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# Bricanyl (Terbutaline)
## Overview
Terbutaline is a selective beta-2 adrenergic agonist. It acts as a bronchodilator by stimulating adenyl cyclase to increase cyclic AMP levels, causing bronchial smooth muscle relaxation. It also possesses tocolytic properties, though this use is largely discouraged by regulatory agencies due to maternal safety risks.
## Primary Indications
* **Respiratory:** Relief of bronchospasm associated with asthma, bronchitis, and emphysema.
* **Obstetric (Off-label/Historical):** Acute tocolysis for preterm labor (use is strictly limited/avoided per FDA mandates).
## Adult Dosing
* **Subcutaneous:** 0.25 mg injected into the lateral deltoid area. May repeat once after 15–30 minutes if necessary. Do not exceed 0.5 mg within a 4-hour period.
* **Oral:** 2.5 to 5 mg every 6 to 8 hours. Maximum 15 mg/24 hours.
## Pediatric Dosing
* **Subcutaneous (Children >12 years):** 0.25 mg as a single dose; may repeat once if needed.
* **Subcutaneous (Children 12 years and younger):** Dose is generally avoided, but established literature suggests 0.005–0.01 mg/kg/dose (max 0.25 mg).
* **Oral (Children 12–15 years):** 2.5 mg every 8 hours. Max 7.5 mg/24 hours.
## Dose Adjustments
* **Renal Impairment:** Reduce dose in patients with impaired renal function, as terbutaline is primarily excreted renally.
* **Hepatic Impairment:** No specific guidelines; caution advised.
## Contraindications
* Known hypersensitivity to sympathomimetic amines.
* Use as a long-term oral tocolytic agent (Black Box Warning for maternal pulmonary edema, myocardial ischemia, and death).
* Cardiac arrhythmias associated with tachycardia.
## Adverse Effects
* **Common:** Tachycardia, palpitations, tremor (skeletal muscle), nervousness, and headache.
* **Serious:** Hypokalemia (with high dose/frequent use), hyperglycemia, myocardial ischemia, pulmonary edema, and cardiac arrhythmias.
## Key Drug Interactions
* **Beta-blockers:** Antagonize the effect of terbutaline and may induce severe bronchospasm.
* **Diuretics (Loop/Thiazide):** Potential for terbutaline-induced hypokalemia is additive.
* **MAO Inhibitors / TCAs:** Potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **HR and ECG:** Monitor for tachycardia or arrhythmia (especially in pregnant patients or those with existing cardiac history).
* **Electrolytes:** Periodic serum potassium, particularly during frequent dosing.
* **Glucose:** Monitor in diabetic patients due to potential transient hyperglycemia.
## Clinical Pearls
* **Beta-2 Selectivity:** While considered "selective," it loses selectivity at higher doses, leading to increased beta-1 (cardiac) stimulation.
* **Tolerance:** Prolonged use of oral terbutaline can result in tolerance; it should not be the primary agent for chronic asthma management.
* **Tocolysis Note:** If used for acute tocolysis (rare/local protocol dependent), monitor maternal heart rate and breath sounds closely; hold dose if HR >120 bpm.
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**Disclaimer:** This information is for educational purposes only. Clinical practices vary by institution. Always consult your local formulary, institutional protocols, and current FDA-approved labeling or a board-certified pharmacist before prescribing or administering medication.
