Spasticity

Baclofen exerts its effects as an agonist at presynaptic GABA-B (bicuculline-insensitive) receptors. It acts mainly at the spinal cord level to inhibit the transmission of both monosynaptic and polysynaptic reflexes, possibly by hyperpolarization of primary afferent fiber terminals, resulting in antagonism of the release of putative excitatory transmitters (i.e., glutamic and aspartic acids)

Bioavailability, oral: 100%; Systemic metabolism: Hepatic; 15%; Excretion: Fecal- 10 %, Renal: 69% to 85%; Elimination Half Life: 5 hours

Hypersensitivity

C

Infant risk is minimal.

Common: Cardiovascular: Hypotension (0% to 9% ); Gastrointestinal: Constipation (intrathecal bolus, 0.2%; intrathecal titration, 1.5%; intrathecal maintenance, 5.1% ; oral, 2% to 6% ), Nausea (oral, 4% to 12% ), Vomiting (intrathecal bolus, 6.2%; intrathecal titration, 8.5%; intrathecal maintenance, 4% ); Musculoskeletal: Poor muscle tone (intrathecal bolus, 2.4% to 5.4%; intrathecal titration, 13.5% to 14.4%; intrathecal maintenance, 25.3% to 34.7% ); Neurologic: Asthenia (0.7% to 15% ), Dizziness (intrathecal bolus, 1.7% to 2.4%; intrathecal titration, 1.9% to 2.6%; intrathecal maintenance, 7.9% to 8% ; oral, 5% to 15% ), Headache (intrathecal bolus, 1.6% to 6.6%; intrathecal titration, 2.5% to 7.8%; intrathecal maintenance, 5.1% to 10.7% ; oral, 4% to 8% ), Somnolence (intrathecal bolus, 5.7% to 7.6%; intrathecal titration, 5.9% to 10.5%; intrathecal maintenance, 18.7% to 20.9% ; oral, 10% to 63% ); Renal: Urinary complication (2% to 6% ); Other: Fatigue (2% to 4% ), Shivering (0.5% to 1.3% )

PO 5 mg 3 times a day; may increase dosage by 15 mg/day increments every 3 days to a MAX dose of 80 mg/day (3 to 4 divided doses)

Renal impairment, mild (CrCl 50 to 80 mL/min): Reduce dose by one-third (off-label dosage), Renal impairment, moderate (CrCl 30 to 50 mL/min): Reduce dose by one-half (off-label dosage), Renal impairment, severe (CrCl less than 30 mL/min and not on dialysis): Reduce dose by two-thirds (off-label dosage).