Spasticity, characterized by muscle stiffness, tightness, and involuntary spasms, is a frequent and disabling symptom of both multiple sclerosis (MS) and spinal cord injury (SCI). It results from damage to the central nervous system that disrupts nerve signals, causing muscles to become overactive. The optimal treatment approach is highly individualized, considering factors like the severity of spasticity, its distribution (focal or generalized), and the patient's tolerance for medication side effects. While physical therapy and stretching are foundational, medication is often a cornerstone of a comprehensive management plan.
Baclofen: The most common oral choice
Baclofen is often the first-line oral muscle relaxant prescribed for spasticity resulting from MS or SCI. It works by mimicking the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), acting on GABA-B receptors in the spinal cord. This action helps to inhibit reflexes and reduce muscle spasticity and spasms.
Oral administration and common side effects
- Administration: Baclofen is typically taken orally several times a day in tablet, solution, or dissolvable granule form.
- Side Effects: Common adverse effects include drowsiness, dizziness, weakness, nausea, and headache.
- Important consideration: Patients must never stop taking baclofen abruptly, as this can cause severe withdrawal symptoms, including seizures. The dosage must be tapered down slowly under a doctor's supervision.
Tizanidine: An alternative oral agent
Tizanidine is another centrally acting oral muscle relaxant that is FDA-approved for spasticity from MS and SCI. It functions as an alpha-2 adrenergic agonist in the central nervous system, reducing the release of excitatory amino acids in spinal interneurons.
Efficacy and side effect profile
- Administration: Tizanidine is available as tablets and capsules, usually taken two or three times per day.
- Comparative efficacy: Clinical studies have found tizanidine to be roughly equivalent to baclofen in reducing spasticity. Some reports suggest it may cause less muscle weakness than baclofen.
- Side Effects: Common side effects include dry mouth, drowsiness, dizziness, and low blood pressure. Liver function should be monitored during treatment.
Other oral muscle relaxants
Several other oral medications are used for spasticity, though typically as second-line or adjunctive therapies.
- Diazepam (Valium): A benzodiazepine that enhances the effect of GABA-A receptors. It is effective but has a high potential for tolerance and dependence, so it is generally reserved for short-term use.
- Dantrolene (Dantrium): Unlike other relaxants, dantrolene acts directly on skeletal muscle fibers to reduce contraction by inhibiting calcium release. A major concern is potential liver toxicity, requiring regular monitoring.
Advanced therapies for targeted or severe spasticity
Botulinum Toxin injections
For focal spasticity—affecting only a limited area like an arm or a leg—Botulinum toxin type A (BoNT-A), commonly known as Botox, is a highly effective treatment.
- Mechanism: The toxin is injected directly into specific muscles, where it temporarily blocks the release of acetylcholine, the neurotransmitter responsible for muscle contraction.
- Duration: The effects last for several months, after which repeat injections are necessary.
- Benefit: It can provide localized relief without the systemic side effects of oral medications.
Intrathecal Baclofen therapy
For patients with severe, widespread spasticity that does not respond to oral medications or who experience intolerable side effects, Intrathecal Baclofen (ITB) therapy is an option.
- Mechanism: A surgically implanted pump delivers a precise, continuous dose of liquid baclofen directly into the spinal fluid.
- Benefit: This allows for a much lower dose to be used compared to oral baclofen, significantly reducing systemic side effects like sedation and weakness.
- Procedure: The pump requires refills every few months during a simple office visit.
Non-pharmacological interventions
Medication alone is rarely sufficient. A holistic treatment plan for spasticity should also include non-pharmacological interventions:
- Physical and occupational therapy to maintain range of motion, strength, and function.
- Use of orthoses, casts, or braces to properly position limbs and prevent contractures.
- Application of heat or cold therapy to temporarily ease muscle tension.
Comparison of common oral muscle relaxants
| Feature | Baclofen (Lioresal) | Tizanidine (Zanaflex) | Diazepam (Valium) |
|---|---|---|---|
| Mechanism of Action | Central, GABA-B agonist in spinal cord | Central, alpha-2 adrenergic agonist in brainstem | Central, GABA-A agonist |
| Common Side Effects | Drowsiness, dizziness, weakness, nausea | Dry mouth, drowsiness, dizziness, low blood pressure | Sedation, fatigue, dependence risk |
| Administration | Oral (tablet, solution, granules), Intrathecal | Oral (tablet, capsule) | Oral (tablet), Parenteral |
| Long-term Use | First-line for chronic spasticity; intrathecal for severe cases | Effective for chronic spasticity, often second-line | Limited due to tolerance and dependence |
| Withdrawal Risk | Significant, requires careful tapering | Less significant, requires tapering | High potential for physical dependence |
Conclusion
Selecting the most appropriate medication for managing MS or SCI-related spasticity is a tailored process. Baclofen and tizanidine are the most frequently used oral muscle relaxants, offering similar effectiveness but with different side effect profiles. Baclofen is often the first choice, but tizanidine may cause less muscle weakness in some patients. For localized issues, botulinum toxin injections provide targeted relief, while intrathecal baclofen is a powerful option for severe, widespread cases. Combining these pharmacological options with non-drug therapies is crucial for a comprehensive and effective treatment strategy. Close collaboration with a healthcare team is essential to monitor progress, adjust dosages, and manage side effects.
