Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Birth control: Women taking birth control pills may need a lower dose of tizanidine to achieve a good effect. Birth control pills prevent tizanidine from leaving the body readily and may cause tizanidine to build up in the body leading to side effects.
Drowsiness/reduced alertness: This medication may cause drowsiness and severe dizziness. Do not drive, operate machinery, or perform other potentially hazardous tasks until you have determined how this medication affects you.
Heart rhythm: Tizanidine can cause changes to the normal rhythm of the heart, including an irregular heartbeat called QT prolongation. QT prolongation is a serious life-threatening condition that can cause fainting, seizures, and sudden death.
If you are at risk for heart rhythm problems (e.g., people with heart failure, angina, low potassium or magnesium levels), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and
effectiveness of this medication, and whether any special monitoring is needed.
Liver function: Tizanidine is removed from the body by the liver and may cause liver problems. If you have liver disease or decreased liver function, discuss with your doctor how this medication may affect your medical condition, how your medical
condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.
Low blood pressure: Symptoms of severe lowering of blood pressure, such as weakness or dizziness, particularly when rising suddenly from a sitting or lying position, may occur. People who are prone to low blood pressure (e.g., those taking diuretics)
should be cautious when using this medication. This effect may happen before the dose of medication is enough to reduce the muscle spasticity. Starting this medication at a very low dose and gradually increasing the daily dose helps to reduce the effect of
rapidly dropping blood pressure.
Mental health: Tizanidine can cause hallucinations (e.g., seeing or hearing things that are not really there). People with a history of mental health concerns, such as psychosis or schizophrenia are more likely to experience this effect. If you have
a history of mental health issues, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Stopping the medication: Stopping this medication suddenly can cause increased muscle spasms, an increase in blood pressure, or a rapid heart rate. Talk to your doctor before stopping this medication.
Pregnancy: Tizanidine has not been studied for use by pregnant women. In some animal studies, tizanidine caused birth defects and other pregnancy problems. This medication should not be used during pregnancy unless the benefits outweigh the risks.
If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: It is not known if tizanidine passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using tizanidine has not been established for children less than 18 years of age.
Seniors: Tizanidine is cleared from the body at a slower rate in older adults. This can result in an increase in the number and severity of side effects. The doctor will take this into consideration when determining the dose you should be taking.