Baclofen – Side Effects

Description

Baclofen is a gamma-aminobutyric acid (GABA) agonist used as a skeletal muscle relaxant. Although originally designed in 1962 to treat epilepsy, baclofen was not effective in treating this condition but instead was shown to reduce spasticity in selected patients. It was reintroduced in 1971 as a treatment for spasticity and was later approved by the FDA in 1977. Baclofen is used to manage severe muscle spasms of cerebral or spinal cord origins, including multiple sclerosis and traumatic brain injury.

Baclofen was investigated for use in alcohol dependence and withdrawal; however, evidence is limited and there is inconsistent evidence to suggest its clinical efficacy in managing alcohol dependence or withdrawal symptoms.

Brand names

Fleqsuvy, Gablofen, Kemstro, Lioresal, Lyvispah, Ozobax

Storage

• Store baclofen at room temperature. Keep it between 68°F and 77°F (20°C and 25°C).
• Don’t store this medication in moist or damp areas, such as bathrooms.

Identity of Baclofen

Type of medicine	Skeletal Muscle Relaxants
Synonyms	Baclofen, Baclofène, Baclofeno, Baclofenum, DL-Baclofen
Molecular Formula	C10H12ClNO2
Molecular Weight	213.661g/mol
IUPAC Names	4-amino-3-(4-chlorophenyl)butanoic acid
Structural formula of main components
Pure active ingredient	Baclofen
Appearance	White to off-white crystalline powder
Melting point	372 to 376 °F
Solubility	less than 1 mg/mL at 64 °F
Excretion	Renal excretion
Available as	Oral tablet, oral suspensions, and injectables
Prescription	Prescription Required

What do people use baclofen for?

Baclofen has various effects on the body that make it suitable for the treatment of several conditions. It works by:

• Alleviating muscle tightness and stiffness
• Reducing the severity and frequency of muscle spasms
• Improving muscle movement
• Alleviating pain

Doctors may prescribe baclofen to help treat the following conditions:

• Multiple sclerosis (MS)
• Motor neuron disease (MND)
• Cerebral palsy
• Meningitis

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

• Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
• CNS depression—slow or shallow breathing, shortness of breath, feeling faint, dizziness, confusion, trouble staying awake

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

• Dizziness
• Drowsiness
• Headache
• Muscle weakness
• Nausea

This list may not describe all possible side effects. Call your doctor for medical advice about side effects.

Mechanism of action

The exact mechanism of action of baclofen is unclear. It is an agonist at the beta subunit of gamma-aminobutyric acid (GABA) receptors expressed on pre- and post-synaptic neurons. Upon binding to GABAB receptors, baclofen causes an influx of potassium into the neuron, leading to hyperpolarization of the neuronal membrane and decreased calcium influx at presynaptic nerve terminals. This results in a decreased rate of action potential threshold being reached by presynaptic neurons and reduced action potential of postsynaptic motor neurons that innervate the muscle spindles. Baclofen thereby inhibits the transmission of both mono- and polysynaptic reflexes at the spinal cord, relaxing spasticity. Baclofen may act on some voltage-gated calcium channels; however, the clinical significance of this is unclear.

Baclofen and other drugs

Baclofen can interact with other drugs, and this may increase the risk of side effects.

Medications that may interact with it include:

• Other muscle relaxant medications
• Nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen
• Medications to treat high blood pressure
• The mood stabilizer lithium
• The antidepressant medication amitriptyline
• The Parkinson’s disease medication levodopa

People should also notify the doctor if they are taking any dietary or herbal supplements, as some of these products may interact with medications such as baclofen.

How to take baclofen?

This dosage information is for baclofen oral tablet. All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

• Your age
• The condition being treated
• How severe your condition is
• Other medical conditions you have
• How you react to the first dose

Forms and strengths

Generic: Baclofen

• Form: oral tablet
• Strengths: 10 milligrams (mg), 20 mg

Dosage for muscle spasms

Adult dosage (ages 18 years and older)

• Typical starting dosage. You should start taking this drug on the following schedule:
  • Days 1 through 3: Take 5 mg three times per day.
  • Days 4 through 6: Take 10 mg three times per day.
  • Days 7 through9: Take 15 mg three times per day.
  • Days 10 through 12: Take 20 mg three times per day.
• Dosage increases. Your doctor will slowly increase your dosage every three days. Your doctor may further increase your dosage if needed.
• Maximum dosage. A total of 80 mg per day taken in four divided doses of 20 mg each.

Child dosage (ages 12 to 17 years)

• Typical starting dosage. You should start taking this drug on the following schedule:
  • Days 1 through 3: Take 5 mg three times per day.
  • Days 4 through 6: Take 10 mg three times per day.
  • Days 7 through 9: Take 15 mg three times per day.
  • Days 10 through 12: Take 20 mg three times per day.
• Dosage increases. Your doctor will slowly increase your dosage every three days. Your doctor may further increase your dosage if needed.
• Maximum dosage. A total of 80 mg per day taken in four divided doses of 20 mg each.

Child dosage (ages 0 to 11 years)

This medication hasn’t been studied in children. It shouldn’t be used in people younger than 12 years.

In case of emergency/overdose

In case of overdose, call the nearby poison control helpline. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services.

Symptoms of overdose may include:

• Vomiting
• Weak muscle tone
• Drowsiness
• Vision problems
• Coma
• Difficulty breathing
• Seizures

Warnings

• Abrupt Drug Withdrawal: Hallucinations and seizures have occurred on abrupt withdrawal of baclofen. Therefore, except for serious adverse reactions, the dose should be reduced slowly when the drug is discontinued.
• Impaired Renal Function: Because baclofen is primarily excreted unchanged through the kidneys, it should be given with caution, and it may be necessary to reduce the dosage.
• Stroke: Baclofen has not significantly benefited patients with stroke. These patients have also shown poor tolerability to the drug.

Pregnancy, breastfeeding and fertility while taking baclofen

Balofen and pregnancy

Baclofen is not often recommended in pregnancy. However, if you need baclofen to stay well, your doctor may recommend that you keep taking it.

Talk to your doctor about the benefits and possible risks of taking baclofen in pregnancy. If you take it in later pregnancy your baby may need to be monitored for withdrawal symptoms.

If you become pregnant while taking it then contact your doctor. They may recommend reducing your dose or gradually stopping the medicine.

Baclofen and breastfeeding

If your doctor or health visitor says your baby is healthy, you can take baclofen while you’re breastfeeding. It’s important to keep taking baclofen to keep you well.

There is not much information about taking baclofen while breastfeeding, but information shows that it passes into breast milk in small amounts. It has not been known to cause any side effects in breastfed babies.

Contact your health visitor, midwife, pharmacist or doctor as soon as possible if your baby:

• Is not feeding as well as usual or seems to have a dry mouth
• Seems unusually sleepy
• Is sweaty or develops a rash
• Is being sick or has diarrhoea
• Is causing you any other concerns

Baclofen and fertility

There’s no evidence to suggest that taking baclofen will reduce fertility in either men or women.

But speak to a pharmacist or your doctor if you’re trying to get pregnant.