Co‐Prescription of Strong CYP 1A2 Inhibitors and the Risk of Tizanidine‐Associated Hypotension: A Retrospective Cohort Study

• Published in: Clinical pharmacology and therapeutics 2019-03, Vol.105 (3), p.703-709
• Main Authors: Chaugai, Sandip, Dickson, Alyson L., Shuey, Megan M., Feng, QiPing, Barker, Katherine A., Wei, Wei‐Qi, Luther, James M., Stein, C. Michael, Chung, Cecilia P.
• Format: Article
• Language: English
• ISSN: 0009-9236; 1532-6535
• DOI: 10.1002/cpt.1233

Tizanidine, a widely used muscle relaxant that can lower blood pressure, is metabolized by the cytochrome P450 1A2 ( CYP 1A2). We studied 1,626 patients prescribed tizanidine and 5,012 prescribed cyclobenzaprine concurrently with a strong CYP 1A2 inhibitor. The primary outcome was severe hypotension, defined as systolic blood pressure ( SBP ) ≤ 70 mmHg during periods of drug co‐exposure. Severe hypotension occurred more often in the tizanidine group (2.03%; n  =   33) than the cyclobenzaprine group (1.28%; n  =   64); odds ratio ( OR ) = 1.60; P  =   0.029. This difference remained statistically significant after adjustment for a log‐transformed propensity score that included age, sex, race, Charlson's comorbidity index, and concurrent use of antihypertensive medications ( OR  = 1.57; P  =   0.049). A sensitivity analysis that defined hypotension as SBP