What is phenol?

Phenol is an anesthetic drug given by injection (a shot). This drug is used in patients with spasticity where the muscle(s) involved are overactive. Phenol acts as a chemical neurolytic (neuh-ro-LIT-ick) agent. This means that it works as a nerve block. It temporarily destroys a portion of the nerve to prevent the overactivity.

What type of patient gets Phenol therapy?

Phenol therapy is often the appropriate treatment for individuals with spasticity that limits what they can do or that causes pain. Phenol has been used to control muscle over activity in the arms or legs, mainly in adults who have had a stroke or brain trauma (injury to the brain). Phenol has also been used in children with cerebral palsy. Phenol therapy is generally not done for women who are pregnant or breastfeeding, or for people with certain diseases of the nerves and muscles.

How does it work?

Phenol acts by destroying the nerve pathways that are involved with spasticity of that specific muscle group. These nerve pathways eventually grow back. The advantage of using phenol is that you see the effect immediately after the treatment. The effects of treatment can last from six to 36 months.

What results can I expect?

It is important to understand that phenol is an effective, ongoing treatment for the relief of symptoms only. It is not a cure. Because every patient is different, the degree of relief will vary from person to person. Patients should resume activity slowly and carefully following the administration of phenol. Physical or occupational therapy may be recommended after injection in order to get the best results.

What side effects might I experience?

The most common side effects are:

  • Pain during injection
  • Dysethesia (a burning, tingling sensation)
  • Swelling of the arm or leg where the drug was injected


Less common side effects include skin sloughing (rubbing off), motor weakness, sensory loss, and wound infection. If you notice any of these you should call your doctor.

Serious side effects are extremely rare. Symptoms would include:

  • Tremors
  • Convulsions
  • Slow breathing, fatigue, and drowsiness
  • Shortness of breath, chest pain

Any of these symptoms requires immediate care. Call an ambulance and go to the nearest hospital emergency department.

How much phenol will I get?

The amount of medicine that you will receive depends on the degree of spasticity and muscle groups that are spastic. The usual dose is 2 to 3ml per site. Most individuals receive injections in one to four sites.

How is phenol therapy done?

The doctor and treatment team help the patient and family member or caregiver to identify goals before treatment begins. Next, small electrodes are attached with tape to the skin over the muscle and nerve areas that will be injected with phenol. The electrodes are attached to an electromyography (ee-lek-tromy-OG-rif-ee) machine. This machine does a procedure called an electromyogram (EMG). The EMG is used to be sure the needle is in the right place before phenol injection.

The physician uses tiny electric shock impulses to find the precise location of the nerve to be injected. These impulses may make your arm or leg move involuntarily (without your moving it on purpose). The medicine is injected around the nerve using a small needle attached to the machine. The physician may inject small amounts of phenol into several locations along the nerve or within several muscle or nerve groups to get the most benefit from the medicine.


A follow-up appointment will be made four to eight weeks after phenol therapy. At this appointment the doctor will check on the effects of the phenol therapy and will make further treatment recommendations if needed.

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