Can muscle relaxers be addicting?

Perhaps habituating. Most muscle relaxant medications have little addiction or habituation risk. However, Soma (carisoprodol) or carisoprodal does metabolize to "miltown", an older sedative that was prone to abuse and definitely habit forming. And people do vary sharply in their responses to these types of medicines. If you feel there is a problem stopping or altering a dose, discuss at length with your doctor.