Drug Class Description

Generic Name

Drug Description

Presentation

Indications

Baclofen is indicated for:

1) The relief of spasticity of voluntary muscle resulting from disorders such as multiple sclerosis and other spinal lesions, including tumours of the spinal cord, motor neurone disease, syringomyelia, transverse myelitis and traumatic partial section of the spinal cord.

2) Adults and children in the relief of spasticity of voluntary muscle arising from conditions such as cerebral palsy, cerebrovascular accidents, traumatic head injury and meningitis.

Treatment with Baclofen should not be initiated until the spastic state has become stabilised and it should be administered selectively; it is most likely to be of benefit to patients whose spasticity constitutes a handicap to activities or physiotherapy.

Paediatric population

Baclofen is indicated in patients 0 to <18 years for the symptomatic treatment of spasticity of cerebral origin, especially where due to infantile cerebral palsy, as well as following cerebrovascular accidents or in the presence of neoplastic or degenerative brain disease.

Baclofen is also indicated for the symptomatic treatment of muscle spasms occurring in spinal cord diseases of infectious, degenerative, traumatic, neoplastic, or unknown origin such as multiple sclerosis, spastic spinal paralysis, amyotrophic lateral sclerosis, syringomyelia, transverse myelitis, traumatic paraplegia or paraparesis, and compression of the spinal cord

Adult Dosage

Before commencing treatment the overall extent of clinical improvement that the patient may be expected to achieve must be realistically assessed. Careful titration of dosage is essential (particularly in the elderly) until the patient is stabilised. If the initial dosage is too high or if the dosage is increased too rapidly, side-effects may occur. This is particularly relevant if the patients is ambulant in order to minimise muscle weakness in the unaffected limbs or where spasticity is necessary for support.

Adults:

The following gradually incremented dosage regime is suggested but may need adjustment to suit individual patient requirements.

5mg three times daily for three days.

10mg three times daily for three days.

15mg three times daily for three days.

20mg three times daily for three days.

Satisfactory control of symptoms is usually obtained with doses up to 60mg daily but a careful adjustment is often necessary to meet the requirements of each individual patient. Dosage may be slowly increased where necessary to a maximum daily dose of not more than 100mg unless the patient is in hospital under careful medical supervision. Small frequent dosage regimes may prove to be more beneficial in some cases than larger spaced doses. Additionally, some patients may benefit from the administration of Baclofen at night only in order to counteract painful flexor spasm. Similarly, a single dose given approximately 1 hour prior to the performance of specific tasks such as washing, shaving, dressing and physiotherapy will often improve mobility.

Once the maximum recommended dosage has been reached and a therapeutic effect is not apparent within 6 weeks a decision should be made whether to continue treatment with Baclofen.

Patients with impaired renal function:

In patients with impaired renal function or undergoing chronic haemodialysis, a particularly low dosage of Baclofen should be selected ie approximately 5mg daily.

Patients with spastic states of cerebral origin:

Unwanted effects are more likely to occur in these patients. It is therefore recommended that a very cautious dosage schedule be adopted and that patients be kept under appropriate surveillance.

Child Dosage

Paediatric population (0 to <18 years):

Treatment should usually be started with a very low dose (corresponding to approximately 0.3 mg/kg a day), in 2-4 divided doses (preferably in 4 divided doses).

The dosage should be raised cautiously, at about 1 week intervals, until it becomes sufficient for the child's individual requirements. The usual daily dosage for maintenance therapy ranges between 0.75 and 2 mg/kg body weight. The total daily dose should not exceed a maximum of 40 mg/day in children below 8 years of age. In children over 8 years of age a maximum daily dose of 60 mg/day may be given.

Baclofen tablets are not suitable for use in children below 33 kg body weight.

Elderly Dosage

Elderly:

Elderly patients may be more susceptible to side-effects, especially during initial therapy. Small doses should therefore be used at the start of treatment, the dose being titrated gradually against the response under careful supervision. There is no evidence that the eventual average maximum dosage differs from that in younger patients.

Contra Indications

• Hypersensitivity to Baclofen or any of the excipients.

• Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

• Active peptic ulceration as Baclofen stimulates gastric acid secretion.

• Porphyria.

Special Precautions

• Severe psychiatric disorders may be exacerbated by treatment with Baclofen. Patients suffering from these conditions should therefore be treated cautiously and kept under close surveillance.

• Baclofen may also exacerbate epileptic manifestations but can be employed provided appropriate supervision and adequate anticonvulsive therapy are maintained.

• Baclofen should be used with extreme care in patients already receiving antihypertensive therapy (see “Interactions”).

• Baclofen should be used with caution in patients suffering from cerebrovascular accidents or from respiratory, hepatic or renal impairment.

• Baclofen stimulates gastric acid secretion and should be used with caution in patients with a history of peptic ulceration.

• Since under treatment with Baclofen neurogenic disturbances affecting emptying of the bladder may show an improvement, whereas in patients with pre-existing sphincter hypertonia acute retention of urine may occur, the drug should be used with caution in such patients.

• Since in rare instances elevated SGOT, alkaline phosphatase and glucose levels in serum have been recorded, appropriate laboratory tests should be performed in patients with liver diseases or diabetes mellitus in order to ensure that no drug induced changes in these underlying diseases have occurred.

• Withdrawal: Anxiety and confusional states, hallucinations, psychotic, manic or paranoid states, convulsions (status epilepticus), tachycardia and as rebound phenomenon temporary aggravation of spasticity have been reported with abrupt withdrawal of Baclofen, especially after long term medication. Treatment should always (unless serious adverse effects occur) therefore, be gradually discontinued by successively reducing the dosage over a period of about 1-2 weeks.

There is very limited clinical data on the use of Baclofen in children under the age of one year. Use in this patient population should be based on the physician's consideration of individual benefit and risk of therapy.

Interactions

• Alcohol, anxiolytics and hypnotics: Alcohol and other CNS depressants may exacerbate the CNS effects of baclofen (daytime sedation, drowsiness) and should be avoided.

• Anaesthetics: Pre-treatment with baclofen may prolong the duration of fentanyl anaesthesia.

• Antidepressants, tricyclic: Tricyclic antidepressants can enhance the muscle relaxant effects of baclofen, resulting in profound muscle hypotonia so caution should be used if baclofen and tricyclic antidepressants are used concomitantly. In addition, tricyclic antidepressants can cause sedation and drowsiness which may be additive to the side effects of baclofen.

• Antihypertensives and diuretics: The hypotensive activity of baclofen may be potentiated by concomitant treatment with antihypertensive agents and diuretics. It may be necessary to adjust the dosage if baclofen is given to patients receiving antihypertensive therapy.

• Dopaminergics: It is recommended that levodopa and baclofen should not be given concomitantly. Reports of hallucination, confusion, headache and nausea developing in patients with parkinsonism shortly after baclofen was added to their medication. The interaction was thought to be due to an exacerbation of the side effects due to baclofen.

• Lithium: Patients receiving lithium and baclofen concomitantly should be monitored for severe aggravation of hyperkinetic symptoms, especially in patients with Huntington's chorea.

• Memantine: Memantine may modify the effects of baclofen.

• NSAIDs: Because of their potential adverse effect on renal function, NSAIDs may indirectly be associated with decreased excretion of baclofen.

Adverse Reactions

Unwanted effects occur mainly at the start of treatment, if the dosage is raised too rapidly, if large doses are employed, or in elderly patients. They are often transitory and can be attenuated or eliminated by reducing the dosage; they are seldom severe enough to necessitate withdrawal of the medication.

• Central nervous system: Particularly at the start of treatment, unwanted effects such as daytime sedation, drowsiness, and nausea may frequently occur. Also occasionally encountered are dryness of the mouth, respiratory depression, light-headedness, lassitude, exhaustion, mental confusion, dizziness, retching, vomiting, headache and insomnia.

Should nausea persist following a reduction in dosage, it is recommended that Baclofen be ingested with food or a milk drink.

• Neurological and/or psychiatric manifestations which have occasionally or rarely been reported include: euphoria, depressive states, paraesthesia, myalgia, muscular weakness, ataxia, tremor, nystagmus, accommodation disorders, hallucinations, nightmares. It is often difficult to distinguish between these manifestations and those of the disease under treatment. Lowering of the convulsion threshold and attacks of convulsions may possibly occur, particularly in epileptic patients.

• Gastrointestinal tract: Frequently nausea. Occasionally, mild gastrointestinal disturbances (constipation, diarrhoea).

• Cardiovascular system: Occasionally, hypotension, cardiovascular depression.

• Urogenital system: Occasionally or rarely, dysuria, frequency of micturition and enuresis are reported frequently. It is often difficult to distinguish between these manifestations and those of the disease under treatment.

• Other unwanted effects: In rare or isolated cases visual disturbances, alterations in the taste sensation, hyperhidrosis, skin rash, deterioration in liver function tests. There have been rare reports of hypothermia.

Certain patients have shown increased spasticity as a paradoxical reaction to the medication.

An undesirable degree of muscular hypotonia - making it more difficult for patients to walk or fend for themselves - may occur and can usually be relieved by re-adjusting the dosage (ie by reducing the doses given during the day and possibly increasing the evening dose).

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