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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 and obstetric indications (preterm labor), its use for obstetric inhibition of labor is now strongly discouraged due to significant maternal cardiovascular safety concerns.
## Primary Indications
* Reversible airway obstruction associated with asthma, bronchitis, and emphysema.
* *Note:* Use for preterm labor is no longer recommended by the FDA due to potential for serious maternal heart problems and death.
## Adult Dosing
* **Subcutaneous (Injection):** 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:** Historically 2.5–5 mg every 8 hours. Oral use is largely obsolete in clinical practice.
## Pediatric Dosing
* **Ages 12 years and older:** Follow adult subcutaneous dosing.
* **Ages younger than 12 years:** Safety and efficacy have not been well-established. Use is clinical judgment-based; consult local institutional pediatric protocols.
## Dose Adjustments
* **Renal Impairment:** Reduce dose in patients with significant renal impairment; monitor for toxicity due to accumulation.
* **Hepatic Impairment:** No formal adjustment guidelines; observe for systemic effects.
## Contraindications
* Known hypersensitivity to terbutaline.
* Prophylactic use for preterm labor (Boxed Warning).
## Adverse Effects
* **Common:** Nervousness, tremor, palpitations, tachycardia, dizziness, headache.
* **Serious:** Paradoxical bronchospasm, cardiac arrhythmias (atrial fibrillation, premature ventricular contractions), myocardial ischemia, hypokalemia, hyperglycemia.
## Key Drug Interactions
* **Beta-blockers:** May antagonize the effects of terbutaline and induce bronchospasm.
* **Diuretics (loop/thiazide):** Concurrent use may potentiate ECG changes or hypokalemia induced by $\beta_2$-agonists.
* **MAOIs/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Cardiovascular:** Heart rate, rhythm, and blood pressure.
* **Metabolic:** Serum potassium levels (monitor for hypokalemia, especially in nebulized or high-dose scenarios) and blood glucose.
* **Respiratory:** Clinical response, oxygen saturation, and lung auscultation.
## Clinical Pearls
* **Systemic Side Effects:** Terbutaline has higher affinity for systemic absorption compared to inhaled short-acting $\beta_2$-agonists (e.g., albuterol).
* **Tachyphylaxis:** Chronic use may lead to a diminished response to the drug.
* **Emergency Setting:** Its role is increasingly limited as inhaled albuterol is preferred for asthma due to a wider therapeutic index and localized action.
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**Educational Disclaimer:** This information is for educational purposes and does not substitute for professional clinical judgment. Always verify current prescribing information, institutional protocols, and patient-specific contraindications via reliable drug databases (e.g., Lexicomp, Micromedex) or the manufacturer's package insert before prescribing or administering medication.
