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# Bricanyl (Terbutaline)
## Overview
Terbutaline is a selective $\beta_2$-adrenergic agonist that functions as a bronchodilator. It relaxes bronchial smooth muscle and inhibits the release of endogenous spasmogens. While historically used as a tocolytic for preterm labor, this use is no longer recommended by the FDA due to serious maternal cardiac risks and mortality.
## Primary Indications
* Relief of bronchospasm associated with asthma, chronic bronchitis, and emphysema.
## Adult Dosing
* **Oral:** 2.5 mg to 5 mg every 6 to 8 hours. Do not exceed 15 mg in 24 hours.
* **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.
## Pediatric Dosing
* **Oral (12–15 years):** 2.5 mg every 8 hours. Do not exceed 7.5 mg in 24 hours.
* **Oral (<12 years):** Not generally recommended due to lack of established safety/efficacy data; clinical practice varies by institution.
* **Subcutaneous:** Not typically recommended for pediatric use.
## Dose Adjustments
* **Renal Impairment:** Reduce dose by 50% in patients with significant renal impairment (CrCl < 50 mL/min).
* **Hepatic Impairment:** No specific guidelines; use with caution.
## Contraindications
* Hypersensitivity to terbutaline or any component of the formulation.
* Prolonged tocolysis (use > 48–72 hours) for preterm labor is contraindicated (Black Box Warning).
## Adverse Effects
* **Common:** Tremor, nervousness, palpitations, tachycardia, dizziness, headache.
* **Serious:** Hypokalemia, hyperglycemia, cardiac arrhythmias, myocardial ischemia, pulmonary edema (linked to prolonged IV use in obstetrics).
## Key Drug Interactions
* **Beta-blockers:** May antagonize the effects of terbutaline; avoid non-selective beta-blockers.
* **Diuretics:** Non-potassium sparing diuretics (e.g., loop or thiazides) may potentiate terbutaline-induced hypokalemia.
* **MAO Inhibitors/Tricyclics:** May potentiate the pressor effects of terbutaline on the vascular system.
## Monitoring
* **Cardiac:** Pulse rate, blood pressure, and ECG (if history of arrhythmias).
* **Metabolic:** Serum potassium (especially if on diuretics) and blood glucose levels in diabetic patients.
* **Respiratory:** Monitor pulmonary function/symptom relief.
## Clinical Pearls
* **Toxicity:** Overdose may present as severe tachycardia, hypotension, and tremor. Manage with cardioselective beta-blockers (e.g., metoprolol) cautiously, as they may induce bronchospasm.
* **Tolerance:** Prolonged use can lead to tachyphylaxis (diminished effect over time).
* **Inhalation:** While terbutaline is available as an injectable and oral, inhaled short-acting beta-agonists (e.g., albuterol) are preferred for asthma due to fewer systemic side effects.
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**Disclaimer:** This information is for educational purposes only. Drug dosing, indications, and safety profiles are subject to change. Always verify current prescribing information in a local formulary or clinical database (e.g., Lexicomp, UpToDate) before prescribing or administering medication.
