Brief Basic Baclofen Facts:
Baclofen is a selective GABA B receptor agonist causing the release of GABA.
Released in 1974 as a centrally acting muscle relaxant for spasticity.
Well absorbed orally with peak levels in 1-2 hours after ingestion. It is active in the CNS at lower levels than in plasma.
The dose for suppression of alcohol cravings is typically higher than that required for spasticity although for both indications the dose can vary from 30-300mg per day.
Mechanism of action:
Baclofen attaches to the GABA B receptors in the brain and spinal cord, causing the release of GABA, the CNS’s major inhibitory neurotransmitter. The mechanism of the effects on alcohol craving and anxiety are poorly understood.
The plasma half life of baclofen is around 4 hours. This means that it must be given multiple times a day to have a continuous effect. The most common regime is three times daily during waking hours.
Around 80% is renal excretion, largely as the unchanged drug. Only about 15% is metabolised in the liver to an inactive metabolite. The remaining 5% is excreted unchanged in the faeces.
Baclofen has been approved for use in Australia by the Therapeutic Goods Association (TGA) so it can be prescribed by medical practitioners in Australia. The TGA listing doesn’t restrict or set the indications for which baclofen can be prescribed. This is at the discretion of individual prescribers.
PBS status and Cost:
Baclofen is not subsidised by the Pharmaceutical Benefits Scheme (PBS) for use in alcohol addiction treatment so patients pay the full cost on a private script.
This is not a big issue because baclofen is very affordable with cheap generics available. A script for 100 x 10mg tablets will cost around $15 from discount chemists and around $25 elsewhere. There are also 25mg baclofen tablets available for patients who take higher doses. The price for 100 x 25mg is $28 – $38, the lower price available at discount chemists.