Amlodipine alters hemorheological parameters: Increased efficacy at the cost of edema?

BACKGROUND: Despite several decades of use of calcium channel blockers, the side effect of edema persists as a class effect, and its mechanism is unresolved. Amlodipine has effects on hemorheology (HR), and its hemodilutory property may partly contribute to its antihypertensive action. This aspect is not well studied, and the literature is sparse in this regard. OBJECTIVE: This experiment was planned to determine effect of a single-dose administration of amlodipine on HR parameters in normal human volunteers. METHODS AND RESULTS: Amlodipine (5 mg) or S (-) amlodipine (2.5 mg) was administered to 27 normal human volunteers. Whole-blood viscosity (WBV) at different shear rates, plasma viscosity (PV), red cell rigidity (RCR), red cell aggregation (RCA), hematocrit (Hct), plasma hemoglobin, along with plasma drug concentration were determined at time intervals, t = 0, 4, 8, 12, and 24 h. Statistically significant reductions were observed at tmax = 4 h in WBV at shear rates of 0.512 s-1 (p < 0.005), WBV at shear rates of 5.26 s-1 (p < 0.01), PV (p < 0.05), and Hct (p < 0.01). At t = 8 h, as drug concentration reduced, some of the changes persisted and later slowly decreased with the decreasing drug concentration till t = 24 h. Red blood cell-related parameters such as RCA and RCR remained unaltered. WBV values at all shear rates, when corrected for Hct = 0.45, did not show deviation from their original values at any time. CONCLUSIONS: Amlodipine causes a reduction in Hct and blood viscosity, along with hemodilution. These effects persist as long as the drug remains in plasma. Edema resulting from chronic dosing may be explained by the aforementioned effects. It is possible that antihypertensive action of the drug may be due to a combination of vasodilatation and an improvement in the HR properties.

Long-term assessment of efficacy and safety of L1, an oral iron chelator, in transfusion dependent thalassaemia: Indian trial.

From August 1989 to May 1991, 52 patients with transfusion dependent thalassaemia major received L1 (1,2-dimethyl-3- hydroxypyrid-4-one), the oral iron chelator, for a period of 3-21 months (mean +/- SD: 14.2 +/- 6.8). Mean (+/- SD) urinary iron excretion varied from 6.2 +/- 4.6 mg/d on 25 mg/kg/d of L1 to 42.3 +/- 37.1 mg/d on 100 mg/kg/d of L1. Mean (+/- SD) drop in S ferritin was 1465 +/- 990 micrograms/l after 5.0 +/- 0.8 months to 3641.2 +/- 2299.3 micrograms/l after 20.1 +/- 0.9 months of therapy. There was no evidence of neutropenia, thrombocytopenia, ear or eye toxicity. L1-related arthralgia, which was reversible on dose reduction or stoppage, was seen in 20 patients (38.5%), while minor gastrointestinal (GI) tract symptoms occurred in seven (3.5%) cases. We conclude that although L1 is an effective iron chelator, further studies are required to understand the mechanism of L1 related arthralgia and also to find a safer but effective dose on which incidence of L1 related arthralgia is minimal.