Oral
Acute bronchospasm
Inhalation
Acute bronchospasm
Intravenous
Inhalation
Dosage/Direction for Use
Oral Acute bronchospasm Inhalation Acute bronchospasm Intravenous Inhalation |
Administration
May be taken with or without food.
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Contraindications
Parenteral: Prolonged (beyond 48-72 hr) or maintenance tocolysis, particularly in outpatient or home setting. PO: Acute or maintenance tocolysis.
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Special Precautions
Patient w/ thyrotoxicosis, HTN, DM, ketoacidosis, CV disorders (e.g. ischaemic heart disease), convulsive disorders, coronary insufficiency or associated arrhythmias. Childn. Pregnancy and lactation. Monitoring Parameters Monitor cardiorespiratory function, serum K and glucose levels; signs/symptoms of pulmonary oedema (when used in premature labour).
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Adverse Reactions
Tachycardia, nervousness, tremor, palpitations, dizziness, headache, nausea, vomiting, anxiety, restlessness, lethargy, drowsiness, weakness, flushes, sweating, chest discomfort, muscle cramps, tinnitus. Rarely, seizures, hypersensitivity vasculitis, elevated liver enzymes.
Potentially Fatal: Increased heart rate, transient hyperglycaemia, hypokalaemia, cardiac arrhythmias, pulmonary oedema, myocardial ischaemia. |
Overdosage
Symptoms: Headache, anxiety, tremor, nausea, tonic cramps, palpitations, tachycardia, arrhythmia; hypotension, hypokalaemia, hyperglycaemia and lactic acidosis may occur. Management: Reduce dose in mild to moderate cases. In severe cases, perform necessary tests to determine acid-base balance, blood sugar and electrolyte levels. Monitor BP, heart rate and rhythm and correct metabolic changes. A cardioselective β-blocker (e.g. metoprolol) may be given for the treatment of arrhythmias but w/ caution.
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Drug Interactions
Increased risk of haemorrhage and serious ventricular rhythm disorder w/ halogenated anaesth. May reduce the effect of anti-diabetic drugs. Increased risk of hypokalaemia w/ K-depleting agents (e.g. diuretics). Concomitant β-agonist and corticosteroid may result to pulmonary oedema. May partially or totally inhibit the effect of non-selective β-blockers.
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Action
Terbutaline stimulates intracellular adenyl cyclase, the enzyme that catalyses the conversion of ATP to cyclic-3?, 5?-adenosine monophosphate (cAMP) resulting in relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from mast cells.
Onset: W/in 5 min (inhalation); 30-45 min (oral); 6-15 min (SC). Duration: 6 hr (inhalation); 8 hr (oral). Absorption: Variably absorbed from the GI tract (approx 30-50%); absorbed from the airways (<10%); well absorbed following SC admin. Bioavailability: Approx 14-15% (oral). Time to peak plasma concentration: 1-4 hr. Distribution: Crosses the placenta and enters breast milk (trace amounts). Plasma protein binding: 25%. Metabolism: Undergoes extensive first-pass metabolism via sulfate and some glucoronide conjugation in the liver and the gut wall. Excretion: Via urine and faeces as inactive sulfate conjugate and unchanged drug. Terminal half-life: 16-20 hr. |
Storage
Inhalation: Store between 20-25°C. Protect from light. Intravenous: Store between 20-25°C. Protect from light. Oral: Store between 20-25°C. Protect from light. Parenteral: Store between 20-25°C. Protect from light.
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ATC Classification
R03AC03 - terbutaline ; Belongs to the class of adrenergic inhalants, selective beta-2-adrenoreceptor agonists. Used in the treatment of obstructive airway diseases.
R03CC03 - terbutaline ; Belongs to the class of adrenergics for systemic use, selective beta-2-adrenoreceptor agonists. Used in the treatment of obstructive airway diseases. |