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Baclofen
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| Systematic (IUPAC) name | |
| 4-amino-3-(4-chlorophenyl)-butanoic acid | |
| Identifiers | |
| CAS number | |
| ATC code | M03 |
| PubChem | |
| DrugBank | |
| ChemSpider | |
| Chemical data | |
| Formula | C10H12ClNO2 |
| Mol. mass | 213.661 g/mol |
| SMILES | & |
| Pharmacokinetic data | |
| Bioavailability | well absorbed |
| Protein binding | 30% |
| Metabolism | ? |
| Half life | 1.5 - 4 hours |
| Excretion | renal (70-80%) |
| Therapeutic considerations | |
| Pregnancy cat. |
C(US) |
| Legal status | |
| Routes | Oral, intrathecal |
Baclofen (brand names Kemstro and Lioresal) is a derivative of gamma-aminobutyric acid (GABA) primarily used to treat spasticity.
It is an agonist specific to mammalian but not fruit fly (Drosophila) GABAB receptors.[1][2] It is used for the treatment of spastic movement, especially in instances of spinal cord injury, spastic diplegia, multiple sclerosis, amyotrophic lateral sclerosis (Lou Gehrig's Disease) and trigeminal neuralgia. Its beneficial effects result from actions at spinal and supraspinal sites. Baclofen can also be used to treat hiccups. It has been shown to prevent rises in body temperature induced from the drug MDMA in rats.[1] A very benefitial property of baclofen is that tolerance does not seem to occur to any significant degree in that baclofen retains its therapeutic anti-spasmodic effects even after many years of chronic use.[2]
Contents |
History
Historically baclofen was designed to be a drug for epilepsy in the 1920s. The effect on epilepsy was disappointing but it was found that in certain patients spasticity decreased. Baclofen was and is still given orally with variable effects. In severely affected children, the oral dose is so high that side effects appear and the treatment loses its benefit. How and when baclofen came to be used in the spinal sac is not really clear but this is now an established method for the treatment of spasticity in many conditions. Recently some trials have been conducted in using Baclofen to treat cocaine addiction. While no final study has been released, people have said once they took Baclofen they felt their desire for cocaine plummet almost overnight. There is a report that baclofen has beneficial role in the management of reflux disease.[3]
Description of compound
Baclofen is a white (or off white) mostly odorless crystalline powder, with a molecular weight of 213.66 g/mol. It is slightly soluble in water, very slightly soluble in methanol, and insoluble in chloroform.
Pharmacokinetics
The drug is rapidly absorbed after oral administration and is widely distributed throughout the body. Biotransformation is low and the drug is predominantly excreted in the unchanged form by the kidneys.
Routes of administration
Baclofen can be administered either orally or intrathecally (directly into the cerebral spinal fluid). Intrathecal administration is often preferred in spasticity patients, as very little of the oral dose actually reaches the spinal fluid. Intrathecal administration is particularly used in patients with multiple sclerosis who have severe painful spasms which are not controllable by oral baclofen, or patients with spastic diplegia in whom management of spasticity is made easier by regular self-administering of the drug through its pump.
With pump administration, a test dose is given to assess the effect, and if successful a chronic intrathecal catheter is inserted and connected to a computer-controlled implanted pump. The reservoir in the pump can be replenished by percutaneous injection. These pump systems are quite sophisticated and expensive, so careful patient selection is required. In about 5% of patients, the intrathecal route has no effect on the nervous system.citation needed
Dosage
Baclofen therapy is usually started with an initial low dose of about 15 mg daily in divided doses and gradually titrated up in a stepwise fashion until symptomatic relief occurs. The usual maximum dose per day is 80 mg per day.[4]
Withdrawal syndrome
Discontinuation of baclofen can be associated with a withdrawal syndrome which resembles benzodiazepine withdrawal and alcohol withdrawal. Withdrawal symptoms are more likely if baclofen is used for long periods of time (more than a couple of months) and can occur from low or high doses. The severity of baclofen withdrawal depends on the rate at which baclofen is discontinued. Thus to minimise baclofen withdrawal symptoms the dose should be tapered down slowly when discontinuing baclofen therapy. Abrupt withdrawal is most likely to result in severe withdrawal symptoms. Acute withdrawal symptoms can be stopped by recommensing baclofen.[5]
Withdrawal symptoms may include auditory hallucinations, visual hallucinations, tactile hallucinations, delusions, confusion, agitation, delirium, disorientation, fluctuation of consciousness, insomnia, inattention, memory impairments, perceptual disturbances, anxiety, depersonalization, hypertonia, hyperthermia, formal thought disorder, psychosis, mania, mood disturbances, restlessness, and behavioral disturbances, tachycardia, seizures, tremors, autonomic dysfunction, hyperpyrexia, extreme muscle rigidity resembling neuroleptic malignant syndrome and rebound spasticity.[5][6]
Use in addiction & physical dependence
Baclofen has been shown to be as effective as diazepam in uncomplicated alcohol withdrawal syndrome.[7]
Overdose
Symptoms of a baclofen overdose include vomiting, weakness, drowsiness, slow breathing, seizures, unusual pupil size, and coma.
See also
References
- ^ http://www.mdma.net/baclofen/index.html,Baclofen prevents MDMA-induced rise in core body temperature in rats
- ^ Gaillard JM (May-Jun 1977). "Comparison of two muscle relaxant drugs on human sleep: diazepam and parachlorophenylgaba". Acta Psychiatr Belg 77 (3): 410–25. PMID 200069.
- ^ Zhang Q et al (2001). "Control of transient lower oesophageal sphincter relaxations and reflux by the GABAb agonist baclofen in patients with gastro-oesophageal reflux disease". Gut 50: 19-24.
- ^ "Kemstro (Baclofen) drug indications and dosage - prescription drugs and medications" 2. RxList. Retrieved on Sep 21, 2008.
- ^ a b Leo RJ; Baer D (Nov-Dec 2005). "Delirium Associated With Baclofen Withdrawal: A Review of Common Presentations and Management Strategies". Psychosomatics 46 (6): 503–507. doi:. PMID 16288128.
- ^ Grenier B, Mesli A; Cales J, Castel JP, Maurette P (1996). "[Severe hyperthermia caused by sudden withdrawal of continuous intrathecal administration of baclofen]". Ann Fr Anesth Reanim 15 (5): 659–62. PMID 9033759.
- ^ Addolorato G; Leggio L, Abenavoli L, Agabio R, Caputo F, Capristo E, Colombo G, Gessa GL, Gasbarrini G (Mar 2006). "Baclofen in the treatment of alcohol withdrawal syndrome: a comparative study vs diazepam". Am J Med 119 (3): 276.e13–8. doi:. PMID 16490478.
- Intrathecal Baclofen Therapy Cleveland Clinic Information Center. 15 June 2001.
- [3]
External links
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Wikipedia content modification information:
- This page was last modified on 1 October 2008, at 13:22.
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