ALLEREX EYE DROPS

Indications

• Allergic rhinitis
• Urticaria
• Allergic conjunctivitis
• Other allergic symptoms

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations.

Adults: Refer to the BNF for specific dosing recommendations.

Mechanism of action

Antazoline binds to the histamine H1 receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine. Antihistamines, including antazoline, act as competitive, reversible inhibitors of the action of histamine at the H1 receptor, effectively preventing histamine from exerting its effects.

Pharmacodynamics

Antazoline is a histamine H1 receptor antagonist that selectively binds to but does not activate histamine H1 receptors. By blocking these receptors, it inhibits the physiological actions of endogenous histamine, leading to a reduction in symptoms associated with allergic reactions, such as vasodilation, increased vascular permeability, and sensory nerve stimulation.

Pharmacokinetics

Antazoline is absorbed after oral administration and is distributed throughout the body tissues. It undergoes hepatic metabolism and is excreted in the urine. The duration of action may vary, and specific pharmacokinetic parameters such as half-life and clearance rates can depend on individual patient factors.

Adverse effects

• Drowsiness
• Dry mouth
• Dizziness
• Blurred vision
• Gastrointestinal disturbances

Precautions

• Use caution in patients with glaucoma
• Avoid in patients with prostatic hypertrophy
• Caution is advised in patients with cardiovascular disease

Pregnancy

Antazoline should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Antazoline is excreted in breast milk, and caution should be exercised when administering to nursing mothers.

Storage

Store in a cool, dry place, away from direct sunlight. Keep out of reach of children.

Formulations

• Tablets
• Eye drops

Indications

• Ocular redness
• Nasal congestion
• Allergic rhinitis
• Conjunctival irritation

Dosage

Children: Refer to the BNF for Children for specific paediatric dosing recommendations.

Adults: Refer to the BNF for specific adult dosing recommendations.

Mechanism of action

Tetrahydrozoline selectively stimulates alpha-1 adrenergic receptors, which are G-protein-coupled receptors that regulate vascular tone. By activating these receptors, tetrahydrozoline induces vasoconstriction of the blood vessels in the nasal passages and conjunctival tissue, thereby reducing redness and congestion.

Pharmacodynamics

As a sympathomimetic amine, tetrahydrozoline possesses vasoconstricting and decongestant properties. It effectively constricts the smaller arterioles in the nasal and conjunctival blood vessels, alleviating symptoms of allergic rhinitis and ocular irritation. Additionally, tetrahydrozoline can cross the blood-brain barrier, where it may interact with alpha-2 adrenoceptors and imidazole receptors, potentially leading to effects such as hypotension, bradycardia, sedation, and analgesia.

Pharmacokinetics

Tetrahydrozoline is absorbed systemically and can be distributed throughout the body, including crossing the blood-brain barrier. The onset of action is typically rapid, with effects observed shortly after administration. The metabolism and excretion pathways are not extensively detailed in the available literature, hence specific pharmacokinetic parameters such as half-life and elimination pathways should be referenced from additional pharmacological sources.

Adverse effects

• Headache
• Dizziness
• Dry mouth
• Nausea
• Rebound congestion with prolonged use
• Increased intraocular pressure

Precautions

• Use with caution in patients with cardiovascular disease
• Use with caution in patients with hypertension
• Caution in patients with hyperthyroidism
• Caution in pregnant and breastfeeding women

Pregnancy

Tetrahydrozoline should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

It is not known whether tetrahydrozoline is excreted in human milk. Caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Ophthalmic solution
• Nasal spray

Mechanism of action

Antazoline binds to the histamine H1 receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine. Antihistamine drugs are competitive, reversible inhibitors of the action of histamine at the H1 receptor. /Antihistamines/

Pharmacodynamics

Antazoline is a histamine H1 receptor antagonist. It selectively bind to but does not activate histamine H1 receptors, thereby blocking the actions of endogenous histamine.

Mechanism of action

Adrenergic receptors are G-protein-coupled receptors (GPCR) that regulate vascular tone: stimulation of alpha-1 adrenergic receptors leads to vasoconstriction. Ocular redness and nasal congestion often result from vasodilation of nasal, conjunctival, and corneal capillary blood vessels. Activation of alpha-1 adrenergic receptors have been therefore associated with a reduction of symptoms of ocular irritation and nasal congestion. Tetryzoline is a selective agonist of alpha-1 adrenergic receptors, causing vasoconstriction and alleviating ocular and nasal symptoms.

Pharmacodynamics

Tetryzoline is a sympathomimetic amine and an alpha-adrenergic agonist with vasoconstricting and decongestant properties. It works by constricting the smaller arterioles of the nasal passages and conjunctival blood vessels to ameliorate allergic rhinitis, nasal congestion, and ocular irritation. Tetryzoline is known to cross the blood-brain barrier to work on alpha-2 adrenoceptors and imidazole receptors, causing effects like hypotension, bradycardia, analgesia, hypothermia, sedation, and hypnosis.