Pharmacology: Pharmacokinetics: Baclofen is rapidly and almost completely absorbed from the gastrointestinal tract following an oral dose. Peak plasma concentrations occur about 0.5-3 hrs after ingestion, but the rate and extent of absorption vary between patients and may vary inversely with the dose. After oral doses, some baclofen crosses the blood-brain barrier with a concentration in the cerebrospinal fluid (CSF) of about 12% of those in the plasma. Approximately 30% of baclofen is bound to plasma proteins. About 70-80% of the dose is excreted in the urine mainly as unchanged drug while about 15% is metabolized in the liver. The elimination t½ of baclofen is about 3-4 hrs in plasma and about 1-5 hrs in the CSF. Baclofen crosses the placenta and is distributed into breast milk.