Permanent delivery systems are available. A pump is surgically implanted into the abdominal wall and a catheter connects the pump to the intrathecal space, delivering a small but effective dose. Complications include pump malfunction and, rarely, spinal meningitis. Intrathecal baclofen is an effective long-term treatment for spasticity caused by MS, spinal cord injury, or cerebral spasticity. Lioresal is a commercially available licensed preparation.
Botulinum toxin is currently the favoured local technique and has largely replaced the others.
Botulinum is a potentially lethal neurotoxin produced by Clostridium botulinum, an anaerobic bacterium. Small doses of botulinum toxin are injected directly into the overactive muscle. Dose dependent relaxation of the target muscle is achieved within one week, with little or no effect on adjacent muscles. A irreversibly blocks neuromuscular transmission by preventing presynaptic calcium-mediated acetylcholine release at the neuromuscular junction. The injected muscle is paralysed until nerve sprouting forms new neuromuscular junctions.