NEW YORK (Reuters Health) – In patients being treated for acute coronary syndromes (ACS), the loading dose of ticagrelor has a stronger inhibitory effect on platelets than does clopidogrel, and ticagrelor continues to have a superior effect during maintenance, according to a substudy of the PLATO trial.

PLATO showed that ticagrelor was better than clopidogrel in preventing ischemic events in patients with ACS, Dr. Robert F. Storey at the University of Sheffield, UK, and colleagues note in the October 26 issue of the Journal of the American College of Cardiology.

Participants were randomized to receive either clopidogrel, with a loading dose of 300-600 mg followed by 75 mg/d, or ticagrelor at 180 mg for a loading dose and 90 mg b.i.d. for maintenance.

The antiplatelet effects of maintenance therapy were studied in 69 patients after at least 28 days of treatment.

Platelet aggregation using ADP as agonist was measured by light transmittance aggregometry; mean readings were 44 units with clopidogrel versus 28 units with ticagrelor (p<0.001).

A platelet reactivity index of 50, as measured by the VASP assay, was documented more frequently in the clopidogrel group, according to the report. For example, just before a maintenance dose, the index was above the 50 threshold in 68% of clopidogrel patients compared with 9% of ticagrelor patients.