Tizanidine is an alpha2 agonist with central action whose myorelaxant effects are often used off-label against primary backpain in clinical practice. It is mainly metabolized by the liver. The concomitant use of CYP1A2 inhibitor drugs increases the plasmatic concentration and thus can cause serious adverse effects. Severe hypotension is the most memorable example. Its narrow therapeutic range and the interindividual different sensitivity to the molecule justify using it wisely. A clinical case is reported as illustration.