APO-BACLOFEN

What it is

APO-BACLOFEN contains baclofen, a gamma-aminobutyric acid derivative, as a racaemic mixture of the R(-) and S(+) isomers. The tablets are available in 10 mg and 25 mg strengths. Baclofen is an effective antispastic agent with a spinal site of action, and its mechanism of action and pharmacological properties differ from those of other antispastic agents.

Approved indications

— Suppression of voluntary muscle spasm in multiple sclerosis. — Suppression of voluntary muscle spasm in spinal lesions of traumatic, infectious, degenerative, neoplastic and unknown origin, causing skeletal hypertonus. — Suppression of voluntary muscle spasm in spinal lesions of traumatic, infectious, degenerative, neoplastic and unknown origin, causing spastic and dyssynergic bladder dysfunction.

Dosing overview

Treatment should always be started in hospital, using small doses which are then gradually increased in a stepwise manner. Treatment is typically started with a dose of 5 mg three times daily, subsequently increased at 3-day intervals by 5 mg three times daily until the optimum response has been attained. The optimum dosage generally ranges from 30 mg to 75 mg daily, although occasionally in hospitalised patients daily doses up to 100 mg may be necessary. In patients with impaired renal function or undergoing chronic haemodialysis, low doses of approximately 5 mg daily should be used.

Key safety warnings

Patients suffering from psychotic disorders, schizophrenia, depressive or manic disorders or confusional states should be treated cautiously and kept under careful surveillance. Suicide and suicide-related events have been reported in patients treated with baclofen. In most cases, patients had additional risk factors including alcohol use disorder, depression and/or a history of previous suicide attempts. Close supervision of patients with additional risk factors for suicide should accompany drug therapy. Caution is needed in patients with epilepsy or other convulsive conditions, cortical or subcortical brain damage or significant EEG abnormalities, since ingestion of baclofen may cause deterioration of seizure control and EEG changes and may precipitate convulsions. Cases of encephalopathy have been reported in patients treated with baclofen. Symptoms included somnolence, depressed level of consciousness, confusion, myoclonus and coma which are usually reversible after treatment discontinuation. If any signs or symptoms of encephalopathy are observed, baclofen should be discontinued. Upon abrupt withdrawal of baclofen, especially after long-term medication, anxiety and confusional states, delirium, hallucinations, psychotic disorders, mania, paranoia, convulsion (status epilepticus), dyskinesia, tachycardia, hyperthermia and temporary aggravation of spasticity and hypertonia have been reported. Discontinuation of treatment should always be gradual by successively reducing the dosage over a period of approximately 1 to 2 weeks, except in overdose-related emergencies or where serious adverse effects have occurred. Cases of misuse, abuse and dependence have been reported with baclofen. Caution should be exercised in patients with a history of substance abuse and the patient should be monitored for symptoms of baclofen misuse, abuse or dependence such as dose escalation, drug-seeking behaviour and development of tolerance.

Contraindications

APO-BACLOFEN is contraindicated in patients with known hypersensitivity to baclofen or to any of the components of the formulation.

PBS listing

The 25 mg tablet is listed on the PBS with 2 items under both unrestricted and restricted categories at an ex-manufacturer price of A$18.03. The 10 mg tablet is listed on the PBS with 2 items under both unrestricted and restricted categories at an ex-manufacturer price of A$8.25.

Regulatory history

APO-BACLOFEN 25 mg and 10 mg tablets were first listed on the ARTG on 1 March 2001. In July 2017, the PBAC recommended a new strength of baclofen (40 mg in 20 mL ampoule) for the same indication of severe chronic spasticity.