Baclofen is a medication used to treat spasticity. It is used as a central nervous system depressant and skeletal muscle relaxant. It is also used in topical creams to help with pain. Chemically it is a derivative of the neurotransmitter γ-aminobutyric acid (GABA). It is believed to work by activating (or agonizing) GABA receptors, specifically the GABAB receptors. Its beneficial effects in spasticity result from its actions in the brain and spinal cord
Baclofen, USP is a muscle relaxant and antispastic.
Its chemical name is 4-amino-3-(4-chlorophenyl)-butanoic acid. The structural formula is:
Baclofen, USP is a white to off-white odorless or practically odorless crystalline powder. It is slightly soluble in water, very slightly soluble in methanol and insoluble in chloroform.
Each tablet, for oral administration, contains 10 mg or 20 mg Baclofen, USP. In addition, each tablet contains the following inactive ingredients: anhydrous lactose, colloidal silicon dioxide, dibasic calcium phosphate dihydrate, magnesium stearate, microcrystalline cellulose and sodium starch glycolate.
Baclofen – Clinical Pharmacology
The precise mechanism of action of Baclofen is not fully known. Baclofen is capable of inhibiting both monosynaptic and polysynaptic reflexes at the spinal level, possibly by hyperpolarization of afferent terminals, although actions at supraspinal sites may also occur and contribute to its clinical effect. Although Baclofen is an analog of the putative inhibitory neurotransmitter gamma-aminobutyric acid (GABA), there is no conclusive evidence that actions on GABA systems are involved in the production of its clinical effects. In studies with animals Baclofen has been shown to have general CNS depressant properties as indicated by the production of sedation with tolerance, somnolence, ataxia, and respiratory and cardiovascular depression. Baclofen is rapidly and extensively absorbed and eliminated. Absorption may be dose-dependent, being reduced with increasing doses. Baclofen is excreted primarily by the kidney in unchanged form and there is relatively large intersubject variation in absorption and/or elimination.
Baclofen is a muscle relaxer and an antispastic agent.
Baclofen is used to treat muscle symptoms caused by multiple sclerosis, including spasm, pain, and stiffness.
Baclofen is sometimes used to treat muscle spasms and other symptoms in people with injury or disease of the spinal cord.
- Cerebral Spasticity
- Spinal Spasticity
- Cerebral Spasticity
- Spinal Spasticity
Baclofen tablets are not indicated in the treatment of skeletal muscle spasm resulting from rheumatic disorders.The efficacy of baclofen tablets in stroke, cerebral palsy, and Parkinson’s disease has not been established and, therefore, it is not recommended for these conditions.
Do not use baclofen at a time when you need muscle tone for safe balance and movement during certain activities.
Do not stop using baclofen suddenly, or you could have unpleasant withdrawal symptoms.
Before taking this medicine
You should not use baclofen if you are allergic to it.
To make sure this medicine is safe for you, tell your doctor if you have:
- kidney disease;
- epilepsy or other seizure disorder;
- a history of stroke or blood clots; or
- if you also use a narcotic (opioid) medication.
Using baclofen during pregnancy could harm the unborn baby. In animal studies, it caused low birth weight and birth defects. However, it is not known whether these effects would occur in humans.
It is not known whether baclofen passes into breast milk or if it could harm a nursing baby. You should not breast-feed while you are using this medicine.
Using baclofen may increase your risk of developing an ovarian cyst. Talk with your doctor about your specific risk.
Baclofen is not approved for use by anyone younger than 12 years old.
How should I take baclofen?
Take baclofen exactly as prescribed by your doctor. Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use this medicine in larger or smaller amounts or for longer than recommended.
Call your doctor if your muscle symptoms do not improve, or if they get worse.
Do not stop using this medicine suddenly, or you could have unpleasant withdrawal symptoms such as hallucinations or a seizure. Ask your doctor how to safely stop using this medicine.
Store at room temperature away from moisture and heat.
Doses of Baclofen
Applies to the following strength(s): 10 mg ; 20 mg ; 0.05 mg/mL ; 0.5 mg/mL ; 1 mg/mL ; 2 mg/mL ; 5 mg/mL
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Overdose symptoms may include muscle weakness, vomiting, drowsiness, dilated or pinpoint pupils, weak or shallow breathing, seizure, or coma.
What should I avoid while taking baclofen?
Do not use baclofen at a time when you need muscle tone for safe balance and movement during certain activities. In some situations, it may be dangerous for you to have reduced muscle tone.
Drinking alcohol with this medicine can cause side effects.
This medication may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
Baclofen side effects
Get emergency medical help if you have signs of an allergic reaction to baclofen: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
- weak or shallow breathing;
- confusion, hallucinations; or
- a seizure (convulsions).
Common baclofen side effects may include:
- drowsiness, dizziness, weakness, tired feeling;
- sleep problems (insomnia);
- nausea, constipation; or
- urinating more often than usual.
What other drugs will affect baclofen?
Taking baclofen with other drugs that make you sleepy or slow your breathing can cause dangerous side effects or death. Ask your doctor before taking a sleeping pill, narcotic pain medicine, prescription cough medicine, a muscle relaxer, or medicine for anxiety, depression, or seizures.
Other drugs may interact with baclofen, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using
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
Symptoms of overdose:
- Blurred or double vision
- convulsions (seizures)
- muscle weakness (severe)
- shortness of breath or unusually slow or troubled breathing
Minor Side Effects
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:
- dizziness or lightheadedness
- unusual weakness, especially muscle weakness
Less common or rare
- Abdominal or stomach pain or discomfort
- clumsiness, unsteadiness, trembling, or other problems with muscle control
- difficult or painful urination or a decrease in the amount of urine
- false sense of well-being
- frequent urge to urinate or uncontrolled urination
- a headache
- 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
Side Effects: Post Treatment
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 suspension, oral tablet
Common (1% to 10%): Cardiac output decreased, hypotension, hypertension, diminished cardiovascular functions, peripheral edema
Rare (less than 0.1%): Arrhythmias, palpitations, chest pain
Frequency not reported: Bradycardia, orthostatic hypotension
Common (1% to 10%): Rash, hyperhidrosis, urticaria/pruritus, facial edema
Uncommon (0.1% to 1%): Alopecia, diaphoresis
Frequency not reported: Rash, sweating, contact dermatitis, skin ulcer
Common (1% to 10%): Ovarian cysts are palpable in 4% of women treated with for up to one year.
Very common (10% or more): Nausea (especially at start of therapy) (up to 11%)
Common (1% to 10%): Dry mouth, GI disorder/disturbance, constipation, diarrhea, retching, vomiting, increased salivation
Uncommon (0.1% to 1%): Dysphagia, dehydration, ileus, decreased taste sensation
Rare (less than 0.1%): Colicky abdominal pain, anorexia
Frequency not reported: GI hemorrhage
Very common (10% or more): Urinary retention (up to 12%)
Common (1% to 10%): Urinary incontinence, urination impaired, sexual dysfunction, urinary frequency, enuresis, dysuria
Rare (less than 0.1%): Erectile dysfunction
Frequency not reported: Dysuria, abnormal ejaculation, oliguria, vaginitis
Frequency not reported: Leukocytosis, petechial rash
Rare (less than 0.1%): Disorders of hepatic function (e.g., increased AST)
Common (1% to 10%): Pneumonia
Uncommon (0.1% to 1%): Septicemia
Common (1% to 10%): Decreased appetite
Frequency not reported: Blood glucose increased
Very common (10% or more): Hypotonia (up to 52%), lower extremity weakness (up to 15%), disturbances of gait and balance
Common (1% to 10%): Muscular weakness, myalgia, upper extremity weakness, back pain, muscular hypertonia
Very common (10% or more): Somnolence (up to 28%), drowsiness (up to 18%), headache (up to 16%), seizures (especially on discontinuation of therapy) (up to 15%), sedation, dizziness (up to 12%)
Common (1% to 10%): Fatigue, ataxia, tremor, lightheadedness, lassitude, exhaustion, numbness/itching/tingling, slurred speech, lethargy, hypertonia, paresthesia
Rare (less than 0.1%): Dysarthria, dysgeusia, syncope, dyskinesia, coma, potentially life-threatening withdrawal symptoms (as a result of sudden interruption of drug delivery)
Common (1% to 10%): Tinnitus, pain, asthenia
Uncommon (0.1% to 1%): Accidental injury, weight loss
Very rare (less than 0.01%): Hypothermia
Frequency not reported: Drug withdrawal syndrome
Uncommon (0.1% to 1%): Subdural hemorrhage, accidental injury, weight loss
Common (1% to 10%): Nystagmus, visual impairment, accommodation disorder, blurred vision, double vision, amblyopia
Common (1% to 10%): Confusional state, hallucination, depression, insomnia, euphoric mood, nightmare, personality changes
Uncommon (0.1% to 1%): Memory loss/impairment, suicidal ideation, attempted suicide
Rare (less than 0.1%): Excitement
Very rare (less than 0.01%): Kidney calculus
Common (1% to 10%): Respiratory depression, hypoventilation, dyspnea, bradypnea, feeling of pressure in the chest…