using a simple instrument called Peak Nasal Inspiratory Flow (PNIF) meter. At the end of each week of the treatment period, participants were asked to report how bad their nasal problems had been during the past week using electronic questionnaires. At the follow-up visit, participants were asked if they could still manage without the decongestant nasal sprays they had been using before entering the study, and if they felt that they had become addicted to the study nasal spray.

This was a prospective, randomised, double-blind, multicenter, parallel-group study to evaluate Proponent Solution - Nasal Spray (PSNS) compared to sodium chloride 0.9% (Isotonic Saline Nasal Spray [ISNS]) for treatment of nasal congestion symptoms during RM while weaning from direct-acting alpha-adrenergic agonists, such as xylometazoline or oxymetazoline. The study aimed to recruit approximately 200 subjects (actual: 194 subjects) who should receive 4 weeks of treatment with PSNS or ISNS to evaluate the efficacy, safety, and tolerability.

Before study start, prospective subjects received a telephone call by the study personnel where they were informed about the study and asked to make notes of their daily use of xylometazoline or oxymetazoline each evening (including the number of doses used) for 7 days prior to start of study treatment. This data was transferred to an electronic diary (eDiary) for all subjects that were included in the study. Prospective subjects attended an enrolment visit (Visit 1) at the investigational site, where informed consent was discussed and signed. Eligible subjects were randomised (1:1) to receive the investigational device product (PSNS) or the comparator (ISNS), and self-administered the first dose of study treatment under supervision of the study personnel.

During the 4-week treatment period (28 days, -1 to +5 days), subjects self-administered the study nasal spray at a maximum dose of 16 puffs per day distributed over 1-2 puffs applied into each nostril 2-4 times daily. Subjects were asked to report daily their objective morning and evening PNIF meter results in an eDiary on a smartphone or laptop both before and 10 minutes after administration of 1-2 puffs of either PSNS or the comparator. Each week, subjects had to fill out electronic questionnaires assessing their nasal congestion/obstruction using validated scoring systems (NOSE and NOVAS-score). At 21-35 days after the end of study treatment (Visit 3), each subject was asked to complete a follow-up registration in the eDiary. During this assessment, it was also assessed whether the subject had become addicted to/physically dependent on the study nasal spray.

Inclusion Criteria:

1. Provide signed informed consent prior to any study-specific procedures.
2. Be 18 years of age or older.
3. Use xylometazoline or oxymetazoline nasal spray at least once daily over a period of 7 days, registered before entering the clinical study.
4. Be diagnosed with RM by a medical doctor. The subject needed/wanted to wean from direct-acting alpha-adrenergic agonists, such as xylometazoline or oxymetazoline.

Exclusion Criteria:

1. Had influenza, acute or chronic rhinitis (other than RM), acute sinusitis, suppurative tonsillitis, pneumonia, or tuberculosis.
2. Had taken any medication or cold remedies to treat common colds (including Proponent Solution - Nasal Spray [PSNS]) within the last week.
3. Had used glucocorticoids (tablets, injections, and topical inhalers) within the last week or will need this medication during the study.
4. Had serious primary cardiovascular, kidney, liver, neurological, psychiatric, or haematological disease.
5. Had a diagnosis of asthma, chronic obstructive pulmonary disease, chronic cough, or other significant acute or chronic respiratory conditions or disorders.
6. Had an allergic disease and require daily peroral antihistamines for the treatment of the disease during the inclusion period and the study.
7. Study subject was a current smoker.
8. Nasal disorder or nasal condition as a relevant septal deviation, polyposis, chronic rhinitis, ulcer, etc., and/or reconstructive surgery, that could impair nasal breathing.
9. Had a known ongoing cancer disease.
10. Was identified by the Investigator as inappropriate to participate in this study (e.g., inability to report daily using smartphone/computer [eDiary]).
11. Participated in other clinical trials within the last 3 months.
12. Had known allergy or hypersensitivity to the components of the investigational product.
13. Were pregnant or nursing.

Subjects were randomly assigned to treatment with PSNS or ISNS using a block size of 4. Randomisation codes were assigned strictly sequentially as subjects were eligible for randomisation. The randomisation list was generated by an independent statistician and was kept strictly confidential. The investigational medicinal device and the comparator nasal spray were distributed in identical packages.