FLAMERGI STERILE EYE DROPS

Indications

• Nasal congestion
• Allergic rhinitis
• Ocular redness and irritation
• Sinusitis

Dosage

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

Adults: Refer to the BNF for specific dosing information.

Mechanism of action

Naphazoline is a vasoconstrictor that functions by stimulating alpha adrenergic receptors in arterioles, leading to decreased congestion at the site of administration. It causes the release of norepinephrine in sympathetic nerves, which binds to alpha adrenergic receptors and causes vasoconstriction. Additionally, naphazoline is a mild beta adrenergic receptor agonist, potentially resulting in rebound vasodilation after the alpha adrenergic stimulation has ceased. Its norepinephrine release triggers a negative feedback loop that reduces norepinephrine production, which can contribute to rhinitis medicamentosa upon cessation after prolonged use.

Pharmacodynamics

Naphazoline is a sympathomimetic alpha adrenergic agonist that acts to vasoconstrict nasal or ocular arterioles, resulting in reduced congestion at the site of administration. This property makes it effective in managing symptoms of nasal congestion and eye irritation.

Pharmacokinetics

The pharmacokinetics of naphazoline are characterized by its local action at the site of administration, with rapid onset of action. It undergoes systemic absorption; however, detailed pharmacokinetic parameters such as half-life, distribution volume, and elimination routes are not well documented in the provided sources.

Adverse effects

• Burning or stinging sensation in the nose or eyes
• Rebound congestion
• Increased blood pressure
• Tachycardia
• Headache
• Nausea

Precautions

• Use with caution in patients with cardiovascular disease
• Caution in patients with hypertension or hyperthyroidism
• Avoid prolonged use to prevent rhinitis medicamentosa

Pregnancy

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

Breast-feeding

Caution is advised when using naphazoline while breastfeeding.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Nasal spray
• Eye drops

Indications

• Allergic rhinitis
• Allergic conjunctivitis
• Urticaria
• Pruritus
• Common cold symptoms

Dosage

Children: For children aged 6 to 12 years, the recommended dose is 12.5 mg every 4 to 6 hours, not exceeding 75 mg in 24 hours. For children aged 2 to 6 years, consult the BNF for Children for appropriate dosing guidelines.

Adults: The usual oral dose for adults is 25 mg to 50 mg every 4 to 6 hours, not exceeding 300 mg in 24 hours.

Mechanism of action

Pheniramine competes with histamine for the histamine H1 receptor, acting as an inverse agonist once bound. This leads to reduced H1 receptor activity, which is responsible for alleviating symptoms such as itching, redness, and edema. Additionally, the inverse agonism of H4 receptors may contribute to its anti-inflammatory properties and further reduce itching.

Pharmacodynamics

Pheniramine antagonizes the effects of histamine, leading to decreased allergic symptoms such as edema, itching, and redness. Its central nervous system activity results in sedation, a characteristic effect of first-generation antihistamines. This dual action makes it effective for both allergy relief and as a mild sedative.

Pharmacokinetics

Pheniramine is absorbed well from the gastrointestinal tract and crosses the blood-brain barrier, leading to its sedative effects. The drug is extensively metabolized in the liver, and its metabolites are excreted primarily through the urine. The onset of action typically occurs within one hour, with a duration of effect lasting several hours.

Adverse effects

• Drowsiness
• Dizziness
• Dry mouth
• Blurred vision
• Constipation
• Urinary retention

Precautions

• Use with caution in patients with glaucoma
• Use with caution in patients with prostatic hypertrophy
• Caution in patients with cardiovascular disease
• May enhance the effects of alcohol and other CNS depressants

Pregnancy

Use only if clearly needed, as there are limited studies on safety.

Breast-feeding

Use with caution, as it may pass into breast milk and affect the infant.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Tablets
• Syrup

Mechanism of action

Naphazoline is a vasoconstrictor that functions by stimulating alpha adrenergic receptors in arterioles leading to decreased congestion at the site of administration. Naphazoline causes the release of norepinephrine in sympathetic nerves. Norepinephrine binds to alpha adrenergic receptors and causes vasoconstriction. Naphazoline is also a mild beta adrenergic receptor agonist, which can cause rebound vasodilation after the alpha adrenergic stimulation has ended. Naphazoline's release of norepinephrine also triggers a negative feedback loop which decreases production of norepinephrine, which can lead to rhinitis medicamentosa after long term use when naphazoline is stopped.

Pharmacodynamics

Naphazoline is a sympathomimetic alpha adrenergic agonist that acts to vasoconstrict nasal or ocular arterioles, resulting in reduced congestion at the site of administration.

Mechanism of action

Pheniramine competes with histamine for the histamine H1 receptor, acting as an inverse agonist once bound. The reduction in H1 receptor activity is responsible for reduced itching as well as reduced vasodilation and capillary leakage leading to less redness and edema. This can be seen in the suppression of the histamine-induced wheal (swelling) and flare (vasodilation) response. Inverse agonism of the H1 receptor in the CNS is also responsible for the sedation produced by first-generation antihistamines like pheniramine. The binding of pheniramine to H4 receptors, and subsequent inverse agonism, may also contribute to reduced itching by antagonizing inflammation.

Pharmacodynamics

Pheniramine acts as an antagonist to allergic symptoms stemming from inappropriate histamine release to reduce edema, itching, and redness. The same antihistamine effect also produces sedation by acting in the central nervous system.