Alpha-Blockers in Allergic Rhinitis (MAN 01)

Inclusion criteria

• Male or female 18-70 years
• Able to provide informed consent
• Able to comply with the requirements of the protocol
• Diagnosis of allergic rhinitis
• Peak nasal inspiratory flow which is reversible to >20 l/min with oxymetazoline
• Positive skin prick test to at least one common aeroallergen
• Ability to withhold antihistamines, intranasal corticosteroids for duration of the study
• Agreement for their GP to be made aware of study participation and to receive feedback as relevant to the participant's well being

Exclusion criteria

• Pregnancy, planned pregnancy or lactation
• Respiratory tract infection in the previous 2 months
• Nasal polyps of more than Grade I on nasal endoscopy
• Any known adverse reaction to the Investigational Medicinal Product or other quinazolines
• Systolic BP <100mmHg
• Any degree of heart block
• Any clinically significant medical condition that may endanger the health or safety of the participant or jeopardise the protocol
• Participation within another clinical trial of investigational medicinal product within the last 30 days
• Under the age of 18
• Benign hyperplasia, chronic urinary tract infections, bladder stones, overflow bladder, anuria or progressive renal failure
• History of oesophageal or gastrointestinal obstruction or decreased lumen diameter of the gastrointestinal tract.
• Concomitant use of PDE5 inhibitors (sildenafil etc.)
• Alpha antagonists - this is the medication under investigation.
• Other cardiovascular medications including but not limited to:

ACE inhibitors, Angiotensin II antagonists, Beta blockers, calcium channel blockers, diuretics, nitrates, phosphodiesterase type-5 inhibitors or other vasodilating medications - these in combination with doxazosin carry an increased risk of symptomatic hypotension.

• Monoamine oxidase inhibitors (MAOIs) - antidepressant medication that can lead to significant hypotension in combination with alpha antagonists.
• Anxiolytics and hypnotics - enhanced hypotensive and sedative effects when alpha-blockers given in combination with these.
• Methyldopa and levodopa - potential enhanced hypotensive effect with alpha antagonists.
• Nasal corticosteroid spray - would confound study outcomes
• Oxymetazoline - this is used as an outcome of response in the study.
• Antihistamines - the participants will be undergoing a histamine nasal challenge.
• Sympathomimetics i.e. dopamine, ephedrine, epinephrine, metaraminol, methoxamine, phenylephrine- may reduce the effect of doxazosin.
• Any other medication, which in the opinion of the Investigator may put the participant at risk.