Generic Name : Cyclobenzaprine.

Trade Name    : Multi-relax.

Drug Class      : Skeletal Muscle Relaxants.

Forms of The Drug

  1. Tablet: 5mg, 7.5mg, 10mg.
  2. Capsule: 15mg, 30mg.

Mechanism of Action

Cyclobenzaprine is a muscle relaxant medication primarily used for the management of acute musculoskeletal conditions characterized by muscle spasms, strains, and pain. Its mechanism of action involves modulation of neurotransmission within the central nervous system (CNS), particularly at the spinal cord level. Here’s how cyclobenzaprine works:

  1. Central Nervous System Effects: Cyclobenzaprine exerts its therapeutic effects primarily through its actions within the CNS. It acts centrally, rather than directly on skeletal muscle fibers, to produce muscle relaxation and alleviate symptoms associated with muscle spasms.
  2. Serotonin and Norepinephrine Reuptake Inhibition: Cyclobenzaprine has been shown to inhibit the reuptake of serotonin and norepinephrine, two neurotransmitters involved in the modulation of pain perception and muscle tone. By blocking the reuptake of these neurotransmitters, cyclobenzaprine increases their concentrations in the synaptic cleft, leading to enhanced neurotransmission and modulation of pain signals within the CNS.
  3. Alpha-Adrenergic Receptor Antagonism: Cyclobenzaprine exhibits antagonist activity at alpha-adrenergic receptors in the CNS. By blocking these receptors, cyclobenzaprine interferes with the transmission of sympathetic nervous system signals involved in muscle contraction and tone regulation. This alpha-adrenergic receptor antagonism contributes to the muscle relaxant effects of cyclobenzaprine.
  4. Anticholinergic Effects: Cyclobenzaprine possesses anticholinergic properties, albeit to a lesser extent compared to some other medications in its class. Anticholinergic effects include inhibition of acetylcholine at muscarinic receptors in the CNS and periphery. These effects may contribute to the muscle relaxant properties of cyclobenzaprine by reducing hyperactive reflexes and muscle spasms.
  5. Sedative Effects: Cyclobenzaprine has sedative properties and can cause drowsiness or dizziness, particularly at higher doses or when combined with other CNS depressants such as alcohol or benzodiazepines. The sedative effects of cyclobenzaprine may help alleviate discomfort and promote relaxation in individuals with acute musculoskeletal conditions.

Indications

  1. Muscle Spasms.
  2. Musculoskeletal pain associated with conditions such as strains, sprains, and other injuries to the muscles or bones.
  3. Musculoskeletal disorders: such as fibromyalgia, myofascial pain syndrome, or tension headaches.
  4. Adjunctive Therapy: such as physical therapy, rest, and analgesic medications.
  5. Postoperative Pain.

Contraindications

  1. Hypersensitivity
  2. Recent Myocardial Infarction.
  3. Arrhythmias
  4. Hyperthyroidism
  5. Severe Liver Impairment.
  6. Closed-Angle Glaucoma.
  7. Urinary Retention.

Side Effects

  1. Drowsiness (up to 39% immediate-release; 100% extended-release).
  2. Dry mouth (21-32%).
  3. Dizziness (3-11%).
  4. Pharyngitis (1-3%).
  5. Headache (1-5%).
  6. Fatigue (6%).
  7. Palpitations (6%).
  8. Bad taste in mouth (1-6%).
  9. Indigestion (4%).
  10. Blurred vision (3%).
  11. Constipation (1-3%).
  12. Asthenia (1-3%).
  13. Confusion (1-3%)
  14. Nausea (1-3%).
  15. Nervousness (1-3%).
  16. Arrhythmia.
  17. Hypotension.
  18. Palpitation.
  19. Syncope.
  20. Tachycardia.
  21. Vasodilation.
  22. Cardiac dysrhythmia (rare).
  23. Cholestasis (rare).
  24. Hepatitis.
  25. Jaundice.
  26. Anaphylaxis (rare).
  27. Immune hypersensitivity reaction.

Drug Interaction

  1. Central nervous system depressants, such as opioids, benzodiazepines, alcohol, and certain antipsychotic medications.
  2. Monoamine Oxidase Inhibitors (MAOIs).
  3. Serotonergic medications, such as selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants.
  4. Anticholinergic effects of other medications, such as tricyclic antidepressants, antihistamines, and antipsychotics.
  5. CYP3A4 Inhibitors: such as ketoconazole, erythromycin, and ritonavir.
  6. CYP3A4 Inducers: such as rifampin, phenytoin, and carbamazepine.

Precautions

  1. Pregnancy: Category B.
  2. Lactation: Cyclobenzaprine is excreted into human breast milk, and therefore caution is advised when considering its use in breastfeeding women.

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