Terbutaline for Asthma

INDICATIONS AND USAGE Terbutaline Sulfate Injection, USP is 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.

DOSAGE AND ADMINISTRATION Adults The usual oral dose of terbutaline sulfate for adults is 5 mg administered at approximately six-hour intervals, three times daily, during the hours the patient is usually awake. If side effects are particularly disturbing, the dose may be reduced to 2.5 mg three times daily, and still provide a clinically significant improvement in pulmonary function. The total dose within 24 hours should not exceed 15 mg. Children Terbutaline sulfate is not recommended for use in children below the age of 12 years. A dosage of 2.5 mg three times daily is recommended for children 12 to 15 years of age. The total dose within 24 hours should not exceed 7.5 mg. If a previously effective dosage regimen fails to provide the usual relief, medical advice should be sought immediately as this is often a sign of seriously worsening asthma that would require reassessment of therapy.

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 the 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.

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 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.

ADVERSE REACTIONS Adverse reactions observed with terbutaline are similar to those commonly seen with other sympathomimetic agents. All these reactions are transient in nature and usually do not require treatment. The following table compares adverse reactions seen in patients treated with terbutaline (0.25 mg and 0.5 mg), with those seen in patients treated with epinephrine injection (0.25 mg and 0.5 mg), during eight double-blind crossover studies involving a total of 214 patients. Incidence (%) of Adverse Reactions Terbutaline (%) Terbutaline (%) 0.25 mg N=77 0.5 mg N=205 Reaction Central Nervous System Tremor 7.8 38 Nervousness 16.9 30.7 Dizziness 1.3 10.2 Headache 7.8 8.8 Drowsiness 11.7 9.8 Cardiovascular Palpitations 7.8 22.9 Tachycardia 1.3 1.5 Respiratory Dyspnea 0 2 Chest discomfort 1.3 1.5 Gastrointestinal Nausea/vomiting 1.3 3.9 Systemic Weakness 1.3 0.5 Flushed feeling 0 2.4 Sweating 0 2.5 Pain at injection site 2.6 0.5 Epinephrine (%) Epinephrine (%) 0.25 mg N=153 0.5 mg N=61 Reaction Central Nervous System Tremor 16.3 18 Nervousness 8.5 31.1 Dizziness 7.8 3.3 Headache 3.3 9.8 Drowsiness 14.4 8.2 Cardiovascular Palpitations 7.8 29.5 Tachycardia 2.6 0 Respiratory Dyspnea 2 0 Chest discomfort 2.6 0 Gastrointestinal Nausea/vomiting 1.3 11.5 Systemic Weakness 2.6 1.6 Flushed feeling 1.3 0 Sweating 0 0 Pain at injection site 2.6 1.6 Note: Some patients received more than one dosage strength of terbutaline and epinephrine. In addition, there were reports of anxiety, muscle cramps, and dry mouth (less than 0.5%). There have been rare reports of elevations in liver enzymes and of hypersensitivity vasculitis with terbutaline administration.