Large between-physician differences exist in the magnitude of the white-coat effect that cannot be explained by patient characteristics. Physicians should therefore not make any decisions based on blood pressure measured manually during a first encounter.
1 The kinetics of captopril plasma levels and of the drug-induced plasma converting enzyme activity (PCEA), plasma renin activity (PRA) and diastolic blood pressure (DBP) modifications were studied over 24 h after oral administration of captopril, 1 mg/kg, to ten hypertensive patients. 3 The onset of PCEA inhibition and of DBP decrease closely followed the rise of captopril's plasma levels, while that of PRA increase was delayed. In contrast, while captopril rapidly disappeared from plasma, its biological and antihypertensive effects were long-lasting. 4 The lack of correlation between the relative bioavailability of captopril and the induced reduction in DBP (evaluated by the corresponding AUCs) suggests that free unchanged captopril plasma monitoring is not an adequate indicator of hypertensive patients' potential responsiveness to captopril's blood pressure lowering effects.
Fifteen patients with hypertension due to phaeochromocytoma and 35 controls with essential hypertension were studied to assess the diagnostic value of urinary and plasma biochemical determinations in phaeochromocytoma. In every case of phaeochromocytoma the urinary concentration of vanillylmandelate, metanephrines, or adrenaline plus noradrenaline was diagnostic of the disease irrespective of whether the patient was normotensive or hypertensive at the time. Plasma determinations of adrenaline and noradrenaline, however, gave falsely negative results on three occasions.These findings suggest that urinary biochemical deter-
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