BEXITROL HFA INHALATION AEROSOL

Indications

• Reversible airways obstruction in patients requiring long-term regular bronchodilator therapy
• Nocturnal asthma
• Chronic asthma in patients who regularly use an inhaled corticosteroid
• Prevention of exercise-induced bronchospasm

Dosage

Children: For children aged 5-11 years, the recommended dose is 50 micrograms twice daily. In

Adults: The typical adult dose is 50 micrograms twice daily, with the possibility of increasing to 100 micrograms twice daily in cases of more severe airway obstruction.

Mechanism of action

Salmeterol exerts its effects through stimulation of beta-2 adrenoceptors, causing relaxation of bronchial smooth muscle and bronchodilation. It binds to both the active site and an exo-site of the beta-2 adrenoceptor. The saligenin moiety attaches to the active site, while the hydrophilic tail interacts with leucine residues in the exo-site, leading to a prolonged action. Additionally, salmeterol inhibits the release of mast cell mediators and attenuates allergen-induced bronchial hyper-responsiveness.

Pharmacodynamics

As a long-acting beta-2 adrenergic receptor agonist, salmeterol has a longer duration of action compared to short-acting beta agonists like salbutamol. It enhances intracellular cAMP levels, which promotes smooth muscle relaxation. Patients should be aware of potential risks such as hypokalemia and hypoglycemia, and the importance of not using it as monotherapy for asthma management.

Pharmacokinetics

Salmeterol is administered via inhalation, with an onset of action within 15 minutes and a duration of effect lasting approximately 12 hours at recommended doses. It undergoes hepatic metabolism and is eliminated primarily via the feces. The pharmacokinetic profile allows for twice-daily dosing to maintain therapeutic effects.

Adverse effects

• Tachycardia
• Palpitations
• Tremors
• Headache
• Dizziness
• Nervousness
• Hypokalemia
• Hyperglycemia

Interactions

• cenobamate+salmeterol: Moderate (decreases exposure)
• cobicistat+salmeterol: Unknown (increases exposure)
• idelalisib+salmeterol: Unknown (increases exposure)

Precautions

• Use with caution in patients with cardiovascular disorders.
• Monitor for signs of hypokalemia, especially if used with diuretics.
• Not to be used as monotherapy for asthma; should be used with an inhaled corticosteroid.

Pregnancy

Salmeterol is classified as category C. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Salmeterol is excreted in breast milk. Use with caution, weighing the benefits against potential risks.

Storage

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

Formulations

• Inhalation powder - Serevent Accuhaler (50 micrograms per dose)
• Pressurised inhalation - Neovent (25 micrograms per dose)
• Pressurised inhalation - Serevent Evohaler (50 micrograms per dose)
• Inhalation powder - Soltel (25 micrograms per dose)

Indications

• Tinea pedis (athlete's foot)
• Tinea corporis (ringworm)
• Tinea cruris (jock itch)
• Onychomycosis (nail fungus)
• Candidiasis (fungal infections caused by Candida species)

Dosage

Children: For pediatric patients, refer to the BNF for Children for appropriate dosing guidelines based on age and weight.

Adults: For adults, refer to the specific product labeling and indications for use. Dosage may vary based on the formulation and site of infection.

Mechanism of action

Xinafoate primarily works by inhibiting the synthesis of ergosterol, an essential component of fungal cell membranes. By disrupting ergosterol production, xinafoate compromises the integrity of the fungal cell membrane, leading to cell lysis and death. This mechanism makes it effective against various dermatophytes and yeast species.

Pharmacodynamics

Xinafoate exerts its antifungal effects through the inhibition of fungal growth and reproduction. The drug demonstrates fungistatic and fungicidal properties depending on the concentration used. In lower concentrations, it may inhibit fungal growth, while at higher concentrations, it can kill the fungi. The onset of action can vary, but improvement in symptoms is generally observed within a few days of initiation of therapy.

Pharmacokinetics

Xinafoate is typically administered topically, leading to localized effects with minimal systemic absorption. Following topical application, it penetrates the stratum corneum and reaches the deeper layers of the skin where it exerts its antifungal action. The drug is metabolized in the liver, and its metabolites are excreted mainly via the urine. The half-life of xinafoate is not well-defined due to its topical application and limited systemic exposure.

Pregnancy

Xinafoate should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult a healthcare provider for individual assessment.

Breast-feeding

It is not known whether xinafoate is excreted in human breast milk. Caution should be exercised when administering to breastfeeding women.

Storage

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

Mechanism of action

Beta-2 adrenoceptor stimulation causes relaxation of bronchial smooth muscle, bronchodilation, and increased airflow. Salmeterol is hypothesized to bind to 2 sites on the beta-2 adrenoceptor. The saligenin moiety binds to the active site of the beta-2 adrenoceptor. The hydrophilic tail of salmeterol binds to leucine residues in the exo-site of the beta-2 adrenoceptor almost irreversibly, allowing salmeterol to persist in the active site, which is responsible for it's long duration of action. Another hypothesis is that the lipophilic drug diffuses into lipid bilayer of smooth muscle cells and provides a depot of drug to the cells over a longer period of time. In vitro tests show that salmeterol is a potent and long-lasting inhibitor of the release of mast cell mediators, such as histamine, leukotrienes, and prostaglandin D2, from human lung. Salmeterol inhibits histamine-induced plasma protein extravasation and inhibits platelet activating factor-induced eosinophil accumulation in the lungs of guinea pigs when administered by the inhaled route. In humans, single doses of salmeterol attenuate allergen-induced bronchial hyper-responsiveness. The pharmacologic effects of beta2-adrenoceptor agonist drugs, including salmeterol, are at least in part attributable to stimulation of intracellular adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3',5'-adenosine monophosphate (cyclic AMP). Increased cyclic AMP levels cause relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells. Salmeterol is a long-acting beta-adrenergic agonist. In vitro studies and in vivo pharmacologic studies demonstrate that salmeterol is selective for beta2-adrenoceptors compared with isoproterenol, which has approximately equal agonist activity on beta1- and beta2-adrenoceptors. In vitro studies show salmeterol to be at least 50 times more selective for beta2-adrenoceptors than albuterol. Although beta2-adrenoceptors are the predominant adrenergic receptors in bronchial smooth muscle and beta1-adrenoceptors are the predominant receptors in the heart, there are also beta2-adrenoceptors in the human heart comprising 10% to 50% of the total beta-adrenoceptors. The precise function of these is not yet established, but they raise the possibility that even highly selective beta2-agonists may have cardiac effects. Salmeterol ... membrane binding is non-competitive and dissociation is slow so that its effects last for many hours. Despite this, salmeterol does not accumulate in tissues. Its mechanism of action can be explained by binding to a specific exo-site domain of the beta 2-receptor protein to produce continuous stimulation of the active site of the receptor, which gives salmeterol a profile of pharmacological activity unlike that of other beta 2-agonists. Due to its potent and prolonged activation of beta 2-adrenoceptors in airway smooth muscle cells, endothelial cells, mast cells and epithelial cells, salmeterol induces prolonged bronchodilatation, reduced vascular permeability, inhibition of inflammatory mediators, stimulation of ciliary function and modulation of ion and water transport across the bronchial mucosa.

Pharmacodynamics

Salmeterol is a long acting beta-2 adrenergic receptor agonist that binds to both the active and exo sites of the beta-2 adrenergic receptor. Salmeterol has a longer duration of action than other beta-2 agonists like [salbutamol]. Patients should be counselled regarding the risks of long acting beta agonist (LABA) monotherapy, hypokalemia, hypoglycemia, and not to take this drug with another LABA.