Terbutaline

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 Oxidase 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 betablockers 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.

Pregnancy -Teratogenic Effects There are no adequate and well-controlled studies of terbutaline sulfate in pregnant women. Published animal studies show that rat offspring exhibit alterations in behavior and brain development, including decreased cellular proliferation and differentiation when dams were treated subcutaneously with terbutaline during the late stage of pregnancy and lactation period. Terbutaline exposures in rat dams were approximately 24 to 48 times the common human dose in adults of 2-4 mg/day, on a mg/m 2 basis. Terbutaline sulfate has not been approved and should not be used for prolonged tocolysis (beyond 48-72 hours).

In particular, terbutaline sulfate should not be used for maintenance tocolysis in the outpatient or home setting. Serious adverse reactions, including death, have been reported after administration of terbutaline sulfate to pregnant women. In the mother, these adverse reactions 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 (see BOXED WARNING: Prolonged Tocolysis and CONTRAINDICATIONS: Prolonged Tocolysis ).

In animal embryofetal developmental studies, no teratogenic effects were observed in offspring when pregnant rats and rabbits received terbutaline sulfate at oral doses up to 50 mg/kg/day, approximately 810 and 1,600 times, respectively, the maximum recommended daily subcutaneous dose for adults, on a mg/m 2 basis. Terbutaline sulfate should be used during pregnancy only if the potential benefits justify the potential risk to the fetus.

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.