Available online on www.ijtpr.com International Journal of Toxicological and Pharmacological Research 2017; 9(2); 99-104 ISSN: 0975-5160 Research Article *Author for Correspondence: bustanji@ju.edu.jo Prevalence of Aspirin Resistance among Jordanian Patients with Cardiovascular Disease Eman Elayeh 1 , Mohammad Mohammad 1 , Mohammad Fararjeh 2 , Eman Abu-Rish, Islam Hamad 3 , Violet Kasabri, Amal Akour, Yasser Bustanji 1,4* 1 School of Pharmacy, The University of Jordan, Amman, Jordan 2 Al-Quods Medical Laboratory, Al-Zarqa, Jordan 3 Faculty of Health Sciences Department of Pharmacy, The American University of Madaba 4 Hamdi Mango Center for Scientific Research, The University of Jordan, Amman, Jordan Available Online: 1 st May, 2017 ABSTRACT Introduction: Despite the wide range of aspirin indications, there is a considerable amount of patients do not respond to aspirin, who also are referred to as aspirin non-responders or aspirin resistant patients. Aims and objectives: This study was carried out to prospectively evaluate the prevalence of aspirin resistance in Jordanian patients with cardiovascular disease and further clarify the clinical predictors of aspirin resistance. Materials and methods: Biochemical aspirin response was assessed based on the measurements of urinary11-dehydro thromboxane B 2 (11-dhTxB 2 ) levels using FDA approved diagnostic kit. Patients taking aspirin (75-325mg) for at least 7 days were prospectively enrolled from all stable cardiac patients presenting at Jordan University hospital outpatient clinics. Results: Eighty six (86) patients were enrolled in this study. Another twenty four healthy individuals were enrolled to function as a control group. The mean urinary levels of 11- dhTxB 2 /creatinine were significantly lower almost 3- times in patients in the primary and secondary aspirin prevention group compared with the control group (1567.58 vs. 4236.19 pg/mg, p-value <0.005). Thirty-one patients were found to be aspirin resistant with a prevalence of 36%. Conclusion: Our findings of aspirin resistance are particularly important given the large number of patients using this medication for prevention of atherothrombotic events. These results indicate that aspirin resistance should be diagnosed so that individuals with no response to aspirin can receive an alternative or an additional antiplatelet therapy. Keywords: Aspirin resistance, dehydrothromboxane B 2 , cardiovascular disease, Jordan. INTRODUCTION Cardiovascular diseases (CVD) are responsible for the majority of deaths in the developed countries 1,2 . Aspirin is recommended by different agencies for primary and secondary prevention of different cardiovascular diseases 3,4 . It exerts its effect by the inhibition of cyclooxygenase enzyme which is responsible for the conversion of arachidonic acid to prostaglandins (PG) and thromboxane A 2 (TxA 2 ) 3,4 . Despite the wide range of aspirin indications, there is a considerable amount of patients do not respond to aspirin, who also are referred to as aspirin non-responders. The term Aspirin resistance is used to describe different events including: i) the failure of aspirin to protect against thrombotic complications; ii) the inability of aspirin to result in prolonged bleeding time; iii) the failure of aspirin to inhibit TxA 2 production and iv) the inability of aspirin to prevent platelet function in vitro 5,6 . Aspirin resistance is defined as laboratory and clinical resistance 7 . Laboratory aspirin resistance can be defined as the failure of aspirin to inhibit the production of platelet TxA 2 or inhibit tests of platelet function that depend on platelet thromboxane production. However, clinical aspirin resistance is the failure of aspirin to protect the patient from an ischemic event despite regular intake of appropriate doses 7 . Different methods have been employed for the detection of aspirin resistance but none of them is considered a specific and sensitive test to be routinely recommended as a screening method to detect aspirin resistance in clinical practice 8 . On the other hand, urinary levels of 11- dehydrothromboxane B 2 (11-d HTxB 2 ) have been proved to coorrelate with cardiovascular mortlity in high risk patients treated with low dose aspirin 9 . and are directly dependent on aspirin's target COX-1 8,9 . 11-d HTxB2 levels also reflect in vivo thromboxane production 8 and are measured by a non-invasive method which is normalized with standard controls 10 . This study was carried out to prospectively evaluate the prevalence of aspirin resistance in Jordanian patients with cardiovascular disease using urinary 11-dHTxB 2 level measurement and further clarify the clinical predictors of aspirin resistance. MATERIALS AND METHODS Patients and controls