PharmaceuticalBeta-2 agonistSympathomimeticBronchodilatorTocolytic

Terbutaline

Also known as Bricanyl · Brethine

Written by enwyReviewed 15 Jul 20261 sources0 comments

Terbutaline is a short-acting beta-2 agonist used as a bronchodilator and, off-label, as a tocolytic to slow premature labour. It is occasionally used off-label for fat loss as a clenbuterol alternative, but its short half-life, appreciable beta-1 cross-reactivity and cardiovascular effects limit its appeal. Prolonged tocolytic use has been linked to serious maternal cardiac events, prompting regulatory warnings.

01 Overview

Terbutaline is a selective beta-2 adrenergic agonist available in inhaled, oral, subcutaneous and (historically) intravenous forms. It relaxes bronchial and uterine smooth muscle. Beyond asthma it has been used off-label as a tocolytic to delay preterm labour, though the FDA has warned against prolonged use because of maternal cardiac and metabolic harm.

Among physique users it is sometimes tried as a clenbuterol substitute for its thermogenic and mild anti-catabolic properties. Compared with clenbuterol it is shorter-acting, requiring more frequent dosing, and produces the familiar beta-agonist side effects: tremor, tachycardia, palpitations and metabolic disturbance. There is little human data supporting meaningful fat loss at tolerable doses.

02 Mechanism

Short-acting selective beta-2 adrenergic agonist. Raises cyclic AMP in smooth muscle to produce bronchodilation and uterine relaxation, with a modest thermogenic and lipolytic effect and some beta-1 cardiac stimulation.

03 Dosing

Tier	Dose	Route	Notes
Oral bronchodilator	2.5–5 mg	Oral	2.5-5 mg three times daily as a bronchodilator.
Off-label fat loss	5–15 mg/day	Oral	Off-label physique dosing; sympathomimetic side effects scale with dose.
Inhaled reliever	250–500 mcg	Inhaled	Inhaled rescue dosing.

04 Effects

Effect	Magnitude	Evidence
BronchodilationRelieves bronchospasm, its licensed use.	rapid relief	Clinical
Modest thermogenesisSmall increase in metabolic rate and lipolysis at oral doses; weaker and shorter-acting than clenbuterol.	small	Observational

05 Side effects

Effect	Severity	Frequency	Evidence
Tremor and jitterinessFine tremor and restlessness, dose-dependent and pronounced with oral use.	Mild	Very common orally	Clinical
Tachycardia and palpitationsRaised heart rate and palpitations; prolonged tocolytic use is linked to serious maternal cardiac events.	Moderate	Common	Clinical
Hyperglycaemia and hypokalaemiaBeta-2 stimulation raises blood glucose and shifts potassium intracellularly.	Moderate	With high doses	Clinical

06 Legal status

United States

Prescription drug

FDA-approved bronchodilator; boxed warning against prolonged tocolytic use. WADA restricts systemic beta-2 agonists in sport. · as of Jan 2026

07 References

Terbutaline — clinical pharmacologyStatPearls / NCBI Bookshelf

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.