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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 bronchial smooth muscle relaxation. It also exerts a tocolytic effect on uterine smooth muscle.
## Primary Indications
* **Respiratory:** Reversible airway obstruction due to asthma, chronic bronchitis, and emphysema.
* **Obstetric (Off-label/Controversial):** Management of preterm labor (acute tocolysis). Note: FDA has issued a boxed warning against prolonged use (>48-72 hours) for preterm labor due to maternal cardiovascular risks.
## Adult Dosing
* **Oral (Bronchodilation):** 2.5–5 mg every 6-8 hours. Maximum: 15 mg/day.
* **Subcutaneous (Bronchodilation):** 0.25 mg injected into the lateral deltoid area. May repeat once after 15–30 minutes. Do not exceed 0.5 mg in a 4-hour period.
* **Tocolysis:** Regimens vary widely by institutional protocol. Typically 2.5–5 mcg/min IV infusion, titrated by 2.5 mcg/min every 20-30 minutes; max 20 mcg/min. Use shortest duration possible.
## Pediatric Dosing
* **Oral (12+ years):** 2.5–5 mg every 8 hours.
* **Oral (Children 6-12 years):** 2.5 mg every 8 hours.
* **Subcutaneous:** 0.005–0.01 mg/kg/dose (max 0.25 mg) every 15-20 minutes for up to 3 doses.
## Dose Adjustments
* **Renal Impairment:** Decrease dose in patients with significant renal impairment; terbutaline is excreted renally.
* **Hepatic Impairment:** No specific guidelines; use with caution.
## Contraindications
* Known hypersensitivity to terbutaline or any component of the formulation.
* **Tocolysis:** Do not use for prevention of preterm labor beyond 48-72 hours or for outpatient maintenance.
## Adverse Effects
* **Common:** Tremor (skeletal muscle), palpitations, tachycardia, nervousness, dizziness, headache.
* **Serious:** Hypokalemia, hyperglycemia, arrhythmias, myocardial ischemia/infarction (specifically with IV tocolysis), pulmonary edema (in pregnancy).
## Key Drug Interactions
* **Beta-blockers:** Antagonize therapeutic effects; may induce bronchospasm.
* **Diuretics (Loop/Thiazide):** May worsen beta-agonist-induced hypokalemia; monitor serum potassium.
* **MAO Inhibitors/TCAs:** Potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Respiratory:** Monitor heart rate, lung sounds, and respiratory effort.
* **Tocolysis:** Continuous maternal EKG (if IV), pulse, BP, and fluid balance (to prevent pulmonary edema). Blood glucose and potassium levels should be monitored if on prolonged IV therapy.
## Clinical Pearls
* Terbutaline is non-selective at high doses and may cause cardiovascular side effects due to beta-1 stimulation.
* Tolerance may develop with regular, long-term use.
* The FDA has specifically warned against the use of injectable or oral terbutaline for the treatment or prevention of preterm labor due to the risk of serious maternal heart problems and death.
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**Educational Disclaimer:** This information is for educational purposes only. Drug dosing, indications, and safety information can change rapidly. Always verify current prescribing information in a reliable database (e.g., Lexicomp, UpToDate, or the official manufacturer’s package insert) before prescribing or administering any medication.
