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 thestudy

• Agreement for their GP to be made aware of study participation and to receive feedbackas 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 otherquinazolines

• Systolic BP <100mmHg

• Any degree of heart block

• Any clinically significant medical condition that may endanger the health or safety ofthe participant or jeopardise the protocol

• Participation within another clinical trial of investigational medicinal productwithin the last 30 days

• Under the age of 18

• Benign hyperplasia, chronic urinary tract infections, bladder stones, overflowbladder, anuria or progressive renal failure

• History of oesophageal or gastrointestinal obstruction or decreased lumen diameter ofthe 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 tosignificant hypotension in combination with alpha antagonists.

• Anxiolytics and hypnotics - enhanced hypotensive and sedative effects whenalpha-blockers given in combination with these.

• Methyldopa and levodopa - potential enhanced hypotensive effect with alphaantagonists.

• 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 participantat risk.