BACLOFEN

Baclofen USP, is a muscle relaxant and antispastic, available as 10 mg and 20 mg tablets for oral administration. Its chemical name is 4-amino-3-(4-chlorophenyl)- butanoic acid, and its structural formula is Baclofen USP is a white to off-white crystalline powder, with a molecular weight of 213.66. It is slightly soluble in water, very slightly soluble in methanol and in 96% ethanol, practically insoluble in acetone, insoluble in chloroform, dissolves in dilute mineral acids and in dilute solutions of alkali hydroxides. Inactive Ingredients. Colloidal silicon dioxide, magnesium stearate, microcrystalline cellulose and pregelatinized starch (maize). FDA approved dissolution test specifications differ from USP. Chemical Structure

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 tablets treatment will aid in restoring residual function. Baclofen tablets may also be of some value in patients with spinal cord injuries and other spinal cord diseases. Baclofen tablets are 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.

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 If benefits are not evident after a reasonable trial period, patients should be slowly withdrawn from the drug (see WARNINGS Abrupt Drug Withdrawal ).

Hypersensitivity to baclofen.

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: Neuropsychiatric: Confusion (1% to 11%), headache (4% to 8%), insomnia (2% to 7%); and, rarely, euphoria, excitement, depression, hallucinations, paresthesia, muscle pain, tinnitus, slurred speech, coordination disorder, tremor, rigidity, dystonia, ataxia, blurred vision, nystagmus, strabismus, miosis, mydriasis, diplopia, dysarthria, epileptic seizure. Cardiovascular: Hypotension (0% to 9%). Rare instances of dyspnea, palpitation, chest pain, syncope. Gastrointestinal: Nausea (4% to 12%), constipation (2% to 6%); and, rarely, dry mouth, anorexia, taste disorder, abdominal pain, vomiting, diarrhea, and positive test for occult blood in stool. Genitourinary: Urinary frequency (2% to 6%); and, rarely, enuresis, urinary retention, dysuria, impotence, inability to ejaculate, nocturia, hematuria. Other: Instances of rash, pruritus, ankle edema, excessive perspiration, weight gain, nasal congestion. Some of the CNS and genitourinary symptoms may be related to the underlying disease rather than to drug therapy. The following laboratory tests have been found to be abnormal in a few patients receiving baclofen: increased SGOT, elevated alkaline phosphatase, and elevation of blood sugar.