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# Bricanyl (Terbutaline)
## Overview
Terbutaline sulfate is a beta-2 adrenergic agonist. While historically used as a bronchodilator, its clinical utility is now primarily focused on obstetric use for the acute, short-term management of preterm labor (off-label) or as a rescue bronchodilator in asthma. Due to significant cardiovascular risks, its use has declined in favor of more selective agents or alternative therapies.
## Primary Indications
* **Respiratory:** Relief of bronchospasm associated with asthma, bronchitis, and emphysema.
* **Obstetric (Off-label):** Short-term (≤48–72 hours) tocolysis to delay preterm labor.
## Adult Dosing
* **Bronchodilation (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.
* **Bronchodilation (Oral):** 2.5 mg to 5 mg every 6 hours; maximum 15 mg per 24 hours.
* **Tocolysis:** Varies significantly by hospital protocol. Typically initiated as a continuous IV infusion starting at 2.5–5 mcg/min, titrated upward (e.g., by 2.5 mcg/min every 20–30 minutes) until contractions cease or maximum heart rate is reached (usually max 20–25 mcg/min).
* **Note:** FDA has issued a black box warning against the use of terbutaline for prolonged tocolysis (>48–72 hours) due to serious maternal cardiac events.
## Pediatric Dosing
* **Bronchodilation (Subcutaneous):** 0.005–0.01 mg/kg/dose (max 0.25 mg per dose). May repeat every 15–20 minutes for up to 3 doses.
* **Bronchodilation (Oral):** 0.05 mg/kg/dose every 8 hours. Titrate based on response; maximum dose 5 mg/day (usually administered in divided doses).
## Dose Adjustments
* **Renal Impairment:** Exercise caution; reduced clearance may occur. Dose reduction is often required in significant renal failure.
* **Hepatic Impairment:** No specific guidelines; use with caution.
## Contraindications
* Known hypersensitivity to sympathomimetic amines.
* **Obstetric use:** Known ischemic heart disease, cardiac arrhythmias, or conditions where tachycardia or beta-adrenergic stimulation is dangerous (e.g., hyperthyroidism, poorly controlled diabetes).
## Adverse Effects
* **Cardiovascular:** Tachycardia, palpitations, chest pain, hypotension, and rarely, myocardial ischemia or pulmonary edema (especially in pregnancy).
* **Metabolic:** Hypokalemia, hyperglycemia, lactic acidosis.
* **Neurologic/Other:** Tremor, nervousness, headache, dizziness.
## Key Drug Interactions
* **Beta-blockers:** May antagonize effects; avoid concurrent use.
* **Potassium-depleting agents:** (e.g., loop or thiazide diuretics, corticosteroids) may exacerbate terbutaline-induced hypokalemia.
* **MAOIs/TCAs:** May potentiate the pressor effects of beta-agonists.
## Monitoring
* **Respiratory:** Pulmonary function tests, oxygen saturation, and lung sounds.
* **Cardiovascular:** Maternal heart rate, blood pressure, and ECG (if indicated/high dose).
* **Metabolic:** Serum potassium and glucose levels if therapy is prolonged.
* **Obstetric:** Monitor for maternal pulmonary edema (dyspnea, crackles, tachycardia).
## Clinical Pearls
* **Black Box Warning:** Prolonged use (beyond 48–72 hours) in pregnant women is associated with serious maternal cardiac events and death. Do not use for the prevention of preterm labor.
* **Tachyphylaxis:** Tolerance to the bronchodilatory effects may develop with chronic use.
* **Subcutaneous administration:** Ensure injection is into the lateral deltoid; avoiding large blood vessels reduces systemic bolus risk.
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**Disclaimer:** This information is for educational purposes only. Drug information, availability, and clinical protocols can change rapidly. Always verify specific dosing, interactions, and current prescribing information via institutional guidelines or official resources like the FDA package insert or Lexicomp/UpToDate before prescribing or administering medication.
