Cyclobenzaprine (Flexeril) vs. carisoprodol (Soma)

• Cyclobenzaprine and carisoprodol are muscle relaxants used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions.
• Brand names for cyclobenzaprine include Flexeril, Amrix, and Fexmid.
• A brand name for carisoprodol is Soma.
• Side effects of cyclobenzaprine and carisoprodol that are similar include drowsiness, headaches, dizziness, and nervousness.
• Side effects of cyclobenzaprine that are different from carisoprodol include dry mouth, fatigue, nausea, constipation, blurred vision, unpleasant taste, confusion, acid reflux, and abdominal pain or discomfort.
• Side effects of carisoprodol that are different from cyclobenzaprine include agitation, tremor, irritability, sleep problems (insomnia), fainting, abnormal heart beat, seizures, and depression.
• Do not stop using carisoprodol suddenly after long-term use, or you could have unpleasant withdrawal symptoms.

Cyclobenzaprine is a muscle relaxant used along with rest and physical therapy for short-term relief only (up to 2 or 3 weeks) of muscle spasms associated with acute painful muscle and skeletal conditions. Cyclobenzaprine relieves muscle spasm when it is due to local problems within the muscle and not due to problems in the nerves controlling the muscles. Cyclobenzaprine is believed to accomplish its beneficial effect through a complex mechanism within the nervous system, probably in the brainstem.

Carisoprodol is an oral muscle relaxant used together with rest and physical therapy for the short-term relief of acute painful muscle and skeletal conditions in adults. It is only used for 2 to 3 weeks. Its exact mechanism of action is unknown. It may work by altering communication among nerves in parts of the brain that control the sensation of pain and in the spinal cord.

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 heartbeats
• Stroke
• Heart attacks
• Heat stroke

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

Carisoprodol

The most common side effects of carisoprodol are:

• Headache
• Drowsiness
• Dizziness
• Agitation
• Nervousness
• Tremor
• Irritability
• Inability to sleep
• Fainting
• Abnormal heartbeat
• Seizures
• Depression

Serious side effects of carisoprodol include:

• Hives (angioedema)
• Serious allergic reactions (anaphylaxis)
• Seizures
• Abuse
• Fainting
• Low blood pressure

Carisoprodol is not a controlled substance. Patients may become dependent on carisoprodol, and discontinuation after long-term use may cause withdrawal symptoms.

Cyclobenzaprine

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

Carisoprodol

• The recommended dose of carisoprodol is 250 or 350 mg three times daily and at bedtime.
• The recommended treatment duration is 2 to 3 weeks.
• To avoid withdrawal symptoms, carisoprodol should be stopped gradually if it has been used for a long duration.

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 inhibitor (MAOI) -- 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)
  • narcotics

Carisoprodol

• Carisoprodol interacts with other medications and drugs that slow the brain's processes, accentuating their effects and causing drowsiness, such as:
  • alcohol,
  • barbiturates,
  • benzodiazepines -- for example, lorazepam (Ativan)
  • narcotics
• Omeprazole (Prilosec) and fluvoxamine (Luvox) may reduce the elimination of carisoprodol, leading to increased side effects.
• St. John's Wort and rifampin (Rifadin) increase the elimination of carisoprodol, possibly resulting in a reduced effect.

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 doctor deems 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, women who are breastfeeding should use caution with this medication.

Carisoprodol

• There are no adequate studies of carisoprodol in pregnant women.
• Carisoprodol accumulates in breast milk in concentrations twice those in the mother's blood. The effects of carisoprodol on the infants of lactating mothers are unknown. Therefore, women who are breastfeeding should use caution when using carisoprodol.