BACLOFEN TABLETS, USP

Muscle Relaxant Antispastic

Rev. 6-02
15133-02

Baclofen USP is a muscle relaxant and antispastic. Its chemical name is 4-amino-3-(4-chlorophenyl)-butanoic acid. Its molecular formula is C₁₀H₁₂CINO₂ and its structural formula is:

Baclofen USP is a white to off-white, odorless or practically odorless crystalline powder, with a molecular weight of 213.66. It is slightly soluble in water, very slightly soluble in methanol and insoluble in chloroform.

Each tablet, for oral administration, contains 10 or 20 mg of baclofen. In addition, each tablet contains the following inactive ingredients: Crospovidone, anhydrous lactose, magnesium stearate and povidone.

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 tablets are useful for the alleviation of signs and symptoms of spasticity resulting from multiple sclerosis, particularly for the relief of flexor spasms and concomitant pain, clonus, and muscular rigidity.

Patients should have reversible spasticity so that baclofen treatment will aid in restoring residual function.

Baclofen may also be of some value in patients with spinal cord injuries and other spinal cord diseases.

Baclofen is not indicated in the treatment of skeletal muscle spasm resulting from rheumatic disorders.

The efficacy of baclofen in stroke, cerebral palsy, and Parkinson's disease has not been established and, therefore, it is not recommended for these conditions.

Baclofen tablets are contraindicated in patients with a hypersensitivity to baclofen.

Safe use of baclofen in pediatric patients under age 12 has not been established, and it is, therefore, not recommended for use in pediatric patients.

Because of the possibility of sedation, patients should be cautioned regarding the operation of automobiles or other dangerous machinery, and activities made hazardous by decreased alertness. Patients should also be cautioned that the central nervous system effects of baclofen may be additive to those of alcohol and other CNS depressants.

Baclofen should be used with caution where spasticity is utilized to sustain upright posture and balance in locomotion or whenever spasticity is utilized to obtain increased function.

In patients with epilepsy, the clinical state and electroencephalogram should be monitored at regular intervals, since deterioration in seizure control and EEG have been reported occasionally in patients taking baclofen. It is not known whether this drug is excreted in human milk. As a general rule, nursing should not be undertaken while a patient is on a drug since many drugs are excreted in human milk.

A dose-related increase in incidence of ovarian cysts and a less marked increase in enlarged and/or hemorrhagic adrenal glands was observed in female rats treated chronically with baclofen.

Ovarian cysts have been found by palpation in about 4% of the multiple sclerosis patients that were treated with baclofen for up to one year. In most cases these cysts disappeared spontaneously while patients continued to receive the drug. Ovarian cysts are estimated to occur spontaneously in approximately 1% to 5% of the normal female population.

The most common is transient drowsiness (10 to 63%). In one controlled study of 175 patients, transient drowsiness was observed in 63% of those receiving baclofen compared to 36% of those in the placebo group. Other common adverse reactions are dizziness (5 to 15%), weakness (5 to 15%) and fatigue (2 to 4%). Others reported:

Signs and Symptoms: Vomiting, muscular hypotonia, drowsiness, accommodation disorders, coma, respiratory depression, and seizures.

Treatment: In the alert patient, empty the stomach promptly by induced emesis followed by lavage. In the obtunded patient, secure the airway with a cuffed endotracheal tube before beginning lavage (do not induce emesis). Maintain adequate respiratory exchange, do not use a respiratory stimulants.

The determination of optimal dosage requires individual titration. Start therapy at a low dosage and increase gradually until optimum effect is achieved (usually between 40 to 80 mg daily).

The following dosage titration schedule is suggested:

•  5 mg t.i.d. for 3 days
•  10 mg t.i.d. for 3 days
•  15 mg t.i.d. for 3 days
•  20 mg t.i.d. for 3 days

Thereafter additional increases may be necessary but the total daily dose should not exceed a maximum of 80 mg daily (20 mg q.i.d.).

The lowest dose compatible with an optimal response is recommended. If benefits are not evident after a reasonable trial period, patients should be slowly withdrawn from the drug (see WARNINGS Abrupt Drug Withdrawal).

Baclofen tablets, USP for oral use, are supplied in the following forms:

As 10 mg – Compressed tablet, white, 5/16” diameter, round; one side scored and debossed BAC and 10, one side debossed 832, in bottles of 100, 500 and 1000.

As 20 mg – Compressed tablet, white, 13/32” diameter, round; one side scored and debossed 832 and BC20, one side plain, bottles of 100, 500 and 1000.

Dispense in a tight container as defined in the USP.

Keep this and all drugs out of the reach of children.

Store at controlled room temperature 15° - 30°C (59° - 86°F).

Rx only
Rev. 06-02
15133-02

Manufactured by
UPSHER-SMITH LABORATORIES, INC.
Minneapolis, MN 55447