Muco-Asthalin Syrup

Indications

• Bronchospasm
• Asthma
• Chronic bronchitis
• Emphysema

Dosage

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

Adults: Refer to the BNF for specific dosing guidelines.

Mechanism of action

Terbutaline exerts its effects through selective agonism of beta-2 adrenergic receptors located in the bronchioles. This activation leads to the stimulation of adenylyl cyclase, which increases the levels of intracellular cyclic adenosine monophosphate (cAMP). The rise in cAMP reduces intracellular calcium concentrations, leading to the activation of protein kinase A. This enzyme inactivates myosin light-chain kinase and activates myosin light-chain phosphatase, ultimately resulting in the relaxation of smooth muscle within the bronchioles.

Pharmacodynamics

As a beta-2 adrenergic receptor agonist, terbutaline is indicated for the relief of bronchospasm in conditions such as asthma, chronic bronchitis, and emphysema. It has a rapid onset of action and a relatively short duration of effect, typically requiring administration up to three times daily in its inhaled form. The therapeutic window for terbutaline is wide, making it generally safe within prescribed doses.

Pharmacokinetics

Terbutaline is rapidly absorbed when administered via inhalation, allowing for quick therapeutic action. The drug undergoes extensive first-pass metabolism when taken orally, which may affect its bioavailability. It is primarily metabolized in the liver and has a half-life that supports frequent dosing. Excretion occurs mainly via the kidneys, with metabolites detectable in urine.

Contra-indications

• Hypersensitivity to terbutaline or any of its components
• Severe hypersensitivity to sympathomimetic amines
• Tachyarrhythmias
• Cardiac arrhythmias

Adverse effects

• Tremor
• Tachycardia
• Palpitations
• Headache
• Nausea
• Dizziness
• Muscle cramps
• Hypokalemia

Interactions

• Beta-blockers may reduce the effectiveness of terbutaline
• Concomitant use with other sympathomimetics may increase the risk of cardiovascular side effects
• Monoamine oxidase inhibitors (MAOIs) can potentiate the effects of terbutaline

Precautions

• Use with caution in patients with cardiovascular disorders
• Monitor potassium levels in patients with significant hypokalemia
• Caution in patients with diabetes mellitus as beta agonists may induce hyperglycemia

Pregnancy

Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. Category C.

Breast-feeding

Terbutaline is excreted in human milk, and caution should be exercised when administered to a nursing woman.

Storage

Store below 25 degrees Celsius. Protect from light and moisture. Keep out of reach of children.

Formulations

• Inhalation aerosol
• Oral tablets
• Injection

Indications

• Asthma
• Chronic Obstructive Pulmonary Disease (COPD)
• Exacerbation of reversible airways obstruction
• Prevention of exercise-induced bronchospasm
• Uncomplicated premature labor (under specialist supervision)

Dosage

Adults: Initially 2.5 mg 3 times a day for 1–2 weeks, then increased to

Mechanism of action

Terbutaline exerts its effects by selectively stimulating beta-2 adrenergic receptors located in the smooth muscle of the airways. This activation leads to the activation of adenylate cyclase, resulting in increased levels of cyclic AMP (cAMP). Elevated cAMP levels promote relaxation of the bronchial smooth muscle, leading to bronchodilation. Additionally, terbutaline may inhibit the release of mediators from mast cells, reducing bronchoconstriction and inflammation.

Pharmacodynamics

The pharmacodynamic profile of terbutaline includes rapid onset of action, typically within 5 to 15 minutes when inhaled, and a duration of action of approximately 3 to 6 hours. It provides symptomatic relief from bronchospasm associated with asthma and chronic obstructive pulmonary disease (COPD). The drug is also noted for its tocolytic effects, as it can inhibit uterine contractions, making it useful in managing premature labor.

Pharmacokinetics

Terbutaline is well absorbed following inhalation and oral administration, with peak plasma concentrations occurring within 1 to 3 hours. It exhibits a volume of distribution of approximately 3 L/kg, indicating extensive tissue distribution. The drug is metabolized primarily in the liver and has a half-life of about 3 to 5 hours. Terbutaline is excreted mainly in urine, both as unchanged drug and metabolites. Its pharmacokinetic profile may be affected by factors such as age, liver function, and concomitant medications.

Adverse effects

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

Interactions

• Beta-blockers may reduce the effectiveness of terbutaline
• Corticosteroids may enhance the effect of terbutaline
• Concomitant use with other sympathomimetics may increase cardiovascular side effects

Precautions

• Use with caution in patients with cardiovascular disorders
• Caution in patients with diabetes due to potential hyperglycemia
• Monitor potassium levels in patients at risk of hypokalemia
• Monitor for paradoxical bronchospasm

Pregnancy

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

Breast-feeding

Terbutaline is excreted in breast milk; 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: 2.5 mg and 5 mg
• Nebuliser solution: 0.5 mg/ml
• Injection: 0.5 mg/1 ml

Mechanism of action

Terbutaline is a selective beta-2 adrenergic receptor agonist. Agonism of these receptors in bronchioles activates adenylyl cyclase, increasing intracellular cyclic adenosine monophosphate (cAMP). Increased cAMP decreases intracellular calcium, activating protein kinase A, inactivating myosin light-chain kinase, activating myosin light-chain phosphatase, and finally relaxing smooth muscle in the bronchiole.

Pharmacodynamics

Terbutaline is a beta-2 adrenergic receptor agonist indicated to treat reversibly bronchospasm in asthmatic patients with bronchitis and emphysema. It has a short duration as the inhaled form is taken up to three times daily, and the therapeutic window is wide.