What are some side effects of muscle relaxants?

Some muscle relaxants such as carisoprodol and metaxalone generally don't produce tolerance (the need for increasingly larger doses to obtain the same effect), but they may cause drowsiness and fatigue, which, in turn, can impair mental and physical functioning. Thus, avoid driving, operating heavy equipment, or performing other hazardous tasks while taking these medications. Muscle relaxants aren't recommended for people with liver or kidney disease or a history of drug dependency.