ACTIFED COLD TABLETS

Indications

• Nasal congestion due to colds
• Allergic rhinitis
• Sinusitis
• Eustachian tube congestion

Dosage

Children: Refer to specific guidelines or BNF for appropriate dosing recommendations.

Adults: Refer to specific guidelines or BNF for appropriate dosing recommendations.

Mechanism of action

Pseudoephedrine acts primarily as an agonist at adrenergic receptors, particularly alpha-1 adrenergic receptors. Its action leads to vasoconstriction of the nasal mucosa, reducing blood flow to the area, which in turn decreases edema and congestion. Additionally, it may stimulate beta-adrenergic receptors, which can lead to bronchodilation.

Pharmacodynamics

The pharmacodynamic effects of pseudoephedrine include its ability to promote nasal decongestion through vasoconstriction, resulting in a reduction of swelling in the nasal passages. It has a relatively low potency as a central nervous system stimulant compared to other sympathomimetics, which minimizes the risk of side effects such as insomnia or jitteriness.

Pharmacokinetics

Pseudoephedrine is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 1 to 2 hours after oral administration. It has a bioavailability of around 90%. The drug is metabolized in the liver, primarily by the cytochrome P450 system, and excreted in the urine. The elimination half-life is approximately 5 to 8 hours, which can be prolonged in patients with renal impairment.

Contra-indications

• Severe hypertension
• Severe coronary artery disease
• Concurrent use of monoamine oxidase inhibitors (MAOIs)
• Hypersensitivity to pseudoephedrine or any of its components

Adverse effects

• Insomnia
• Nervousness
• Dizziness
• Dry mouth
• Headache
• Increased blood pressure
• Tachycardia
• Nausea
• Vomiting

Interactions

• MAOIs may increase the risk of hypertensive crisis
• Other sympathomimetics may enhance side effects
• Antihypertensives may have reduced effectiveness
• Caffeine may increase the risk of adverse effects such as insomnia and jitteriness

Precautions

• Use with caution in patients with hypertension, diabetes, or hyperthyroidism
• May cause drowsiness; caution advised when driving or operating machinery
• Use with caution in patients with a history of cardiovascular disease

Pregnancy

Category C. Pseudoephedrine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Pseudoephedrine is excreted in breast milk. Caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• Tablets
• Extended-release tablets
• Liquid formulations

Indications

• Allergic rhinitis (hay fever)
• Allergic conjunctivitis
• Urticaria (hives)
• Other upper respiratory allergies

Dosage

Children: For children aged 2 to 6 years, the recommended dose is 1.25 mg to 2.5 mg taken

Adults: The usual adult dose for triprolidine is 2.5 mg to 5 mg taken orally, one to three times daily, as needed. Refer to the BNF for specific dosing recommendations.

Mechanism of action

Triprolidine binds to the histamine H1 receptor, inhibiting the action of endogenous histamine. By competing with histamine for H1-receptor sites on effector cells, it prevents the physiological responses mediated by histamine, such as pruritus, urticaria, and bronchoconstriction. The drug's anticholinergic effects also contribute to reduced secretion in the nasal mucosa.

Pharmacodynamics

In allergic reactions, allergens interact with surface IgE antibodies on mast cells, leading to degranulation and release of histamine. Histamine acts on H1-receptors to produce various effects, including itching, vasodilatation, and increased vascular permeability. Triprolidine, as an H1 antagonist, competes with histamine for receptor binding, effectively blocking these reactions and providing relief from allergy symptoms.

Pharmacokinetics

Triprolidine is absorbed well following oral administration, with peak plasma concentrations typically occurring within 2 to 4 hours. It has a relatively long half-life, allowing for sustained effects. The drug is metabolized in the liver and primarily excreted via urine. Due to its ability to cross the blood-brain barrier, triprolidine may also cause sedation as a side effect.

Adverse effects

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

Precautions

• Use with caution in patients with a history of glaucoma
• May exacerbate urinary retention in patients with prostatic hypertrophy
• Caution in driving or operating machinery due to sedative effects

Pregnancy

Triprolidine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult with a healthcare provider.

Breast-feeding

It is not known whether triprolidine is excreted in human milk. Caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Tablets
• Syrup

Mechanism of action

Triprolidine 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 used in the treatment of allergy act by competing with histamine for H1-receptor sites on effector cells. They thereby prevent, but do not reverse, responses mediated by histamine alone. Antihistamines antagonize, in varying degrees, most of the pharmacological effects of histamine, including urticaria and pruritus. Also, the anticholinergic actions of most antihistamines provide a drying effect on the nasal mucosa. /Antihistamines/ Antihistamines used in the treatment of allergy act by competing with histamine for H1-receptor sites on effector cells. They thereby prevent, but do not reverse, responses mediated by histamine alone. Antihistamines antagonize, in varying degrees, most of the pharmacological effects of histamine, including urticaria and pruritus. Also, the anticholinergic actions of most antihistamines provide a drying effect on the nasal mucosa. /Antihistamines/ H1 antagonists inhibit most responses of smooth muscle to histamine. Antagonism of the constrictor action of histamine on respiratory smooth muscle is easily shown in vivo and in vitro. /Histamine Antagonists: H1 Antagonists/ /SRP:/ The action of histamine results in increased permeability and formation of edema and wheal. H1 antagonists block that action. For more Mechanism of Action (Complete) data for TRIPROLIDINE (7 total), please visit the HSDB record page.

Pharmacodynamics

In allergic reactions an allergen interacts with and cross-links surface IgE antibodies on mast cells and basophils. Once the mast cell-antibody-antigen complex is formed, a complex series of events occurs that eventually leads to cell-degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil. Once released, histamine can react with local or widespread tissues through histamine receptors. Histamine, acting on H1-receptors, produces pruritis, vasodilatation, hypotension, flushing, headache, tachycardia, and bronchoconstriction. Histamine also increases vascular permeability and potentiates pain. Triprolidine, is a histamine H1 antagonist that competes with histamine for the normal H1-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies. Triprolidine has anticholinergic and sedative effects.