Baclofen Side Effects
Not all side effects for baclofen may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.
For the Consumer
Applies to baclofen: oral tablet
Other dosage forms:
In addition to its needed effects, some unwanted effects may be caused by baclofen. In the event that any of these side effects do occur, they may require medical attention.
If any of the following side effects occur while taking baclofen, check with your doctor or nurse as soon as possible:Less common or rare
- Bloody or dark urine
- chest pain
- hallucinations (seeing or hearing things that are not there)
- mental depression or other mood changes
- ringing or buzzing in the ears
- skin rash or itching
- Blurred or double vision
- convulsions (seizures)
- muscle weakness (severe)
- shortness of breath or unusually slow or troubled breathing
Some of the side effects that can occur with baclofen may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:More common
- dizziness or lightheadedness
- unusual weakness, especially muscle weakness
- Abdominal or stomach pain or discomfort
- clumsiness, unsteadiness, trembling, or other problems with muscle control
- difficult or painful urination or decrease in amount of urine
- false sense of well-being
- frequent urge to urinate or uncontrolled urination
- loss of appetite
- low blood pressure
- muscle or joint pain
- numbness or tingling in hands or feet
- pounding heartbeat
- sexual problems in males
- slurred speech or other speech problems
- stuffy nose
- swelling of ankles
- trouble in sleeping
- unexplained muscle stiffness
- unusual excitement
- unusual tiredness
- weight gain
After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:
- Convulsions (seizures)
- hallucinations (seeing or hearing things that are not there)
- increase in muscle spasm, cramping, or tightness
- mood or mental changes
- unusual nervousness or restlessness
For Healthcare Professionals
Applies to baclofen: compounding powder, intrathecal solution, oral tablet
Nervous system side effects have been common. They have included transient drowsiness and sedation in as many as 63% of treated patients. Dizziness, weakness, and fatigue have been reported commonly. Akathisia, ataxia, opisthotonos, nystagmus, somnolence, dystonia, and decreased reflexes have also been reported. At high doses, coma and respiratory depression may occur. Dystonia, dyskinesia, chorea, encephalopathy, seizures (including generalized nonconvulsive status epilepticus), catatonia, and frontal lobe syndrome have been reported rarely. A case of recurrent transient global amnesia has also been reported.
Most of the side effects listed above were reported following intrathecal injection of baclofen. In addition, patients receiving intrathecal baclofen may be at risk for baclofen toxicity or withdrawal due to pump/catheter malfunction, patient position (facilitating rostral spread) and other factors.
In the first 9 years of postmarketing experience, 27 cases of withdrawal temporally related to the cessation of baclofen therapy were reported. Six of the patients died. In most cases, symptoms of withdrawal appeared within hours to a few days following interruption of baclofen therapy. Common reasons for abrupt interruption of intrathecal baclofen therapy included malfunction of the catheter (especially disconnection), low volume in the pump reservoir, and end of pump battery life. Human error may have also played a causal or contributing role in some cases.
Prevention of abrupt discontinuation of intrathecal baclofen requires careful attention to programming and monitoring of the infusion system, refill scheduling and procedures, and pump alarms. Patients and caregivers should be advised of the importance of keeping scheduled refill visits and should be educated on the early symptoms of baclofen withdrawal.
All patients receiving intrathecal baclofen therapy are potentially at risk for withdrawal. Early symptoms of baclofen withdrawal may include return of baseline spasticity, pruritus, hypotension, and paresthesias. Some clinical characteristics of the advanced intrathecal baclofen withdrawal syndrome may resemble autonomic dysreflexia, infection (sepsis), malignant hyperthermia, neuroleptic-malignant syndrome, or other conditions associated with a hypermetabolic state or widespread rhabdomyolysis.
Rapid, accurate diagnosis and treatment in an emergency room or intensive care setting are important in order to prevent the potentially life-threatening central nervous system and systemic effects of intrathecal baclofen withdrawal.
The suggested treatment for intrathecal baclofen withdrawal is the restoration of intrathecal baclofen at or near the same dosage as before therapy was interrupted. However, if restoration of intrathecal delivery is delayed, treatment with GABA-ergic agonist drugs such as oral or enteral baclofen, or oral, enteral, or intravenous benzodiazepines may prevent potentially fatal sequelae. Oral or enteral baclofen alone should not be relied upon to halt the progression of intrathecal baclofen withdrawal.
Seizures have been reported during overdose and with withdrawal from baclofen intrathecal as well as in patients maintained on therapeutic doses of baclofen intrathecal.
Abrupt withdrawal of intrathecal baclofen (regardless of the cause) has resulted in sequelae that includes high fever, altered mental status, exaggerated rebound spasticity, and muscle rigidity that in rare cases progressed to rhabdomyolysis, multiple organ system failure, and death. Sudden discontinuation of baclofen may result in neuropsychiatric signs and symptoms of withdrawal including confusion, seizures, psychosis, hallucinations, disorientation, dyskinesia, and visual disturbances.
A case has been reported of a febrile reaction to subarachnoid baclofen administration.
Cases of intrathecal mass at the tip of the implanted catheter have been reported, most of them involving pharmacy compounded analgesic admixtures.
One small study has reported, however, that the frequency of depression and anxiety in baclofen-treated patients is not different from patients not taking baclofen.
Psychiatric side effects have been reported including paranoia, mania, euphoria, depression, anxiety, psychosis, hallucinations, paresthesias, hysteria, and personality disorder.
Cardiovascular side effects including hypertension, bradycardia, and orthostatic hypotension have been reported.
Gastrointestinal side effects including nausea, vomiting, constipation, abdominal pain, diarrhea, dysphagia, fecal incontinence, gastrointestinal hemorrhage, and tongue disorder have been reported (especially with rapid dose increases).
Genitourinary side effects including urinary frequency have been reported in 2% to 6% of treated patients. Enuresis, urinary retention, dysuria, abnormal ejaculation, kidney calculus, oliguria, vaginitis and impotence have also been reported.
Endocrine side effects including ovarian cysts have been palpable in 4% of women treated with baclofen for up to one year.
Respiratory side effects including apnea, dyspnea, and hyperventilation have been reported. Cases of acute bronchospasm (particularly in patients with asthma) have been reported rarely.
Hepatic side effects including elevated liver function tests have been reported rarely.
Dermatologic side effects including rash, sweating, alopecia, contact dermatitis, and skin ulcer have been reported.
Hematologic side effects including leukocytosis and petechial rash have been reported.
Other effects including fever, malaise, hypothermia, slurred speech, nightmares, confusion, headache, memory impairment, insomnia, and excitement have been reported.
Oncologic side effects including carcinoma have been reported.
Musculoskeletal side effects including ataxia and muscle pain have been reported.
General side effects have included effects on sleep. One study has reported that a single, therapeutic dose of baclofen alters sleep architecture and produces a small reduction in mean sleep oxygen saturation, but does not significantly increase sleep disordered breathing.
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