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# Bricanyl (Terbutaline)
## Overview
Terbutaline is a selective beta-2 adrenergic agonist. It acts as a bronchodilator by stimulating adenyl cyclase, increasing intracellular cyclic AMP (cAMP) levels, which results in bronchial smooth muscle relaxation. It also possesses tocolytic properties, though its use for preterm labor is no longer recommended by the FDA due to serious maternal and fetal safety risks.
## Primary Indications
* Acute bronchospasm (Asthma, COPD).
* *Off-label/Historical:* Inhibition of preterm labor (not recommended due to safety profile).
## Adult Dosing
* **Subcutaneous (SQ):** 0.25 mg injected 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.
* **Oral (Historical/Limited use):** 2.5 to 5.0 mg three times daily, at 6-hour intervals. Maximum dose: 15 mg/day.
## Pediatric Dosing
* **SQ (ages 12 years and older):** 0.25 mg as a single dose. May repeat once after 15–30 minutes.
* **Note:** Routine use in children under 12 years is generally not recommended or lacks robust supportive data; dosing is often weight-based at 0.005–0.01 mg/kg (max 0.25 mg) per dose if used, but local protocols vary significantly.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Terbutaline is primarily excreted renally; lower doses or increased intervals may be required in severe impairment.
* **Hepatic Impairment:** No specific guidelines; use caution and monitor for systemic effects.
## Contraindications
* Known hypersensitivity to terbutaline or any component of the formulation.
* Use for prolonged tocolysis (>48–72 hours).
## Adverse Effects
* **Common:** Tremor (especially in hands), tachycardia, palpitations, nervousness, dizziness, headache.
* **Serious:** Hypokalemia, hyperglycemia, cardiac arrhythmias, myocardial ischemia, pulmonary edema (noted particularly in pregnancy).
## Key Drug Interactions
* **Beta-blockers:** May antagonize the therapeutic effect of terbutaline.
* **Diuretics (loop/thiazide):** May potentiate the risk of hypokalemia induced by beta-agonists.
* **MAO Inhibitors / TCAs:** May potentiate the effects of terbutaline on the vascular system.
* **Sympathomimetics:** May lead to additive cardiac stimulation.
## Monitoring
* **Respiratory:** Monitor lung sounds, oxygen saturation, and respiratory rate before and after administration.
* **Cardiac:** Monitor pulse and blood pressure; observe for arrhythmias.
* **Labs:** Potassium (risk of hypokalemia) and glucose (risk of hyperglycemia) in patients with comorbidities or frequent dosing.
## Clinical Pearls
* Terbutaline is significantly more "selective" than older non-selective agents (like epinephrine), but it can still exert beta-1 (cardiac) effects, especially at higher doses.
* In the emergency setting for bronchospasm, inhaled short-acting beta-agonists (SABA) like albuterol are preferred over parenteral terbutaline due to better safety profiles and targeted delivery.
* The FDA issued a "Black Box Warning" significantly limiting the use of terbutaline for preterm labor due to maternal heart and lung complications.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Dosing and protocols may vary based on institutional guidelines, patient history, and local standards of practice. Always verify current prescribing information and drug monographs via official databases (e.g., Lexicomp, UpToDate, or the manufacturer’s package insert) before prescribing or administering medication.
