Cyclobenzaprine (Flexeril) vs. amitriptyline (Elavil)

• Cyclobenzaprine and amitriptyline are used to treat different types of pain from different causes.
• Cyclobenzaprine is used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions.
• Amitriptyline may be used to treat nerve pain, but it is primarily used to treat depression.
• Brand names for cyclobenzaprine include Flexeril, Amrix, and Fexmid.
• Brand names for amitriptyline include Elavil and Endep.
• Cyclobenzaprine and amitriptyline belong to different drug classes. Cyclobenzaprine is a muscle relaxant and amitriptyline is a tricyclic antidepressant (TCA).
• Side effects of cyclobenzaprine and amitriptyline that are similar include blurred vision, dry mouth, and constipation.
• Side effects of cyclobenzaprine that are different from amitriptyline include drowsiness, fatigue, headaches, dizziness, nausea, unpleasant taste, nervousness, confusion, acid reflux, and abdominal pain or discomfort.
• Side effects of amitriptyline that are different from cyclobenzaprine include fast heart rate, urinary retention, sexual dysfunction, weight changes, and dizziness on standing (orthostatic hypotension).

Cyclobenzaprine is a muscle relaxant used with rest and physical therapy to relieve muscle spasms associated with acute painful muscle and skeletal conditions. It is only for short-term use of two or three weeks. Cyclobenzaprine relieves muscle spasm due to local problems, that is, problems in the muscle itself and not in the nerves controlling the muscles. Cyclobenzaprine is believed to achieve its beneficial effect through a complex mechanism within the nervous system, probably in the brainstem.

Amitriptyline is a tricyclic antidepressant (TCA) and is used for treating depression. Other TCAs include clomipramine (Anafranil), doxepin (Sinequan), imipramine (Tofranil), trimipramine (Surmontil), amoxapine (Amoxapine), desipramine (Norpramin), and protriptyline (Vivactil). Individuals with depression may have an imbalance in neurotransmitters, chemicals that nerves make and use to communicate with other nerves. Like all TCAs, amitriptyline increases levels of the neurotransmitter norepinephrine and serotonin, and blocks the action of acetylcholine, another neurotransmitter. It is believed that by restoring the balance of these different neurotransmitters in the brain that depression is alleviated.

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.

Amitriptyline

Sometimes troublesome side effects include:

• Fast heart rate
• Blurred vision
• Urinary retention
• Dry mouth
• Constipation
• Sexual dysfunction
• Weight gain or loss
• Low blood pressure on standing (orthostatic hypotension)

Rare side effects include:

• Rash
• Hives
• Seizures
• Hepatitis

Amitriptyline is used with caution in patients with seizures since it can increase the risk of seizures.

Amitriptyline also is used with caution in patients with prostate enlargement because of the risk of increasing the inability to urinate.

Amitriptyline can cause elevated pressure in the eyes of some patients with glaucoma.

If amitriptyline is discontinued abruptly, dizziness, headache, nausea, and restlessness may occur. Withdrawal symptoms may occur when even a few doses are missed. Therefore, it is recommended that the dose of antidepressants be reduced gradually when therapy is discontinued.

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.

Amitriptyline

Amitriptyline may be taken with or without food. The recommended adult dose is 100 to 300 mg daily in divided doses or at bedtime. The initial dose is 50 to 100 mg at bedtime that may be increased by 25 or 50 mg at bedtime as needed. The lowest effective dose should be used.

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

Amitriptyline

• Amitriptyline should not be used with monoamine oxidase inhibitors (MAOIs). High fever, convulsions, and even death can occur when these two types of drugs are used together.
• Epinephrine should not be used with amitriptyline, since together they can cause severe high blood pressure.
• Alcohol blocks the antidepressant action of amitriptyline but increases its sedative effect.
• Cimetidine (Tagamet) can increase blood levels of amitriptyline and its side effects by preventing the elimination of amitriptyline.

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

Amitriptyline

• Safety of amitriptyline in pregnancy and children is not established.
• Amitriptyline is secreted in human milk and potentially can adversely affect the nursing infant.

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

Amitriptyline

• Safety of amitriptyline in pregnancy and children is not established.
• Amitriptyline is secreted in human milk and potentially can adversely affect the nursing infant.