Side Effects

Drug information provided by: Merative, Micromedex®

Along with their needed effects, thioxanthenes can sometimes cause serious side effects. Tardive dyskinesia (a movement disorder) may occur and may not go away after you stop using the medicine. Signs of tardive dyskinesia include fine, worm-like movements of the tongue, or other uncontrolled movements of the mouth, tongue, cheeks, jaw, or arms and legs. Other serious but rare side effects may also occur. Some of these side effects, including severe muscle stiffness, fever, unusual tiredness or weakness, fast heartbeat, difficult breathing, increased sweating, loss of bladder control, and seizures, may be the sign of a condition called neuroleptic malignant syndrome. You and your doctor should discuss the good this medicine will do as well as the risks of taking it.

Although not all of these side effects may occur, if they do occur they may need medical attention.

Stop taking this medicine and get emergency help immediately if any of the following effects occur:


  1. Convulsions (seizures)
  2. difficulty in breathing
  3. fast heartbeat
  4. high fever
  5. high or low (irregular) blood pressure
  6. increased sweating
  7. loss of bladder control
  8. muscle stiffness (severe)
  9. unusually pale skin
  10. unusual tiredness

Check with your doctor as soon as possible if any of the following side effects occur:

More common

  1. Difficulty in talking or swallowing
  2. inability to move eyes
  3. lip smacking or puckering
  4. loss of balance control
  5. mask-like face
  6. muscle spasms, especially of the neck and back
  7. puffing of cheeks
  8. rapid or worm-like movements of tongue
  9. restlessness or need to keep moving (severe)
  10. shuffling walk
  11. stiffness of arms and legs
  12. trembling and shaking of fingers and hands
  13. twisting movements of body
  14. uncontrolled chewing movements
  15. uncontrolled movements of the arms and legs

Less common

  1. Blurred vision or other eye problems
  2. difficult urination
  3. fainting
  4. skin discoloration
  5. skin rash


  1. Hot, dry skin or lack of sweating
  2. increased blinking or spasms of eyelid
  3. muscle weakness
  4. sore throat and fever
  5. uncontrolled twisting movements of neck, trunk, arms, or legs
  6. unusual bleeding or bruising
  7. unusual facial expressions or body positions
  8. yellow eyes or skin

Symptoms of overdose

  1. Difficulty in breathing (severe)
  2. dizziness (severe)
  3. drowsiness (severe)
  4. muscle trembling, jerking, stiffness, or uncontrolled movements (severe)
  5. small pupils
  6. unusual excitement
  7. unusual tiredness or weakness (severe)

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  1. Constipation
  2. decreased sweating
  3. dizziness, lightheadedness, or fainting
  4. drowsiness (mild)
  5. dryness of mouth
  6. increased appetite and weight
  7. increased sensitivity of skin to sunlight (skin rash, itching, redness or other discoloration of skin, or severe sunburn)
  8. stuffy nose

Less common

  1. Changes in menstrual period
  2. decreased sexual ability
  3. swelling of breasts (in males and females)
  4. unusual secretion of milk

After you stop taking this medicine your body may need time to adjust, especially if you took this medicine in high doses or for a long time. If you stop taking it too quickly, the following withdrawal effects may occur and should be reported to your doctor:

Although not all of the side effects listed above have been reported for all thioxanthenes, they have been reported for at least one of them. However, since these medicines are very similar, any of the above side effects may occur with any of them.

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.