Tizanidine is known to cause low blood pressure. In some cases, it may cause low blood pressure that is so low that you could faint or pass out. The chances of fainting can be lowered if your doctor raises the dose of tizanidine very slowly. You may also have to be careful when you move from a sitting position to a standing position. In clinical trials, the most common side effects of tizanidine were dry mouth, sleepiness, dizziness and asthenia (defined as weakness, fatigue and/or tiredness).