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# Bricanyl (Terbutaline)
## Overview
Terbutaline sulfate is a selective beta-2 adrenergic agonist. It acts as a bronchodilator by stimulating adenyl cyclase, increasing intracellular cyclic AMP, which leads to bronchial smooth muscle relaxation. It also exerts a tocolytic effect by inhibiting uterine contractions.
## Primary Indications
* **Respiratory:** Relief of bronchospasm in patients with reversible obstructive airway disease (asthma, bronchitis, emphysema).
* **Obstetric (Off-label):** Short-term management of preterm labor (acute tocolysis). *Note: The FDA has warned against the use of injectable terbutaline for the prevention or prolonged treatment (beyond 48–72 hours) of preterm labor due to maternal heart risks.*
## Adult Dosing
* **Bronchospasm (Subcutaneous):** 0.25 mg SC 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.
* **Bronchospasm (Oral):** 2.5 mg to 5 mg every 6 to 8 hours. Maximum 15 mg/day.
* **Tocolysis (Hospital protocol dependent):** Often initiated via continuous IV infusion starting at 2.5–5 mcg/min, titrated upward (typically by 2.5 mcg/min every 20-30 minutes) until contractions cease. Usual infusion rate 10–25 mcg/min. Use lowest effective dose for <48 hours.
## Pediatric Dosing
* **Asthma (Subcutaneous):** 0.01 mg/kg/dose (maximum 0.25 mg). May repeat every 15–20 minutes for two doses; then every 2–6 hours as needed.
* **Asthma (Oral) [12 years and older]:** 2.5 mg to 5 mg every 8 hours. Maximum 15 mg/day.
* **Asthma (Oral) [6–11 years]:** 2.5 mg every 8 hours. Maximum 7.5 mg/day.
## Dose Adjustments
* **Renal Impairment:** Reduce dose in patients with significant renal impairment, as the drug is renally excreted. Specific guidelines vary; monitor closely for toxicity.
## Contraindications
* Hypersensitivity to terbutaline.
* **Tocolysis:** Preterm labor prevention beyond 48–72 hours, or in women with known heart disease.
## Adverse Effects
* **Cardiovascular:** Tachycardia, palpitations, chest pain, arrhythmias, hypertension or hypotension.
* **Metabolic:** Hypokalemia (due to intracellular shift), hyperglycemia.
* **Neurological:** Tremor, nervousness, headache, dizziness.
## Key Drug Interactions
* **Beta-blockers:** May antagonize the effects of terbutaline; avoid concurrent use.
* **Potassium-depleting agents (diuretics, systemic corticosteroids):** May enhance additive hypokalemia.
* **MAO Inhibitors/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Cardiac:** Heart rate (monitor for tachycardia) and ECG if indicated.
* **Electrolytes:** Serum potassium levels, especially in high-dose or prolonged IV use.
* **Respiratory:** Pulmonary function tests or assessment of breath sounds/respiratory effort.
* **Blood Glucose:** Monitor in predisposed patients.
## Clinical Pearls
* Terbutaline is non-catecholamine; it has a longer duration of action than epinephrine.
* When used for asthma, it is generally considered a second-line or rescue option when inhaled beta-agonists are unavailable or inadequate.
* Tolerance develops with chronic use.
* Always verify local institutional protocols for IV tocolytic administration, as concentration and titration speeds vary significantly.
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**Disclaimer:** This information is for educational purposes only. Drug dosing, indications, and safety information are subject to change based on evolving clinical data and institutional policy. Always verify specific patient needs and current prescribing information via official institutional clinical resources or drug monographs (e.g., Lexicomp, Micromedex) before prescribing or administering medication.
