terbutaline sulfate Brethine, Bricanyl
Pharmacologic classification: adrenergic (beta2 agonist) Therapeutic classification: bronchodilator, premature labor inhibitor (tocolytic) Pregnancy risk category B
Available forms Available by prescription only Injection: 1 mg/ml parenteral Tablets: 2.5 mg, 5 mg
Indications and dosages Relief of bronchospasm in patients with reversible obstructive airway disease. Adults and adolescents age 15 and older: 5 mg P.O. t.i.d. at 6-hour intervals. Reduce dosage to 2.5 mg P.O. t.i.d. if adverse effects occur. Maximum dosage is 15
mg daily. Or, 0.25 mg S.C. may be repeated in 15 to 30 minutes. Maximum dosage is 0.5 mg q 4 hours. Children ages 12 to 15: 2.5 mg P.O. t.i.d. Maximum dosage is 7.5 mg daily. Premature labor ◇. Adults: Initially, 2.5 to 10 mcg/ minute I.V. Increase dose gradually as tolerated at 10- to 20-minute intervals until desired effects
are achieved. Maximum dosages range from 17.5 to 30 mcg/minute, although dosages up to 80 mcg/minute have been used cautiously.
Continue infusion for at least 12 hours after uterine contractions stop. Maintenance therapy is 2.5 to 10 mg P.O. q 4 to 6
hours.
Pharmacodynamics Bronchodilator action: Terbutaline acts directly on beta2-adrenergic receptors to relax bronchial smooth muscle, relieving bronchospasm and reducing airway resistance. Cardiac and
CNS stimulation may occur with high doses. Tocolytic action: When used in premature labor, terbutaline relaxes uterine smooth muscle, which inhibits uterine contractions.
Pharmacokinetics Absorption: About 33% to 50% of an oral dose is absorbed through the GI tract. Distribution: Distributed widely throughout the body. Metabolism: Partially metabolized in the liver to inactive compounds. Excretion: After parenteral administration, 60% of drug is excreted unchanged in urine, 3% in feces through bile, and the remainder
in urine as metabolites. After oral administration, most drug is excreted as metabolites.
Route |
Onset |
Peak |
Duration |
P.O. |
1/2 hr |
2-3 hr |
4-8 hr |
S.C. |
15 min |
1/2 hr |
1 1/2-4 hr |
|
Contraindications and precautions Contraindicated in patients hypersensitive to drug or sympathomimetic amines. Use cautiously in patients with CV disorders,
hyperthyroidism, diabetes, or seizure disorders.
Interactions Drug-drug. Cardiac glycosides, cyclopropane, halogenated inhaled anesthetics, levodopa: Increases risk of arrhythmias. Monitor patient closely. Avoid use with levodopa. CNS stimulants: Increases CNS stimulation. Avoid use together. MAO inhibitors: May cause hypertensive crisis. Avoid use together. Propranolol, other beta blockers: Blocks bronchodilation effects of terbutaline. Avoid use together. Sympathomimetics: May cause additive adverse CV effects. Don’t use together.
Adverse reactions CNS: nervousness, tremor, drowsiness, dizziness, headache, weakness. CV: palpitations, tachycardia, arrhythmias, flushing. GI: vomiting, nausea, heartburn. Metabolic: hypokalemia. Respiratory: paradoxical bronchospasm with prolonged use, dyspnea. Skin: diaphoresis.
Effects on lab test results May decrease potassium levels.
Overdose and treatment Signs and symptoms of overdose include exaggeration of common adverse reactions, particularly arrhythmias, seizures, nausea,
and vomiting. Treatment requires supportive measures. If patient is conscious and ingestion was recent, induce emesis and follow with gastric
lavage. If patient is comatose, after endotracheal tube is in place with cuff inflated, perform gastric lavage; then administer
activated charcoal to reduce drug absorption. Maintain adequate airway, provide cardiac and respiratory support, and monitor
vital signs closely.
Special considerations ALERT Don’t confuse terbutaline with terbinafine. Store injection solution away from light. Don’t use if discolored. CV effects are more likely with S.C. route and when patient has arrhythmias. Most adverse reactions are transient; however, tachycardia may persist for a relatively long time. Terbutaline may reduce the sensitivity of spirometry for diagnosis of bronchospasm. Carefully monitor patient for toxicity. When drug is used for tocolytic therapy, monitor patient for CV effects, including tachycardia, for 12 hours after discontinuation
of drug. Monitor intake and output; fluid restriction may be needed. Muscle tremor is common but may subside with continued
use. Monitor neonate for hypoglycemia if the mother used terbutaline during pregnancy. Pregnant patients Manufacturers state that drug shouldn’t be used to treat preterm labor. Use drug during pregnancy only when expected benefits
justify risk to fetus. Breast-feeding patients Drug appears in breast milk in minute amounts. Use cautiously in breast-feeding women. Pediatric patients Drug isn’t recommended for use in children younger than age 12. Geriatric patients These patients are more sensitive to the effects of terbutaline; a lower dose may be required.
Patient education Instruct patient to use terbutaline only as directed and to call promptly if drug produces no relief or if condition worsens.
Advise patient to take a missed dose within 1 hour. If missed dose is remembered more than 1 hour later, patient should skip
the dose. Caution patient that many OTC cold and allergy remedies contain a sympathomimetic that may be harmful when combined with terbutaline.
Reactions may be common, uncommon, life-threatening, or
COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use
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