Potential Synergism of Green Tea and Aspirin as a Possible Cause of Bleeding in a Diabetic

A 58 year old lady with Metabolic Syndrome of 10 years duration presented with post-menopausal PV bleeding, haematuria, occasional epistaxis and ecchymoses. Prescribed medication which had remained unchanged for the preceding two years included daily doses (mgms) of Aspirin (150), Atenelol (50), Metformin (500 × 3), Bendroflumethiazide (2.5), Losartan (50) and Simvastatin (20). Intravenous urogram, cystoscopy, cytological examination of urine sediment, hysteroscopy, a cervical scan and endometrial biopsies showed neither evidence of overt pathology nor any physiological indication for the cause of haematuria or PV bleeding. Tests for urinary infection were negative. Apart from the raised blood glucose (9.1: NR 3.3 – 6.0 mmol/L), the biochemistry profile including liver enzymes, coagulation profile and blood count were normal (Platelets = 265 × 10⁹/L). Bleeding episodes were observed after commencement of a daily intake of 7–8 cups of green tea for a period of six months. Green tea intake was self-instigated in response to reported amelioration of risk factors associated with Metabolic Syndrome (reduction in LDL cholesterol and serum triglyceride levels; elevation of protective HDL; potent antioxidant activity; ACE inhibition and promotion of glucose metabolism). Hot water extract of green tea specifically inhibits platelet adhesion and lowers sub-maximal platelet aggregation and prolongs the lag time in a dose-dependent manner. Previous fractionation studies of these hot water extracts, has revealed that the tea catechins (tannins) actively inhibit thromboxane A2 production and that ester-type catechins are more effective than free-type catechins. One of the ester-type catechins, epigallocatechin gallate (EGCG), suppresses thrombin and collagen-induced platelet aggregation completely at a concentration of 0.2 mg/ml. EGCG also inhibits aggregation by a mechanism which differs from that of aspirin by inhibiting platelet activating factor (PAF). The IC50 values of EGCG and aspirin indicate that their potencies are comparable. Bleeding symptoms ceased two weeks after the patient stopped drinking green tea. Our assumption of the causal effect of green tea on anomalous bleeding in this patient needs to be confirmed by structured platelet function tests in both aspirinised and non-aspirinised patients. Since inhibition of cyclo-oxygenase is an additional anti-thrombotic property of aspirin which differs from that of green tea, diabetic patients taking prophylactic low-dose aspirin should continue to do so and potentially beneficial ingestion of green tea should not be considered without consultation with an appropriate health professional in view of its synergistic potential on the effect of aspirin and the associated haemorrhagic risks.