There are many methods for the assessment of venotropic drugs. Clinical trials based on randomized comparison with placebo are essential. The different methodes used for the evaluation of the functional effects are chosen on the basis of their performance and pertinence for the study objectives. These include three aims which we feel are essential: increased venous tone, decreased capillary permeability and reversal of microcirculatory impairment. Calf plethysmography is highly adapted for the evaluation of venous tone. The mercury gauge works well, but the future will tell if air plethysmography is more adapted here. For capillary permeability, fluoresceine angioscopy is without a doubt the most sensitive and specific method. Unfortunately many laboratories do not have this equipment. If it is not available, the suction cup test or the Landis isotope test may be used although these tests have their limits. For impaired microcirculation, the most interesting test is the laser-Doppler; the results are well correlated with the severity of the chronic venous insufficiency and return to normal after treatment. TcPO2 and capillaroscopic measurements are less sensitive, but are useful in severe cases. Other investigations may be important in individual cases depending on the impact of the medication under study. Drug-induced serum fibrinolytic activity can be measured by the euglobulin lysis time. A haemorheologic effect can be assessed with routine assays (haematocrit, serum fibrinogen) and measured with tests of red cell deformability and erythrocyte agreggation capacity.
