I take Zanaflex (tizanidine) or flexeril (have both) and just started necon 10/11. I read there could be interactions with zanaflex (tizanidine). Do I need to be concerned?

Yes, it is possible. Zanaflex (tizanidine) & Flexeril are muscle relaxants, while Necon 10/11 is an oral contraceptive.All the three medications are metabolized in the liver through cyp450. Necon is an inhibitor of 3a4 sub-enzyme, while Zanaflex (tizanidine) and Flexeril are not. Necon may increase the levels of Flexeril and zanaflex, (tizanidine) causing increased sedation, dizziness, impairment of fine motor movements, coordination and risk of fall.
Yes- Sedation/dizzy. If you use Zanaflex (tizanidine) chronically, know that the concentration of Zanaflex is increased when used with oral contraceptive and may result in increased sedation, fatigue/ low blood pressure (hypotensive issues- dizziness, fainting). You may want to use Flexeril (cyclobenzaprine hcl) instead but also watch out for drowsiness, fatigue, dizziness. Avoid alcohol and use caution when driving while on these drugs.