Brethine Side Effects

Generic name: terbutaline

Note: This document contains side effect information about terbutaline. Some of the dosage forms listed on this page may not apply to the brand name Brethine.

Some side effects of Brethine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to terbutaline: oral tablet

Stop taking terbutaline (the active ingredient contained in Brethine) and seek emergency medical attention if you experience any of the following serious side effects:

• an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives); or

• chest pain or irregular heartbeats.

Other, less serious side effects may be more likely to occur. Continue to take terbutaline and talk to your doctor if you experience

• headache;

• dizziness or lightheadedness;

• insomnia;

• tremor or nervousness;

• sweating;

• nausea, vomiting, or diarrhea; or

• dry mouth.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

Applies to terbutaline: compounding powder, inhalation aerosol, inhalation aerosol with adapter, injectable solution, oral tablet

General

Terbutaline has usually been well tolerated and adverse effects seen have been consistent with its pharmacological action. In general, the severity of these adverse effects have been dependent on dose and the route of administration. Administration by metered dose inhaler (MDI) has been associated with less systemic effects than administration of higher doses by nebulizer or orally. Tolerance to the adverse effects of terbutaline (the active ingredient contained in Brethine) has occurred.

Cardiovascular

Changes in heart rate of approximately 30% may be observed following 5 mg of terbutaline (the active ingredient contained in Brethine) given orally. Aggravation of angina may be due to the tachycardia induced by terbutaline. Prolongation of the QT interval occurred in ten healthy males given a bolus injection of 0.25 mg terbutaline followed by an infusion of 5 mcg/min. Supraventricular ectopic beats and ventricular tachycardia have also been reported. Higher dosages of terbutaline should be used with caution in patients with cardiac disease, arrhythmias, or hypertension. All of these effects are dose-related and lower doses may be tolerated.

In one case-control study a positive association was found between the use of oral terbutaline for longer than 9 days and peripartum cardiomyopathy. Further study is needed to determine if a causative relationship exists.

Cardiovascular side effects have included palpitations and peripheral vasodilation, commonly resulting in reflex tachycardia. Changes in blood pressure, both increases and decreases, have been reported. Higher dosages have rarely aggravated angina and myocardial ischemia or caused atrial or ventricular arrhythmias. Rarely, peripartum cardiomyopathy has been reported with oral therapy. Pulmonary edema has occurred in pregnant patients receiving intravenous terbutaline.

Musculoskeletal

Musculoskeletal side effects have included tremors, especially at higher doses. Tolerance has developed to the tremorogenic effects. Severe muscle cramping has been rarely reported.

Metabolic

Metabolic side effects have included hypokalemia, hypomagnesemia, and less commonly hyperglycemia.

Infusions of terbutaline, 25 mcg/min, in women in premature labor has caused decreases in serum potassium of up to 1.6 to 2 mEq/L. Another study in ten healthy males produced a mean decrease in serum potassium of 0.9 mEq/L following a bolus injection of 0.25 mg terbutaline, followed by an infusion of 5 mcg/min. A decrease in magnesium of 0.08 mmol/L was produced in these same patients.

This fall in potassium is presumably due to an intracellular shift of potassium secondary to hyperglycemia and hyperinsulinemia.

Nervous system

Nervous system side effects have included headache, restlessness, anxiety, nervousness, irritability, and insomnia.

Other

Other side effects have included the development of tachyphylaxis to the bronchodilating effects of terbutaline (the active ingredient contained in Brethine) Although conflicting data exist, the development of complete tolerance has not been reported.

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