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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, leading to smooth muscle relaxation in the bronchial tree. It also possesses tocolytic properties by relaxing uterine smooth muscle.
## Primary Indications
* **Respiratory:** Relief of bronchospasm associated with asthma, bronchitis, and emphysema.
* **Obstetric (Off-label/Historical):** Management of preterm labor (note: FDA has issued warnings regarding prolonged use beyond 48-72 hours due to serious maternal cardiac events).
## Adult Dosing
* **Bronchospasm (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 in a 4-hour period.
* **Bronchospasm (Oral):** 2.5 mg to 5 mg every 6 hours, 3 times daily. Maximum: 15 mg/day. (Oral formulation usage has declined significantly in favor of inhaled beta-agonists).
## Pediatric Dosing
* **Bronchospasm (Subcutaneous, 12 years and older):** 0.25 mg.
* **Bronchospasm (Subcutaneous, <12 years):** Not standard; refer to institutional protocols. Generally avoided due to systemic beta-adrenergic side effects.
* **Oral:** Dosage should be titrated based on weight and response. Pediatric oral dosing is rarely utilized due to the availability of safer inhaled alternatives (e.g., albuterol).
## Dose Adjustments
* **Renal Impairment:** Adjust dose in severe impairment; monitor for toxicity due to accumulation of active metabolites.
* **Hepatic Impairment:** No specific guidelines; use with caution.
## Contraindications
* Hypersensitivity to terbutaline or any component.
* **Tocolysis:** Avoid use for preterm labor prevention or treatment for periods exceeding 48–72 hours.
* Cardiac arrhythmias associated with tachycardia.
## Adverse Effects
* **Common:** Tremor (dose-dependent), palpitations, tachycardia, nervousness, dizziness, headache, anxiety.
* **Serious:** Myocardial ischemia, arrhythmias, hypokalemia, hyperglycemia, pulmonary edema (seen in obstetric use).
## Key Drug Interactions
* **Beta-blockers:** May antagonize the bronchodilating effects of terbutaline and induce bronchospasm.
* **Diuretics (Loop/Thiazide):** Non-potassium-sparing diuretics may exacerbate terbutaline-induced hypokalemia.
* **MAO Inhibitors/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Cardiac:** Monitor heart rate and ECG (especially in patients with underlying ischemic heart disease).
* **Electrolytes:** Periodic serum potassium, particularly in high-dose or prolonged settings.
* **Glucose:** Monitor blood glucose in diabetic patients as beta-agonists can induce hyperglycemia.
## Clinical Pearls
* **Systemic vs. Inhaled:** Systemic terbutaline is generally reserved for patients unable to use inhaled beta-agonists or in acute settings where intensive monitoring is available.
* **Tachyphylaxis:** Repeated dosing may lead to tolerance of the bronchodilatory effects.
* **Black Box Warning:** The FDA warns against the use of oral or injectable terbutaline for the prevention or prolonged treatment (beyond 48–72 hours) of preterm labor due to risk of serious maternal heart problems and death.
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**Educational Disclaimer:** This information is for educational purposes only. Terbutaline dosing and safety guidelines can evolve. Always verify current prescribing information and institutional protocols via local clinical pharmacists or updated drug databases (e.g., Lexicomp, UpToDate) before prescribing or administering medication.
