Indicated for the prevention and reversal of bronchospasm in patients 12 years of age and older with asthma and reversible bronchospasm associated with bronchitis and emphysema.
Beta-2 Agonist; Antiasthmatic
Terbutaline is a relatively selective β2-adrenergic bronchodilator that has little or no effect on alpha-adrenergic receptors. The drug has exerts a preferential effect on β2-adrenergic receptors but stimulates beta-adrenergic receptors less selectively than relatively selective β2-agonists. Terbutaline appears to have a greater stimulating effect on beta-receptors of the bronchial, vascular, and uterine smooth muscles (β2 receptors) than on the beta-receptors of the heart (β1 receptors). This drug relaxes smooth muscle and inhibits uterine contractions, but may also cause some cardiostimulatory effects and CNS stimulation.
The pharmacologic effects of terbutaline are at least in part attributable to stimulation through beta-adrenergic receptors of intracellular adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic- 3',5'- adenosine monophosphate (c-AMP). Increased c-AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells.
ORAL Acute bronchospasm: Adult: Initially, 2.5 or 3 mg tid increased to 5 mg tid if necessary; as modified-release tablet: 7.5 mg bid. Child: 75 mcg/kg tid; usual dose for >7 yr: 2.5 mg bid-tid. INHALATION Acute bronchospasm: Adult: As metered dose inhaler: 250 mcg or 500 mcg every 4-6 hrs. Max: 2000 mcg/24hr. As nebuliser: 5-10 mg inhaled 2-4 times or 1-2mg/hr given as a 0.0 1% nebuliser soln in Na Cl 0.9%. Child: As metered dose inhaler: 250 mcg or 500 mcg every 4-6 hrs. Max: 2000 mcg/24hr. As nebuliser: 2-5 mg inhaled 2-4 times. PARENTERAL Severe bronchospasm: Adult: 250-500 mcg SC, IM or slow IV lnj up to 4 times daily, or by IV infusion 3-5 mcg/ml run at a infusion rate of 0.5-1 mL/min. Child: >2 yrs: 10 mcg/ kg by SC, IM or slow IV injection. Max total dose: 300mcg.
β-blocking agents, especially the non-selective ones such as propranolol may partially or totally inhibit the effect of β-stimulants. Therefore Terbutaline preparations and non-selective β-blockers should not normally be administered concurrently. Terbutaline should be used with caution in patients receiving other sympathomimetics.
Hypersensitivity to sympathomimetics. Any condition of mother or foetus in which prolongation of pregnancy is dangerous. Arrhythmias, hyperthyroidism, hypertension, diabetes, myocardial Insufficiency, history of seizures, heart disease.
Fine skeletal muscle tremor esp hands, dizziness, anxiety, flushes, sweating, nausea, vomiting, lethargy, tinnitus, tachycardia, palpitations, muscle cramps, headache, paradoxical bronchospasm. IV: Transient hyperglycemia, transient hypokaelemia. (IV): Ml, pulmonary oedema, ketoacidosis.
This drug should be used during pregnancy only if the benefit outweighs the risk to the fetus. Although this drug is secreted into breast milk and milk concentrations are approximately those in maternal plasma, two individual case studies indicate that the infant is likely to receive 0.2-0.7% of the maternal dose, depending on the time of feeding in relation to administration of the drug. No signs of beta-adrenoceptor stimulation were observed. Use only if the expected benefit to mother outweigh risk to the infant.
Possible symptoms: Headache, anxiety, tremor, tonic cramp, palpitations, arrhythmia. A fall in blood pressure sometimes occurs.
Treatment:
Mild and moderate cases: Reduce the dose.
Severe cases: Gastric lavage, administration of activated charcoal.
Store in a cool and dry place, protected from light.
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