Drowsiness baclofen

Baclofen is a GABA agonist at GABA B receptors and it has a presynaptic inhibitory function by reducing calcium influx. Its indication is increased extensor tone and clonus. Intrathecal administration may control severe spasticity pain. It is used for the treatment of spastic movement, especially in instances of spinal cord injury, spastic diplegia, multiple sclerosis and amyotrophic lateral sclerosis. Its central nervous system effects include drowsiness, somnolence and seizure activity in epileptic patients. 

Baclofen is at least as effective as diazepam in reducing spasticity and causes less sedation. In addition, baclofen does not reduce overall muscle strength as much as dantrolene. It is rapidly and completely absorbed after oral administration and has a plasma half-life of 3-4 hours. Dosage is started at 15 mg twice daily, increasing as tolerated to 100 mg daily. Adverse effects of this drug include drowsiness however, patients become tolerant to the sedative effect with chronic administration. Increased seizure activity has been reported in epileptic patients. Therefore, withdrawal from baclofen must be done very slowly. 

Clinical trials with oral tizanidine report comparable efficacy in relieving muscle spasm to diazepam, baclofen, and dantrolene. However, tizanidine produces a different spectrum of adverse effects, including drowsiness, hypotension, dry mouth, and asthenia. The dosage requirements vary markedly among patients, and individual dosage titration is necessary to achieve an optimal clinical effect. 

Adverse Effects. When initiating baclofen therapy, the most common side effect is transient drowsi-... 

As 70% of baclofen is excreted unchanged in the urine (29), accumulation and overdosage of baclofen can occur in patients with end-stage renal disease. Confusion, drowsiness, and coma after standard doses have been reported (30). In addition, abdominal pain was a common adverse effect of baclofen in patients with severe renal insufficiency (31). Toxic reactions characterized by a psychotic syndrome and myoclonus have also been reported (32). Patients with severely impaired renal function typically present with altered consciousness after very small doses of baclofen (31). Symptoms of overdose may resolve after hemodialysis (30,31). 

Side effects of dantrolene, baclofen and tizanidine are similar, being motor incoordination, drowsiness, dizziness, weakness, fatigue and gastrointestinal disturbances. 

Toxicity The sedation produced by diazepam is significant but milder than that produced by other sedative-hypnotic drugs at doses that induce equivalent muscle relaxation. Baclofen produces less sedation than diazepam. Dantrolene causes significant muscle weakness but less sedation than either diazepam or baclofen. Tizanidine may cause drowsiness and hypotension. 

Placebo-controlled studies In a doubleblind, placebo-controlled study of smoking reduction in 60 smokers, who were given baclofen titrated upwards to 20 mg qds, the most common adverse reaction during baclofen treatment was transient drowsiness however, there were no differences between the groups in mild, moderate, or severe sedation [42 ]. 

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