The most commonly repoed ADRs are oral dryness, ocular hyperaemia and burning/stinging, all occurring in 22 to 25% of patients. They are usually transient and not commonly of a nature serious enough to require discontinuation of treatment. Symptoms of ocular allergic reactions have been repoed to have occurred in 12.7% of subjects in clinical trials (causing withdrawal in 11.5% of subjects), with onset being between 3 and 9 months in the majority of patients. The following convention has been used for classification of frequency of undesirable effects: Very common : >=1 in 10. Common : >=1 in 100 and <1 in 10. Uncommon : >=1 in 1,000 and <1 in 100. Rare : >=1 in 10,000 and <1 in 1,000. Very rare : < 1 in 10,000. Not known (cannot be estimated from the available data) Within each frequency grouping, undesired effects are presented in order of decreasing seriousness. Cardiac disorders: Uncommon: Palpitations/arrhythmias (including bradycardia and tachycardia). Nervous system disorders: Very common: Headache, drowsiness. Common: Dizziness, abnormal taste. Very rare: Syncope Eye disorders: Very common : Ocular irritation including allergic reactions (hyperaemia, burning, stinging, pruritis, foreign body sensation, conjunctival follicles); blurred vision, allergic blepharitis, allergic blepharoconjuctivitis, allergic conjunctivitis, ocular allergic reaction and follicular conjunctivitis. Common: Local irritation (eyelid hyperaemia and oedema, blepharitis, conjunctival oedema and discharge, ocular pain and tearing); photophobia; corneal erosion and staining; ocular dryness; conjunctival blanching; abnormal vision; conjunctivitis. Very rare : Iritis (anterior uveitis); miosis. Respiratory, thoracic and mediastinal disorders: Common: Upper respiratory symptoms. Uncommon: Nasal dryness. Rare: Dyspnoea Gastrointestinal disorders: Very common: Oral dryness. Common: Gastrointestinal symptoms. Vascular disorders: Very rare: Hypeension, hypotension. General disorders and administration site conditions: Very common: Fatigue. Common: Asthenia. Immune system disorders: Uncommon: Systemic allergic reactions. Psychiatric disorders: Uncommon: Depression. Very rare: Insomnia. The following adverse reactions have been identified during post-marketing use of Brimonidine eye drops in clinical practice. Because they are repoed voluntarily from a population of unknown size, estimates of frequency cannot be made. Not known: Eye disorders Iridocyclitis (anterior uveitis) Eyelid pruritus Skin and subcutaneous tissue disorders Skin reaction including erythema, face oedema, pruritus, rash and vasodilation