Baclofen Does Not Typically Increase Heart Rate During Therapeutic Use
Baclofen itself does not cause tachycardia as a direct therapeutic effect; however, tachycardia is a prominent feature of baclofen withdrawal syndrome, which occurs with abrupt discontinuation of chronic baclofen therapy 1.
Direct Effects of Baclofen on Heart Rate
The FDA-approved drug label for baclofen does not list tachycardia as an adverse effect of the medication itself 2. The most common adverse reactions include drowsiness (10-63%), dizziness (5-15%), weakness (5-15%), and hypotension (0-9%), with rare cardiovascular effects including hypotension, dyspnea, palpitation, chest pain, and syncope 2.
Baclofen Withdrawal: The Critical Caveat
The most important clinical consideration is that tachycardia is a hallmark symptom of baclofen withdrawal syndrome, not of baclofen administration. Abrupt discontinuation of baclofen—particularly intrathecal baclofen—can produce severe withdrawal symptoms including:
- Visual and auditory hallucinations
- Anxiety and agitation
- Delirium and fever
- Tremors
- Tachycardia
- Seizures 1
Intrathecal baclofen withdrawal is potentially life-threatening, with symptoms including high fever, altered mental status, rebound spasticity, and muscle rigidity that can progress to rhabdomyolysis, multiorgan failure, and death 1. Cardiac arrest has been reported as a rare complication of intrathecal baclofen withdrawal 3.
Experimental and Toxic Dose Effects
Research evidence reveals a more complex picture at non-therapeutic doses:
- Toxic doses (85 mg/kg in animal studies) significantly increased heart rate and blood pressure 4
- High experimental doses in animal models produced marked increases in blood pressure accompanied by rises in heart rate through central sympathetic mechanisms 5, 6
- Baclofen overdose in humans can cause hemodynamic volatility with alternating hypotension and hypertension 7
These effects are mediated centrally through the sympathetic nervous system and are abolished by sympathetic blockade 5, 6.
Clinical Management Recommendations
Continue baclofen throughout the perioperative period, including on the day of surgery 1. This guideline specifically addresses the risk of withdrawal symptoms, including tachycardia.
If baclofen discontinuation is necessary after long-term use:
- Taper slowly over an extended period
- Never abruptly discontinue, especially intrathecal baclofen
- Monitor for withdrawal symptoms including tachycardia, fever, agitation, and altered mental status
- Have specialist input for patients on intrathecal baclofen 1
Bottom Line
At therapeutic doses, baclofen does not increase heart rate and may actually cause hypotension. Tachycardia associated with baclofen is almost exclusively a withdrawal phenomenon that occurs when the medication is abruptly stopped after chronic use, not a direct effect of the drug itself. This distinction is critical for safe clinical management.