Cyclobenzaprine vs. Zanaflex

• Cyclobenzaprine and Zanaflex (tizanidine) are muscle relaxants used to relieve muscle spasms associated with painful muscle and skeletal conditions.
• Cyclobenzaprine is used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions while Zanaflex is used for the treatment and management of skeletal muscle spasticity due to chronic conditions such as multiple sclerosis or spinal cord injury.
• Brand names for cyclobenzaprine include Flexeril, Amrix, and Fexmid.
• Side effects of cyclobenzaprine and Zanaflex that are similar include dry mouth, fatigue, dizziness, constipation, and blurred vision.
• Side effects of cyclobenzaprine that are different from Zanaflex include drowsiness, headaches, nausea, unpleasant taste, nervousness, confusion, acid reflux, and abdominal pain or discomfort.
• Side effects of Zanaflex that are different from cyclobenzaprine include low blood pressure, sleepiness, and weakness.

Cyclobenzaprine is a muscle relaxant used with rest and physical therapy for short-term relief (up to two to three weeks) of muscle spasms associated with acute painful muscle and skeletal conditions. Cyclobenzaprine relieves muscle spasm when the spasm that results from local problems in the muscle itself and not from the nerves controlling the muscles. Cyclobenzaprine accomplishes its helpful effect through a complex mechanism within the nervous system, most likely in the brainstem.

Zanaflex (tizanidine) is a skeletal muscle relaxant used for the treatment and management of skeletal muscle spasticity, typically resulting from neurological problems. Spasticity may be due to multiple sclerosis or spinal cord injury. It works on alpha 2 receptors in the central nervous system (brain and spinal cord) and blocks nerve impulses from reaching muscles, which produces muscle relaxation.

Cyclobenzaprine

The most common side effects of cyclobenzaprine include:

• Drowsiness
• Dry mouth
• Fatigue
• Headaches
• Dizziness

Other reported side effects include:

• Nausea
• Constipation
• Blurred vision,
• Unpleasant taste
• Nervousness
• Confusion
• Acid reflux
• Abdominal pain or discomfort

Possible serious side effects include:

• Seizures
• Abnormal heart beats
• Stroke
• Heart attacks
• Heat stroke

Abrupt cessation after prolonged therapy may cause withdrawal symptoms such as headaches, nausea, and weakness.

Zanaflex

Common side effects of tizanidine include:

• low blood pressure,
• dry mouth,
• dizziness,
• sleepiness,
• weakness,
• fatigue,
• blurred vision, and
• constipation.

Cyclobenzaprine

The recommended dose of cyclobenzaprine dose is 5 or 10 mg three times daily using immediate release tablets or 15 or 30 mg once daily using extended release tablets.

Zanaflex

Initially take 2 - 4 mg by mouth every 6 to 8 hours for up to 3 doses in 24 hours. Increase by 2 to 4 mg until satisfactory response is achieved; however, the maximum dose is 36 mg per day.

Cyclobenzaprine

• Cyclobenzaprine is chemically related to the tricyclic class of antidepressants, for example, amitriptyline (Elavil, Endep), nortriptyline Pamelor). As such, it should not be taken with or within two weeks of any monoamine oxidase (MAO) inhibitor, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane). High fever, convulsions, and even death can occur when these drugs are used together.
• Cyclobenzaprine interacts with other medications and drugs that slow the brain's processes, such as
  • alcohol,
  • barbiturates,
  • benzodiazepines, for example, diazepam (Valium), lorazepam (Ativan), and
  • narcotics.

Zanaflex

Tizanidine should not be used with:

• ciprofloxacin (Cipro),
• amiodarone (Cordarone),
• cimetidine (Tagamet),
• oral contraceptives,
• acyclovir (Zovirax), and
• fluvoxamine (Luvox).

These medications can slow down the breakdown of tizanidine and lead to increased sedation, drowsiness and slowed reflexes.

Tizanidine should be used with caution with medications like:

• alprazolam (Xanax),
• clonazepam (Klonopin),
• diazepam (Valium),
• zolpidem (Ambien),
• oxycodone (Roxicodone),
• hydromorphone (Dilaudid),
• amitriptyline (Elavil),
• nortriptyline (Pamelor) and
• alcohol.

These medications can further increase the side effects of tizanidine.

Cyclobenzaprine

There are no adequate studies of cyclobenzaprine in pregnant women. However, studies in animals suggest no important effects on the fetus. Cyclobenzaprine therefore can be used in pregnancy if the physician feels that it is necessary.

It is not known whether cyclobenzaprine is secreted in milk. However, since it is related to the tricyclic antidepressants, some of which are excreted in breast milk, caution is advised in using this medication in women who are breastfeeding.

Zanaflex

There are no adequate studies done on tizanidine to determine safe and effective use in pregnant women.

It is not known whether tizanidine enters human milk. Because it is soluble in lipids, it might pass into breast milk.