Studies on the Effect of Long-Term Use of Low Dose Aspirin in Kawasaki Disease

The inhibitory action of long-term low dose aspirin (1–2 mg/kg/day for over 10 months) on the cyclooxygenase pathway in platelets and vascular endothe-lium was evaluated in 10 patients with Kawasaki disease. The results were compared with those obtained after taking aspirin at 5–10 mg/kg/day during the acute phase of the illness. Platelet aggregations induced by adenosinedi-phosphate (ADP), epinephrine and collagen were inhibited by aspirin doses of 1–2 and 5–10 mg/kg/day, when compared with those of controls (p < 0.05). Platelet synthesis of thromboxane B₂ (TXB₂) under doses of 1–2 and 5–10 mg/kg/day was 0.57 ± 0.07 and 0.72 ± 0.09 ng/ml platelet-rich plasma (PRP) /10⁵ platelets, respectively (p > 0.1). These values were significantly lower than those of the control group (22.88± 3.42 ng/ml PRP/10⁵ platelets) (p < 0.05). No differences were found in platelet aggregation and TXB₂ productivity between the two aspirin doses. Levels of 6 keto-prostaglandin F₁α (6k-PGF₁α) in platelet-poor plasma (PPP) did not differ significantly in these 3 sets of data. The results indicate that long-term administration of low dose aspirin (1–2 mg/kg/day) inhibits platelet aggregation by inhibiting synthesis of thromboxane A₂ (TXA₂), without interfering with prostacyclin production probably in the endothelium of blood vessels.