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Tizanidine, a widely used muscle relaxant that can lower blood pressure, is metabolized by the cytochrome P450 1A2 (CYP1A2). We studied 1,626 patients prescribed tizanidine and 5,012 prescribed cyclobenzaprine concurrently with a strong CYP1A2 inhibitor. The primary outcome was severe hypotension, defined as systolic blood pressure (SBP)≤70 mm Hg 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)]; 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<90 mm Hg also yielded higher rates of hypotension among patients prescribed tizanidine. In conclusion, CYP1A2 inhibition increases the risk of hypotensive episodes associated with the use of tizanidine in routine clinical practice. This article is protected by copyright. All rights reserved.
This article was published in the following journal.
Name: Clinical pharmacology and therapeutics
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Drugs and compounds which inhibit or antagonize the biosynthesis or actions of CYTOCHROME P-450 CYP1A2.
Drugs and compounds that induce the synthesis of CYTOCHROME P-450 CYP1A2.
The transfer of prescription drugs from legal to illegal distribution and marketing networks.
A cytochrome P-450 monooxygenase that can be induced by polycyclic aromatic xenobiotics in the liver of human and several animal species. This enzyme is of significant clinical interest due to the large number of drug interactions associated with its induction and its metabolism of THEOPHYLLINE. Caffeine is considered to be a model substrate for this enzyme. CYP1A2 activity can also be increased by environmental factors such as cigarette smoking, charbroiled meat, cruciferous vegetables, and a number of drugs including phenytoin, phenobarbital, and omeprazole.
Drugs that cannot be sold legally without a prescription.
Clinical Approvals Clinical Trials Drug Approvals Drug Delivery Drug Discovery Generics Drugs Prescription Drugs In the fields of medicine, biotechnology and pharmacology, drug discovery is the process by which drugs are dis...
Arthritis Fibromyalgia Gout Lupus Rheumatic Rheumatology is the medical specialty concerned with the diagnosis and management of disease involving joints, tendons, muscles, ligaments and associated structures (Oxford Medical Diction...