WARNINGS
Deterioration of Asthma
Asthma may deteriorate acutely over a period of hours or chronically over several days or longer. If the patient needs more doses of terbutaline sulfate than usual, this may be a marker of destabilization of asthma and requires reevaluation of the patient and treatment regimen, giving special consideration to the possible need for anti-inflammatory treatment, e.g., corticosteroids.
Use of Anti-Inflammatory Agents
The use of beta-adrenergic agonist bronchodilators alone may not be adequate to control asthma in many patients. Early consideration should be given to adding anti-inflammatory agents, e.g., corticosteroids.
Cardiovascular Effects
Terbutaline sulfate, like all other beta-adrenergic agonists, can produce a clinically significant cardiovascular effect in some patients as measured by pulse rate, blood pressure, and/or symptoms. Although such effects are uncommon after administration of terbutaline sulfate at recommended doses, if they occur, the drug may need to be discontinued. In addition, beta-agonists have been reported to produce electrocardiogram (ECG) changes, such as flattening of the T wave, prolongation of the QTc interval, and ST segment depression. The clinical significance of these findings is unknown. Therefore, terbutaline sulfate, like all sympathomimetic amines, should be used with caution in patients with cardiovascular disorders, especially coronary insufficiency, cardiac arrhythmias, and hypertension.
Seizures
There have been rare reports of seizures in patients receiving terbutaline; seizures did not recur in these patients after the drug was discontinued.
PRECAUTIONS
Tocolysis
Terbutaline sulfate has not been approved and should not be used for tocolysis. Serious adverse reactions may occur after administration of terbutaline sulfate to women in labor. In the mother, these include increased heart rate, transient hyperglycemia, hypokalemia, cardiac arrhythmias, pulmonary edema, and myocardial ischemia. Increased fetal heart rate and neonatal hypoglycemia may occur as a result of maternal administration.
General
Terbutaline, as with all sympathomimetic amines, should be used with caution in patients with cardiovascular disorders, including ischemic heart disease, hypertension, and cardiac arrhythmias; in patients with hyperthyroidism or diabetes mellitus; and in patients who are unusually responsive to sympathomimetic amines or who have convulsive disorders. Significant changes in systolic and diastolic blood pressure have been seen and could be expected to occur in some patients after use of any beta-adrenergic bronchodilator.
Immediate hypersensitivity reactions and exacerbations of bronchospasm have been reported after terbutaline administration.
Beta-adrenergic agonist medications may produce significant hypokalemia in some patients, possibly through intracellular shunting, which has the potential to produce adverse cardiovascular effects. The decrease is usually transient, not requiring supplementation.
Large doses of intravenous terbutaline have been reported to aggravate pre-existing diabetes mellitus and ketoacidosis.
Drug Interactions
The concomitant use of terbutaline sulfate injection with other sympathomimetic agents is not recommended, since the combined effect on the cardiovascular system may be deleterious to the patient.
Monoamine 0xidase Inhibitors or Tricyclic Antidepressants:
Terbutaline should be administered with extreme caution to patients being treated with monoamine oxidase inhibitors or tricyclic antidepressants, or within 2 weeks of discontinuation of such agents, since the action of terbutaline on the vascular system may be potentiated.
Beta-Blockers:
Beta-adrenergic receptor blocking agents not only block the pulmonary effect of beta-agonists, such as terbutaline sulfate injection, but may produce severe bronchospasm in asthmatic patients. Therefore, patients with asthma should not normally be treated with beta-blockers. However, under certain circumstances, e.g., as prophylaxis after myocardial infarction, there may be no acceptable alternatives to the use of beta-adrenergic blocking agents in patients with asthma. In this setting, cardioselective beta-blockers could be considered, although they should be administered with caution.
Diuretics:
The ECG changes and/or hypokalemia that may result from the administration of nonpotassium-sparing diuretics (such as loop or thiazide diuretics) can be acutely worsened by beta-agonists, especially when the recommended dose of the beta-agonist is exceeded. Although the clinical significance of these effects is not known, caution is advised in the coadministration of beta-agonists with nonpotassium-sparing diuretics.
Carcinogenesis, Mutagenesis, Impairment of Fertility
In a 2-year study in Sprague-Dawley rats, terbutaline sulfate caused a significant and dose-related increase in the incidence of benign leiomyomas of the mesovarium at dietary doses of 50 mg/kg and above (approximately 810 times the maximum recommended daily subcutaneous (sc) dose for adults on a mg/m2 basis). In a 21-month study in CD-1 mice, terbutaline sulfate showed no evidence of tumorigenicity at dietary doses up to 200 mg/kg (approximately 1,600 times the maximum recommended daily sc dose for adults on a mg/m2 basis). The mutagenicity potential of terbutaline sulfate has not been determined.
Reproduction studies in rats using terbutaline sulfate demonstrated no impairment of fertility at oral doses up to 50 mg/kg (approximately 810 times the maximum recommended daily sc dose for adults on a mg/m2 basis).
Pregnancy
Teratogenic Effects; Pregnancy Category B
A reproduction study in Sprague-Dawley rats revealed terbutaline sulfate was not teratogenic when administered orally at doses up to 50 mg/kg (approximately 810 times the maximum recommended daily sc dose for adults on a mg/m2 basis). A reproduction study in New Zealand white rabbits revealed terbutaline sulfate was not teratogenic when administered orally at doses up to 50 mg/kg (approximately 1,600 times the maximum recommended daily sc dose for adults on a mg/m2 basis).
There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human responses, terbutaline sulfate injection should be used during pregnancy only if the potential benefits justify the potential risk to the fetus.
Use In Labor and Delivery
Because of the potential for beta-agonist interference with uterine contractility, use of terbutaline sulfate injection for relief of bronchospasm during labor should be restricted to those patients in whom the benefits clearly outweigh the risk.
Terbutaline crosses the placenta. After single dose IV administration of terbutaline to 22 women in late pregnancy who were delivered by elective Cesarean section due to clinical reasons, umbilical blood levels of terbutaline were found to range from 11% to 48% of the maternal blood levels.
Nursing Mothers
It is not known whether this drug is excreted in human milk. Therefore, terbutaline sulfate injection should be used during nursing only if the potential benefit justifies the possible risk to the newborn.
Pediatric Use
Terbutaline sulfate injection is not recommended for patients under the age of 12 years because of insufficient clinical data to establish safety and effectiveness.
Geriatric Use
Clinical studies of terbutaline sulfate injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
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