Why does ritalin (methylphenidate) cause my urethra to tighten and contract (have spasms) when it wears off?

Normal Physiology. Ritalin (methylphenidate) is what is called a sympathomyometic. Your bladder is constantly in ballance with stimulent and depressent hormones in your body (called the sympathetic and parasympathetic nervous systems). When the Ritalin wears off in your body, your bladder and urethra get confused due to the change in hormone levels. Try using a long acting form of Ritalin or an alternative drug.