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# Bricanyl (Terbutaline) ## Overview Terbutaline is a selective $\beta_2$-adrenergic agonist that acts as a bronchodilator. While historically used for asthma, its use is now largely limited to emergency bronchodilation or, off-label, for tocolysis. Note: The FDA has issued a black box warning against the use of terbutaline for preterm labor due to serious maternal cardiac risks and death. ## Primary Indications - Acute reversible airway obstruction (asthma, COPD). - Off-label: Tocolysis (Acute management of preterm labor; discouraged due to safety risks). ## Adult Dosing - **Asthma/Bronchospasm (Subcutaneous):** 0.25 mg administered into the lateral deltoid area. May repeat once after 15–30 minutes if necessary. Do not exceed 0.5 mg in a 4-hour period. - **Tocolysis (Historical/Off-label):** Generally avoided; inpatient protocols vary highly. If used, typically 0.25 mg SC every 20 minutes to 3 hours, or IV infusion (highly variable by local institutional protocol). ## Pediatric Dosing - **Asthma (Subcutaneous):** 0.01 mg/kg/dose (max 0.25 mg per dose). May repeat every 15–20 minutes for two additional doses if needed, not to exceed 0.5 mg total in a 4-hour period. - **Safety Note:** Use with extreme caution; monitor for tachycardia. ## Dose Adjustments - **Renal Impairment:** Reduce dosage or increase frequency interval in patients with significant renal impairment, as terbutaline is primarily renally cleared. - **Hepatic Impairment:** No formal adjustment guidelines; monitor for increased sensitivity to sympathetic effects. ## Contraindications - Known hypersensitivity to terbutaline or any component of the formulation. - **For Tocolysis:** Cardiac arrhythmias, maternal heart disease, or conditions where tachycardia is hazardous. ## Adverse Effects - **Common:** Tachycardia, palpitations, tremors, nervousness, headache, dizziness. - **Serious:** Hypokalemia, hyperglycemia, pulmonary edema (high risk in tocolysis), arrhythmias, myocardial ischemia. ## Key Drug Interactions - **Beta-blockers:** May antagonize the effects of terbutaline. - **Diuretics (Loop/Thiazide):** Increased risk of hypokalemia; monitor potassium levels closely. - **MAOIs/Tricyclic Antidepressants:** May potentiate the pressor effects of terbutaline on the cardiovascular system. ## Monitoring - Heart rate and blood pressure (pre- and post-dose). - ECG/Telemetry if cardiac history or high-dose/IV use. - Potassium and glucose levels (especially with repeated dosing). - Respiratory status (symptom relief). ## Clinical Pearls - Selective $\beta_2$-agonist effect decreases as the dose increases, leading to increased $\beta_1$ (cardiac) stimulation. - Tremor is a common dose-limiting adverse effect but usually subsides with chronic use. - Inhaled short-acting $\beta_2$-agonists (e.g., albuterol) are generally preferred for asthma due to a better safety profile and local delivery. - Parenteral terbutaline should be avoided in pre-term labor unless no other therapeutic options exist and the benefit strongly outweighs the potential for maternal cardiac events. *** **Educational Disclaimer:** This information is for educational purposes only. Always verify drug dosages, contraindications, and clinical protocols against current institutional guidelines and the official manufacturer prescribing information (package insert) before prescribing or administering medication.