Study of the Antiplatelet Effects of Ticagrelor vs. Clopidogrel in Hispanic Patients with Stable Coronary Artery Disease

There are 53 million Hispanics in the United States, representing approximately17 percent of the population. This number is expected to increase to 100 million by the year 2060.

Hispanics, like women, have been historically underrepresented in pharmacology studies. While the pharmacologic effects of many commonly prescribed medications on white males have been closely studied , clinically important variations in medication response among minority patients are often understudied and unknown.

“In this study, we wanted to better understand the antiplatelet effects of ticagrelor versus clopidogrel in Hispanic patients,” said Leonardo Clavijo, MD, cardiologist and assistant professor of medicine at USC School of Medicine, during a poster presentation at the 2013 American Heart Association Scientific Sessions, in Dallas, TX.

For the current study, 40 patients with heart disease who treat their condition with low-dose aspirin were enrolled and randomized to receive treatment, with 38 patients completing the study. Many of the patients also suffered from obesity. More than 50 percent of the cohort was diabetic and study participants’ average age was 65 years.

The study consisted of two treatment periods separated by a 10-14 day washout period. During each treatment period, patients received one of two possible treatments. Treatment A consisted of a 600 mg loading dose of clopidogrel followed by 75 mg daily for 7-9 days. Treatment B consisted of a loading dose of 180 mg of ticagrelor, followed by 90 mg twice daily. All patients received 75-100 mg daily of low-dose aspirin throughout the treatment.

The primary objective of the study was to compare the on-treatment platelet reactivity of ticagrelor versus clopidogrel at two hours after the loading dose of each treatment as measured by P2Y Reaction Units (PRU).

The secondary objective was to compare the on-treatment platelet reactivity of ticagrelor versus clopidogrel at 0.5 and 8 hours after loading dose; at 2 and 8 hours after treatment on day 7; and at the end of the dosing interval (12 hours after the last evening dose of ticagrelor and 24 hours after the last morning does of clopidogrel on day 8). The study also assessed the safety of ticagrelor by reported adverse events, physical examination, and vital signs.

At 30 minutes after the loading dose, on-treatment reactivity following administration of ticagrelor was 135 PRU (95% CI: 105-164 PRU) compared with 270 PRU (95% CI: 239-301 PRU) following administration of clopidogrel.

At 2 hours after the loading dose, on-treatment reactivity was 34 PRU and 201 PRU following administration of ticagrelor and clopidogrel, respectively.

At 8 hours after the last dose, on-treatment reactivity was 39 PRU and 179 PRU following administration of ticagrelor and clopidogrel, respectively.

The study authors concluded that treating Hispanic patients with stable CAD with daily low-dose aspirin plus ticagrelor provided lower levels of on-treatment platelet reactivity with a faster onset and greater extent of platelet inhibition, compared to treatment with aspirin plus clopidogrel.