What should I watch for?
Your condition will be monitored carefully while you are receiving this medicine.
You may get drowsy or dizzy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. Do not stand or sit up quickly, especially if you are an older patient. This reduces the risk of dizzy or fainting spells. Alcohol may interfere with the effect of this medicine. Avoid alcoholic drinks.
If you are taking another medicine that also causes drowsiness, you may have more side effects. Give your health care provider a list of all medicines you use. Your doctor will tell you how much medicine to take. Do not take more medicine than directed. Call emergency for help if you have problems breathing or unusual sleepiness.
This medicine can make you more sensitive to the sun. Keep out of the sun. If you cannot avoid being in the sun, wear protective clothing and use sunscreen. Do not use sun lamps or tanning beds/booths.
Common and Rare Side Effects
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:
Bloody or black, tarry stools
bloody or dark urine
bluish color changes in skin color
changes in speech
decrease in frequency of urination
decrease in urine volume
difficulty in moving
difficulty in passing urine (dribbling)
difficulty in swallowing
fast, pounding, or irregular heartbeat or pulse
increased frequency of urination
increased urge to urinate during the night
loss of bladder control
muscle aching or cramping
muscle pains or stiffness
muscle spasm or jerking of all extremities
pain in lower back
pain or burning while urinating
pain, tenderness, or changes in skin color
severe stomach pain
shortness of breath
slow or troubled breathing
sudden decrease in amount of urine
sudden loss of consciousness
swelling of foot or leg
unusual tiredness or weakness
upper right abdominal pain
vomiting of blood or material that looks like coffee grounds
waking to urinate at night
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:
general feeling of discomfort or illness
Abdominal or stomach cramps or discomfort
abnormal hair growth
blurred or double vision or any change in vision
change in taste
chills and fever
disturbed color perception
halos around lights
loss of appetite
overbright appearance of lights
redness of skin
skin rash, encrusted, scaly and oozing
slurring of speech or other speech problems
sudden decrease in amount of urine
trouble in sleeping
unable to sleep
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.