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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 has tocolytic effects on the uterus.
## Primary Indications
* Relief of bronchospasm associated with asthma, bronchitis, and emphysema.
* *Off-label/Historical:* Tocolysis (prevention of preterm labor)—**Note:** Use for this purpose is discouraged by the FDA due to serious maternal cardiac adverse events and lack of efficacy for long-term suppression.
## Adult Dosing
* **Oral (Bronchodilator):** 2.5 mg to 5 mg every 6 to 8 hours. Maximum: 15 mg/24 hours.
* **Subcutaneous (Bronchospasm):** 0.25 mg injected into the lateral deltoid area. May repeat once after 15–30 minutes if necessary. Do not exceed 0.5 mg within a 4-hour period.
## Pediatric Dosing
* **Oral (Age 12–15 years):** 2.5 mg every 6 hours three times daily. Max: 7.5 mg/24 hours.
* **Subcutaneous (Not recommended for children <12 years):** Safety and efficacy in children <12 years have not been established.
## Dose Adjustments
* **Renal Impairment:** Terbutaline is renally excreted. Use with caution; consider dose reduction in patients with severe renal impairment (CrCl < 30 mL/min).
* **Hepatic Impairment:** No specific guidelines; use caution.
## Contraindications
* Hypersensitivity to terbutaline or any component of the formulation.
* Use as a tocolytic is generally contraindicated for prolonged treatment (>48–72 hours).
## Adverse Effects
* **Common:** Tremor (skeletal muscle), nervousness, tachycardia, palpitations, dizziness, nausea.
* **Serious:** Cardiac arrhythmias, myocardial ischemia, hypokalemia (dose-dependent), hyperglycemia, and pulmonary edema (rare, especially in tocolytic use).
## Key Drug Interactions
* **Beta-blockers:** May antagonize the therapeutic effects of terbutaline and induce severe bronchospasm.
* **Diuretics (Loop/Thiazide):** Increased risk of hypokalemia; monitor K+ levels.
* **MAO Inhibitors/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* Heart rate and blood pressure stabilization.
* Serum potassium levels (if prolonged therapy or high doses are used).
* Blood glucose in diabetic patients.
* Respiratory status/auscultation of lung fields.
## Clinical Pearls
* **Selectivity:** While terbutaline is "beta-2 selective," at higher doses, it loses selectivity and may cause beta-1 mediated cardiac stimulation (tachycardia).
* **Tocolysis Warning:** The FDA has issued a Black Box Warning against the use of oral or long-term (beyond 48–72 hours) injectable terbutaline for preterm labor due to maternal heart and lung complications.
* **Tremor:** Skeletal muscle tremor is a very common dose-limiting side effect; patients should be warned that this is common and often dissipates with continued therapy.
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**Disclaimer:** This information is for educational purposes only. Always verify dosing, contraindications, and drug interactions using current clinical resources (e.g., UpToDate, Lexicomp, or the official manufacturer’s package insert) before prescribing or administering medication.
