Side Effects

Drug information provided by: Micromedex

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Serious side effects are very rare when dantrolene is taken for a short time, for example, when it is used for a few days before, during, or after surgery or anesthesia to prevent or treat malignant hyperthermia. However, serious side effects may occur, especially when the medicine is taken for a long time.

Check with your doctor immediately if any of the following side effects occur:

Less common

  1. Bloody or black, tarry stools
  2. bloody or dark urine
  3. bluish color changes in skin color
  4. changes in speech
  5. chest pain
  6. confusion
  7. constipation
  8. convulsions (seizures)
  9. decrease in frequency of urination
  10. decrease in urine volume
  11. difficult urination
  12. difficulty in moving
  13. difficulty in passing urine (dribbling)
  14. difficulty in swallowing
  15. fast, pounding, or irregular heartbeat or pulse
  16. increased frequency of urination
  17. increased urge to urinate during the night
  18. joint pain
  19. light-colored stools
  20. lightheadedness
  21. loss of bladder control
  22. mental depression
  23. muscle aching or cramping
  24. muscle pains or stiffness
  25. muscle spasm or jerking of all extremities
  26. nausea and vomiting
  27. pain in lower back
  28. pain or burning while urinating
  29. pain, tenderness, or changes in skin color
  30. painful urination
  31. severe stomach pain
  32. shortness of breath
  33. skin rash, hives, or itching
  34. slow or troubled breathing
  35. sudden decrease in amount of urine
  36. sudden loss of consciousness
  37. swelling of foot or leg
  38. swollen joints
  39. unusual tiredness or weakness
  40. upper right abdominal pain
  41. vomiting of blood or material that looks like coffee grounds
  42. waking to urinate at night
  43. yellow eyes or skin

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. Diarrhea
  2. dizziness
  3. drowsiness
  4. general feeling of discomfort or illness
  5. muscle weakness

Less common

  1. Abdominal or stomach cramps or discomfort
  2. abnormal hair growth
  3. acne-like rash
  4. blurred or double vision or any change in vision
  5. change in taste
  6. chills and fever
  7. disturbed color perception
  8. excessive tearing
  9. halos around lights
  10. headache
  11. itching skin
  12. loss of appetite
  13. night blindness
  14. overbright appearance of lights
  15. redness of skin
  16. seeing double
  17. skin rash, encrusted, scaly and oozing
  18. sleeplessness
  19. slurring of speech or other speech problems
  20. sudden decrease in amount of urine
  21. sweating
  22. trouble in sleeping
  23. tunnel vision
  24. unable to sleep
  25. unusual nervousness
  26. weight loss

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.