Relentus

Indications

• Painful Muscle Spasms: Effective for managing muscle spasms associated with spinal disorders (cervical and lumbar syndromes) and post-surgical recovery from procedures like herniated disc or hip osteoarthritis.
• Neurological Spasticity: Addresses spasticity resulting from neurological conditions such as multiple sclerosis, chronic myelopathy, degenerative spinal cord diseases, cerebrovascular accidents, and cerebral palsy.

Pharmacology

• Mechanism of Action: Tizanidine acts as a central muscle relaxant, targeting the spinal cord to inhibit excitatory amino acids that stimulate NMDA receptors. This results in reduced muscle tone and alleviation of spasms. Additionally, it provides moderate central analgesia.
• Pharmacodynamics: Tizanidine is beneficial for both acute muscle spasms and chronic spasticity, reducing resistance to passive movements and improving muscle strength. Its effectiveness and side effects are linked to plasma concentrations of the drug.

Dosage & Administration

• Initial Dosage: Start with 2 mg three times daily. Gradually adjust the dose based on individual needs and tolerability.
• Painful Muscle Spasms: Typically 2 to 4 mg three times daily, with an optional additional dose at night for severe cases.
• Neurological Spasticity: Initial dose should not exceed 6 mg daily, divided into three doses. Increase stepwise to a maximum of 36 mg daily.
• Special Populations: For pediatric patients, use is not recommended. In elderly patients, initiate treatment at the lowest dose and adjust carefully. In renal impairment, start with 2 mg daily and adjust as needed. Severe hepatic impairment is a contraindication.

Interactions

• CYP1A2 Inhibitors: Avoid using with strong CYP1A2 inhibitors like fluvoxamine or ciprofloxacin due to the risk of increased tizanidine levels and adverse effects.
• CYP1A2 Inducers: Avoid strong CYP1A2 inducers like rifampicin, which may reduce tizanidine effectiveness.
• Other Considerations: Monitor interactions with drugs that prolong QT intervals and avoid alcohol to prevent enhanced sedation and hypotension.

Contraindications

• Hypersensitivity: Contraindicated in individuals with known hypersensitivity to tizanidine.
• Severe Hepatic Impairment: Not recommended for patients with severe liver dysfunction.
• CYP1A2 Inhibitors: Avoid in combination with strong CYP1A2 inhibitors.

Side Effects

• Common: Includes somnolence, dizziness, dry mouth, and gastrointestinal disturbances. Higher doses may cause hypotension, bradycardia, muscular weakness, and more pronounced adverse effects.
• Serious: Monitor for severe reactions such as hallucinations and hepatitis.

Pregnancy & Lactation

• Pregnancy: Limited data available; use only if clearly needed.
• Lactation: Not recommended for breastfeeding due to potential excretion in milk.

Precautions & Warnings

• Hypotension: Monitor for low blood pressure, especially with CYP1A2 inhibitors and antihypertensive drugs.
• Withdrawal: Gradually taper off to avoid rebound hypertension and tachycardia.
• Hepatic Dysfunction: Regular liver function tests are recommended at higher doses.

Special Populations

• Renal Impairment: Start at 2 mg daily due to increased exposure.
• Hepatic Impairment: Use with caution; contraindicated in severe cases.
• Geriatrics: Limited data; start at low doses and adjust carefully.

Overdose Effects

Symptoms: May include nausea, hypotension, dizziness, and QT prolongation. Manage with activated charcoal and symptomatic treatment.

Therapeutic Class

Category: Centrally Acting Skeletal Muscle Relaxants

Storage Conditions

Storage: Keep in a dry place below 30°C and out of reach of children.