Short-term effects of
ridogrel, a combined
thromboxane synthase inhibitor and receptor antagonist, were investigated in 16 patients with uncomplicated
essential hypertension. After a 2-week placebo period without
antihypertensive medication, patients were admitted to the hospital overnight on two occasions 3 weeks apart. On each occasion, they received two doses of either placebo or
ridogrel (300 mg) 12 hours apart according to a double-blind crossover protocol. Renal and systemic
thromboxane A2 and
prostacyclin biosynthesis were investigated by measuring urinary excretion of
thromboxane B2, 6-oxo-prostaglandin F1 alpha, and their respective 2,3-dinor metabolites using gas chromatography/mass spectrometry. Responses of platelets to a
thromboxane A2 mimetic and to
adenosine diphosphate were studied turbidometrically. Blood pressure was measured automatically at 20-minute intervals.
Ridogrel reduced excretion of
2,3-dinor-thromboxane B2 and
thromboxane B2 compared with placebo (21 +/- 6 versus 279 +/- 28 and 14 +/- 4 versus 39 +/- 9 ng/g
creatinine, respectively; P < .0001 and P < .05). Excretion of 2,3-dinor-6-oxoprostaglandin F1 alpha and
6-oxoprostaglandin F1 alpha was increased by
ridogrel compared with placebo (184 +/- 20 versus 146 +/- 11 and 86 +/- 9 versus 58 +/- 6 ng/g
creatinine, respectively; P < .05).
Ridogrel selectively antagonized platelet aggregation to the
thromboxane mimetic (P < .0001). Blood pressure did not differ significantly between
ridogrel and placebo treatment periods. Thus, in patients with
essential hypertension, acute administration of
ridogrel reduces renal and extrarenal
thromboxane A2 biosynthesis, increases renal and extrarenal
prostacyclin biosynthesis, inhibits
thromboxane receptor-activated platelet aggregation, but has no effect on systemic arterial pressure.