Can 5mg of Terbutaline Cause Muscle Twitching?
Yes, a 5mg dose of terbutaline can definitely cause muscle twitching and tremor, as this is a well-established, dose-dependent adverse effect of beta-2 adrenergic agonists that occurs through direct stimulation of skeletal muscle beta-2 receptors.
Mechanism and Expected Effects
Skeletal muscle tremor is the most common side effect of beta-2 adrenergic agonists like terbutaline, occurring through direct stimulation of beta-2 receptors in skeletal muscle 1, 2.
The 5mg dose you're asking about is substantially higher than standard therapeutic doses. Guidelines recommend:
Dose-Response Relationship
Tremor intensity increases directly with terbutaline dose 4. Research demonstrates that 2.5mg terbutaline produces measurable tremor, and this effect shows cumulative increases with repeated dosing 4.
At doses exceeding therapeutic levels, terbutaline more than doubles skeletal muscle tremor compared to standard doses 2.
High-dose terbutaline (15mg inhaled) produces systemic concentrations of 23.6 ng/mL and causes measurable increases in muscle contractility 5, confirming significant skeletal muscle effects at suprapharmacologic doses.
Clinical Presentation
The tremor from terbutaline manifests as:
- Fine finger tremor that is most prominent at rest 4
- Increased tremor during light muscle contraction 4
- Paradoxically, tremor may actually decrease during maximal muscle contraction 4
Important Caveats
Route of administration matters critically: Inhaled terbutaline produces equivalent bronchodilation without significant tremor or tachycardia, while systemic administration (IV, subcutaneous, or oral) produces pronounced tremor 2.
If 5mg was given subcutaneously or orally, expect significant tremor. If given by inhalation, tremor would be minimal despite the high dose 2.
Some tolerance develops with repeated dosing: Resting tremor shows habituation after 6 days of continuous use, though tremor during active muscle contraction shows cumulative effects 4.
Distinguishing from Other Causes
Terbutaline-induced tremor is fine, rapid, and bilateral, unlike focal twitching from other neurological causes 4.
Accompanying signs of beta-adrenergic stimulation help confirm the diagnosis: tachycardia (though less prominent than tremor), elevated blood pressure, elevated plasma glucose, and elevated lactate 1, 5.
The tremor should resolve as drug levels decline, with terbutaline having a half-life of approximately 3-6 hours after subcutaneous administration 1.
Management
No specific antidote exists 1. Treatment is supportive with discontinuation of terbutaline 1.
Cardioselective beta-blockers may be considered for severe symptoms, but use extreme caution as they can precipitate bronchospasm 1.
The tremor is generally tolerable and self-limited, resolving as drug levels decline 4.