Drugs for Neuromuscular Disorders

Neuromuscular Disorders: Drugs & Management

Overview of Muscle Spasms

• Definition: An involuntary contraction of a muscle or muscle groups, leading to a locked, contracted, and tight state with a fixed pattern of resistance.

• Impacts:

  • Significant pain, both in the locked state and especially when attempting to move past the resistance (sometimes impossible).

  • Diminished level of functioning if chronic.

  • Negative impacts on mobility and coordination.

• Common Causes:

  • Excessive use or overuse of a body part.

  • Local injury to skeletal muscle.

• Other Potential Causes:

  • Medication overdoses or overuses.

  • Certain underlying conditions (e.g., epilepsy).

  • Electrolyte imbalances.

  • Neurologic conditions.

  • Intermittent claudication (discussed later).

• Associated Symptoms: Often accompanied by inflammation and edema, particularly if related to acute, overuse, or chronic injury.

• Overall Goal: To help the affected muscle tissue relax and alleviate pain.

Types of Spasms

• Tonic Spasm:

  • Definition: A single, prolonged muscular contraction.

  • Example: A stiff neck, where the neck is locked in place without rapid spasming, characterized by a single, sustained contraction.

  • Connection: This term, and clonic spasm, relate to seizure disorders (e.g., tonic-clonic seizure), but can also occur locally.

• Clonic Spasm:

  • Definition: Multiple, rapidly repeating muscle contractions.

  • Example: Rapidly repeated muscle contractions in the back, especially after an improper ergonomic lift or heavy lifting, experienced locally.

• Dystonia:

  • Definition: A chronic neurologic disorder characterized by involuntary contractions that force the body into abnormal postures.

  • Symptoms & Effects:

    • Can be painful.

    • Significantly affects coordination and ambulation.

    • Impacts overall muscle tone in arms, legs, trunk, face, vocal cords, and neck.

    • Leads to increased risk of falls and decreased appropriate ambulation.

  • Connection: Recalled as a symptom of acute Extrapyramidal Symptoms (EPS) discussed in earlier neurologic lectures.

• Intermittent Claudication:

  • Cause: A circulatory problem where the lower extremity muscle tissue (e.g., calf muscle) does not receive sufficient oxygen.

  • Symptom: Muscle cramping when the affected tissue is recruited.

  • Note: While it presents as a musculoskeletal problem, its origin is cardiovascular and will be discussed further in the cardiovascular module.

• Spasticity:

  • Distinction from Muscle Spasm: Differs from muscle spasm in that it includes involuntary jerking movements, not necessarily constant, but triggered by movement or stimulation, in addition to tonic spasms.

  • Underlying Cause: Indicates a Central Nervous System (CNS) issue or injury.

    • Examples: Traumatic Brain Injury (TBI), Spinal Cord Injury (SCI), Cerebral Palsy, Multiple Sclerosis (MS), tumors, or lesions.

  • Symptoms: Very stiff muscles, marked increase in muscle tone, exaggerated deep tendon reflexes, tonic spasms, and fixed positions. Any slight movement out of these positions can trigger involuntary jerking movements.

  • Impact: Can significantly and negatively impact an individual's quality of life.

Neuromuscular Blockers

• Briefly mentioned as already covered in the anesthetics slide set and will not be re-discussed here.

Overall Treatment Goals for Neuromuscular Conditions

• Increase range of motion.

• Decrease pain.

• Improve Activities of Daily Living (ADLs) and enhance patient independence.

Pharmacotherapy Considerations

• Onset of Effect: Therapeutic effects may take several days to be noticeable.

• Safety Concerns:

  • Increased Fall Risk: Medications often increase fall risk due to their CNS depressant effects. Patients may already be at risk due to their condition, age, or comorbidities.

  • Caution with Elderly: Elderly patients are particularly vulnerable to:

    • Increased sedation.

    • Exacerbated effects due to polypharmacy.

    • Decreased ability to metabolize and eliminate drugs efficiently.

Non-Pharmacologic Interventions

These therapies are crucial and can be used as primary treatments or as adjuncts to pharmacotherapy.

• Patient positioning.

• Immobilization or support of affected limbs/extremities to prevent further issues and promote relaxation.

• Supervised exercises and physical therapy.

• Acupressure.

• Gentle massage.

• Heat or cold applications.

• Capsaicin (Red Pepper): A topical application that provides heat to affected areas, helping to relax muscle tissue.

Pharmacologic Agents for Neuromuscular Disorders

Drugs for neuromuscular conditions can act either centrally (on the CNS) or directly (at the neuromuscular junction and skeletal muscle).

I. Centrally Acting Skeletal Muscle Relaxants

• Mechanism: Affect the body at the CNS level.

• Cyclobenzaprine (Flexeril):

  • Uses: Primarily for acute musculoskeletal injury, such as low back pain, typically used in conjunction with physical therapy and analgesia.

  • Note: Not indicated for spasticity.

• Baclofen:

  • Uses: Effectively treats spasticity associated with Multiple Sclerosis (MS), spinal cord injury (SCI) or disease, and cerebral palsy.

II. Direct Acting Antispasmodics

• Mechanism: Work directly at the neuromuscular junction and the skeletal muscle itself.

• Dantrolene:

  • Uses: Primarily for spasticity in conditions such as cerebral palsy, Multiple Sclerosis (MS), spinal cord injury (SCI), and strokes.

  • Additional Critical Uses:

    • Treatment for Malignant Hyperthermia (MH), an adverse effect of certain general anesthetics.

    • Treatment for Neuroleptic Malignant Syndrome (NMS), an adverse effect of some antipsychotic agents.

  • Antidote: Serves as the antidote for both malignant hyperthermia and neuroleptic malignant syndrome.

  • Nursing Responsibility: Essential to obtain a thorough patient and family history regarding previous adverse effects to anesthesia to assess MH risk.

• Succinylcholine:

  • Uses: Typically used in Emergency Rooms (ER) or Operating Rooms (OR) to assist with intubation.

  • Administration: Generally administered by advanced practitioners; general nursing administration is typically not within scope unless additional advanced training is completed.

  • Adverse Effect: Can cause malignant hyperthermia.

General Nursing Considerations for Neuromuscular Drugs

• Mechanism of Action: While not fully understood for all, many involve some level of CNS depression.

• Patient Assessment:

  • Assess the patient's condition, symptoms, and level of consciousness.

• Patient Education:

  • Driving: Advise patients not to drive or operate heavy machinery until they understand how the medication affects them, due to potential sedation.

  • CNS Depressants: Instruct patients to avoid additional CNS depressants, including alcohol, to prevent exacerbated sedative effects and increased fall risk.

  • Fall Risk: Emphasize increased fall risk, especially for the elderly, where falls can lead to debilitating long-term consequences.

  • Side Effects: Educate patients to report any symptoms indicative of potential adverse effects on kidney function, liver function, or gastrointestinal issues (e.g., constipation).

• Therapeutic Goals:

  • Ensure the patient is achieving their therapeutic goals, assessing improvements in pain and motor function.

  • Encourage self-monitoring of therapeutic effects and undesired side effects.

• Adjunctive Therapies: Encourage the use of non-pharmacologic strategies in conjunction with medications to enhance outcomes.

• Safety and Mobility:

  • Follow safety and activity guidelines, especially for patients with limited mobility.

  • Implement treatment plans to prevent further injury and help patients achieve their mobility goals safely.

Conclusion

• Complexity: Disorders affecting movement are challenging to treat due to their widespread impact on other body systems.

• Holistic Approach: The body is an interconnected unit; movement impairment can affect numerous physiological processes.

• Combined Modalities: Non-pharmacologic therapies, when used with medications, often lead to superior outcomes.

• Ultimate Goal: To minimize pain and enable patients to function as independently as possible, tailoring goals based on the specific nature of the condition (e.g., temporary muscle strain vs. chronic progressive disease).