MYLOSPAS

Indications

• Muscle spasms
• Musculoskeletal pain
• Pain associated with acute musculoskeletal conditions

Dosage

Children: Refer to the BNF for Children for appropriate dosing information for paediatric patients.

Adults: Refer to the BNF for specific dosing guidelines, as dosages may vary based on individual patient needs and clinical context.

Mechanism of action

The mechanism of action of methocarbamol is thought to depend on its central nervous system depressant activity, which may involve blocking spinal polysynaptic reflexes, decreasing nerve transmission in spinal and supraspinal polysynaptic pathways, and prolonging the refractory period of muscle cells. It does not directly affect muscle contractions or nerve fibers, acting instead within the CNS to produce its muscle relaxant effects.

Pharmacodynamics

Methocarbamol has been demonstrated to block spinal polysynaptic reflexes and decrease nerve transmission in both spinal and supraspinal pathways. It prolongs the refractory period of muscle cells, contributing to its muscle relaxant effects. While its exact pharmacodynamics are not fully understood, the CNS depressant effects are a significant aspect of its therapeutic action. Additionally, methocarbamol has shown effectiveness in preventing convulsions in animal studies following electric shock.

Pharmacokinetics

Methocarbamol is well absorbed following oral administration, with peak plasma concentrations typically occurring within 1 to 2 hours. It is metabolized in the liver, with metabolites excreted primarily via the urine. The half-life of methocarbamol can vary, but it generally ranges from about 1 to 2 hours. The drug's effects can be influenced by factors such as age, liver function, and concomitant medications.

Contra-indications

• Active peptic ulceration
• Local infection (with intrathecal use)
• Systemic infection (with intrathecal use)

Adverse effects

• Drowsiness
• Dizziness
• Confusion
• Dry mouth
• Constipation
• Diarrhea
• Depression
• Insomnia
• Chills
• Dyspnea
• Fever
• Hypersalivation
• Asthenia
• Appetite decreased

Interactions

• Alcohol (enhanced drowsiness)
• Other CNS depressants (may enhance sedative effects)

Precautions

• Use with caution in patients with cerebrovascular disease
• Diabetes
• Epilepsy
• History of peptic ulcer
• Elderly patients
• Malnutrition
• Coagulation disorders (increased risk of post-surgical complications)

Pregnancy

Safety during pregnancy has not been established; use only if clearly needed and after careful consideration of risks and benefits.

Breast-feeding

It is not known if methocarbamol is excreted in human milk; caution is advised.

Storage

Store below 25°C. Protect from light. Keep out of reach of children.

Formulations

• Tablet 10mg
• Solution for injection 10mg/20ml
• Oral liquid formulation

Mechanism of action

The mechanism of action of methocarbamol is thought to be dependant on its central nervous system depressant activity. This action may be mediated through blocking spinal polysynaptic reflexes, decreasing nerve transmission in spinal and supraspinal polysynaptic pathways, and prolonging the refractory period of muscle cells. Methocarbamol has been found to have no effect on contraction of muscle fibres, motor end plates, or nerve fibres. Precise mechanism of action has not been determined. These agents act in the central nervous system (CNS) rather than directly on skeletal muscle. Several of these medications have been shown to depress polysynaptic reflexes preferentially. The muscle relaxant effects of most of these agents may be related to their CNS depressant (sedative) effects. /Skeletal Muscle Relaxants/

Pharmacodynamics

Methacarbamol is a skeletal muscle relaxant with an unknown mechanism of action. Methacarbamol has been shown to block spinal polysynaptic reflexes, decrease nerve transmission in spinal and supraspinal polysynaptic pathways, and prolong the refractory period of muscle cells. Methocarbamol does not act as a local anesthetic upon injection. In animal studies, methocarbamol also prevents convulsions after electric shock.