Pharmacologic Aspects of a Phlebotropic Drug in CVI-Associated Edema

Albert-Adrien Ramelet, MD

LAUSANNE, SWITZERLAND

ABSTRACT

Several phlebotropic drugs, or edema-protecting drugs, are available, the most important of which are found in the γ-benzopyrone family (). γ-Benzopyrones can be plant extracts, semisynthetic preparations, or synthetic preparations. This family is divided into two different groups: and , and flavanes (). The flavone group contains various types of molecule and includes . Here we discuss the pharmacologic aspects in edema associated with chronic venous insufficiency (CVI) of one of the reference phlebotropic drugs, micronized purified fraction (MPFF*), a semisynthetic preparation from the diosmin group, which represents the latest improvement in flavonoid formulation. Before we detail the pharmacologic aspects, a brief summary of the pathophysiology of edema in CVI is necessary. Several factors are implicated: the veins, which create the conditions favorable to edema; the microcir- culation, which is the site of fluid transfer into the interstitial tissue; and the lymphatics, which have a limited possibility to reduce edema. Major discoveries are currently being made in CVI and the microcirculation. Results of studies show that MPFF decreases capillary permeability and increases capillary resistance, which could partly be explained by inhibition of leukocyte activation, migration, and adhesion. This inhibition is linked to a significant decrease in plasma levels of endothelial adhesion molecules (VCAM-1 and ICAM-1) after MPFF treatment. Thus, the CVI-induced damage to the microcirculation is

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Proceedings from the symposium, &dquo;Edema in Chronic Venous Insufficiency: Pathophysiology, Assessment and Treatment,&dquo; European Congress of the Union Internationale de Phl6bologie, Bremen, Germany, September 27, 1999. ©2000 Westminster Publications, Inc., 708 Glen Cove Avenue, Glen Head, NY 11545, U.S.A.

19 (Abstract continued) counteracted by MPFF. The lymphatic system is also improved by MPFF treatment. The lymphagogue activity of MPFF has been demonstrated in experimental animal models and confirmed by microlymphographic measurement in patients suffering from severe CVI. The pharmacologic activity of MPFF in lymphedema was observed in a study using an animal model of acute lymphedema and in a study in patients with upper limb lymphedema secondary to breast cancer treatment. All these findings point to the impor- tance of acting on each factor involved in the formation and maintenance of edema. This pharmacologic activity is indeed reflected by the clinical efficacy on edema observed during treatment with MPFF.

*Daflon 500 mg, Alvenor, Ardium, Arvenum, Capiven, Detralex, Variton, Venitol.

Introduction Before we analyze the mode of action of MPFF in CVI-associated we should is of value in edema, briefly Pharmacologic therapy major phle- recall the of edema. Several fac- in edema associated pathophysiology bology, especially treating tors are involved in the formation of edema. First, with chronic venous insuficiency (CVI). The drugs of course, is venous hypertension, which is a con- used are called or phlebotropic drugs edema-pro- sequence of venous reflux and/or the well-known tecting agents, and several families of drug exist, risk factors of venous disease, such as prolonged such as and These benzopyrones . may standing position, heat, etc. Venous hypertension be plant extracts or synthetic substances. The in the venous trunks is automatically transmitted most important family is that of the benzopy- to the venules and capillaries, for there is no post- rones, which can be divided into two a- groups: the of venous coumarin capillary sphincter limiting impact benzopyrones including derivatives, on the In the microcir- which are used as oral and hypertension capillaries. anticoagulants; y-ben- culation, which is the site of fluid exchange with or flavonoids. Flavonoids can be fur- zopyrones the interstitial tissue, the anomalies observed in ther divided into two types of molecule:l~2 the case of venous disease/venous hypertension are increased and de- ~ and derivatives capillary permeability flavones, flavonols, (diosmin, creased resistance associated with a , rutin, etc); capillary local inflammatory process characterized by ~ flavanes, flavanones, and derivatives (hes- leukocyte activation, adhesion, and migration. In peridin, pycnogenol, etc). the short term, this local inflammatory reaction leads to tissue damage. As a consequence, these This presentation is devoted to micronized puri- pathological conditions lead to an increase in fied flavonoid fraction (MPFF), a semisynthetic fluid outflow into the surrounding tissues. At the micronized preparation of the y-benzopyrone early stages of the disease, this can be compen- family, which represents the latest improvement sated for by the lymphatic system, and no edema in flavonoid formulations. MPFF has improved occurs. However, the lymphatic function has a pharmacologic properties due to a micronized limited capacity for compensation. If chronic formula that increases bioavailability3 and thus venous disease persists and worsens, the lym- has greater therapeutic efficacy than nonmi- phatic system becomes overloaded and is no cronized diosmin.4 MPFF provides an excellent longer able to handle the excess fluid. At this opportunity to discuss all the pharmacologic stage of the disease, edema appears and is the mechanisms by which edema may be reduced result of an imbalance between inflow of intersti- with a phlebotropic drug. tial fluid and lymphatic drainage.

20 > Mode of Action of MPFF in caused an increase in the number of fluorescent CVI-Associated Edema vascular leakage sites in the postcapillary venules. The number of leaky sites per square centimeter edema means all the Fighting counteracting was UV mechanisms described above and in this quantified by light microscopy. Compared regard with vehicle, MPFF significantly inhibited the the mode of action of MPFF is perfectly suited to effect on the macromolecular permeability of his- the pathophysiology of this condition. tamine (343.5 ±22.3 vs 207.5 ±32.0; p<0.01), bradykinin (342.2 ±19.0 vs 206.2 ±21.6; Venous Tone p<0.01), and LTB4 (353.3 ±27.5 vs 242.7 ±33.6; p<0.05). These data demonstrate a protective MPFF has a demonstrated on venous tone. impact effect of MPFF of macromolecules has been observed in several against leakage This mechanism dif- after application of permeability-increasing sub- ferent studies: in vitro using the isolated venous stances to the cheek pouch microvasculature. segments,5,6 and in vivo using strain gauge Recently some experimental models have in CVI a plethysmography patients.7 Recently, been used to further study the mechanism of new method calculation of the elastic involving MPFF in the microcirculation. In one of these modulus (K) with air plethysmography confirmed trials, a dorsal skin-fold chamber preparation of the in venous tone after MPFF treat- improvement hamsters was used.l2 Animals received MPFF, or ment.8This controlled study involved 25 women an equivalent volume of the vehicle, by gavage with abnormal venous elasticity/venous tone, for 8 days. A 4-hour period of tourniquet ischemia divided into two groups: one group treated with was induced and the leakage of the macromole- MPFF (1,000 for 4 weeks, and the other mg/day) cule FITC-dextran (150 kd) was analyzed during a control group receiving no treatment. Two mea- reperfusion by intravital fluorescence microscopy. surements were made with air plethysmography Ischemia reperfusion injury was elicited by sig- (APG): one at the beginning of the study and a nificant macromolecular leakage from postcapil- second 4 weeks later. All measurements were per- lary venules in vehicle-treated animals. In the formed at constant temperature and at the same MPFF-treated group, the postischemic leakage was time of the The elastic modulus was day. (K) totally inhibited (p < 0.05) . These results indicate determined from the curve. The pressure-volume that MPFF of macromolecules results showed that the elastic modulus (K) in the prevents leakage from postcapillary venules. It was hypothesized control group remained the same at the end of that this effect may be linked to an inhibitory the study (p > 0.1), while in the MPFF group, action on the migration of activated leukocytes. venous tone was reinforced as demonstrated by This hypothesis was confirmed in another study 13 a increase in K (p<0.02). significant that focused on postischemic leukocyte/endothe- lial cell interactions and microvascular barrier dys- Microcirculation function in skeletal muscle in rats. In this trial performed in rat cremaster muscles, MPFF was The microcirculation is a valuable research field shown to attenuate the postischemic increases in in CVI, and in this context many studies with leukocyte rolling, adhesion, and migration. This MPFF have been published.9-15 The pharmacody- was associated with a decrease in venular protein namic activity of MPFF on the microcirculation leakage (p<0.05). and, more particularly, capillary filtration, was To assess the protective effect of MPFF, an studied in hamster cheek pouch preparation.9 experimental model of venular occlusion/reper- MPFF (20 mg/kg/day) was administered orally fusion in the rat mesentery was designed.14 The to the male hamsters for 10 days. The effect of degree of leukocyte/endothelium interaction and MPFF on increased microvascular permeability the extent of parenchymal cell death were deter- induced by histamine, bradykinin, and leuko- mined. The results of this study demonstrated that triene B4 (LTB4) was investigated by using intrav- when MPFF was administered for 7 consecutive ital microscopy. A fluorescent macromolecular days by gavage, it significantly reduced the conse- tracer (fluorescent isothiocyanate-labeled dextran quences of 1-hour venular occlusion: parenchymal 150 [FITC-dextran]) was given intravenously cell death, rolling of leukocytes, leukocyte adhe- after the cheek pouch preparation. Histamine, sion, and migration across the venous wall were bradykinin, and LTB4 were applied topically and all significantly decreased (p < 0.05) .

21 The first clinical research with MPFF in this was performed qualitatively and quantitatively. field was undertaken in 20 patients suffering from The results showed that MPFF decreased the chronic venous disease, stages C2 to C4 and C5 weight of the thighs, the concentration of protein (with a healed ulcer for at least 4 weeks) in tissue, and the number of fibroblasts, signifi- according to the CEAP classification. 15 All patients cantly and in a dose-dependent manner underwent venous duplex examination and pho- (p < 0.002 for a high MPFF dose, and p < 0.02 for toplethysmography to establish the precise diag- a low MPFF dose). Moreover, the reduced tran- nosis of venous disease. Plasma markers of scutaneous oxygen pressures in lymphedema endothelial (E-selectin, P-selectin, vascular cell were largely restored toward normal in both adhesion molecule [VCAM-1], intercellular adhe- MPFF groups. sion molecule [ICAM-1], and von Willebrand The dose-dependent effect of MPFF on lymph factor) and leukocyte activation (lactoferrin) drainage was also demonstrated in a study mea- were measured by ELISA tests before and after a suring the lymph flow. 17 This lymphagogue effect 60-day treatment with MPFF. Blood samples were of MPFF was confirmed in unanesthetized sheep taken from the long saphenous vein at the ankle before and after 5 days of MPFF administration. 18 before and after 30 minutes standing, which In this study, MPFF significantly increased the raises the venous pressure in the superficial veins lymph flow (MPFF-treated group versus control of the leg to between 70 and 80 mm Hg. After group: p < 0.001 ) . These results show the direct VCAM-1 and ICAM-1 levels treatment, plasma stimulatory effect of MPFF on lymphatic contrac- were reduced in significantly following therapy tility and on lymphatic flow, with, as a result, all patients. Lactoferrin and von Willebrand factor increased lymph drainage. levels were significantly reduced following A clinical confirmation of these experimental in a of with skin therapy subgroup patients data came from a study using microlymphog- changes. The significant decrease observed in raphy in CVI patients. 19 The microlymphographic VCAM-1 and ICAM-1 plasma levels as a conse- (diameter of and of MPFF is of in parameters lymphatic capillaries quence therapy major importance number of functional were the of the mode of action of the lymphatic capillaries) comprehension assessed in 24 with CVI because of the role of these adhesion patients third-stage drug, key before and after 28 days of treatment with MPFF molecules in the endothelial interaction with neu- (1 g/day), and 14 days after treatment was trophils, monocytes, and lymphocytes. The The pressure that some of these molecules are stopped. intralymphatic capillary finding specifi- was measured the Servo Pressure lowered in with skin indi- by Nulling cally patients changes The results show that the number of cates that MPFF or some of System. may improve prevent functional the skin induced chronic venous dis- lymphatic capillaries significantly damage by increased between DO and D28 and ease and fight the microcirculation-damaging (p=0.001) was at D42. The diameter of processes. unchanged lym- phatic capillaries and the intralymphatic pressure were significantly decreased at the end of the Lymphatic System treatment and increased after treatment was This confirms the beneficial Fighting edema does not simply involve rein- stopped (p=0.001). effect of MPFF the forcing venous tone and protecting the microcir- lymphatic by increasing culation. The third &dquo;actor&dquo; in CVI-associated microlymphatic density and improving microlym- edema, the lymphatic system, also plays a deci- phatic drainage. sive role. Pharmacologic data have confirmed the In an experimental study performed with activity of MPFF on lymph drainage. These exper- MPFF, randomized groups of rats were given imental results have since been confirmed by var- acute lymphostasis of the leg.16 Two groups of ious clinical studies performed in patients with animals received MPFF, at doses of 20 and 100 edema and lymphedema. One of these studies mg/kg/day. The control group received the was performed with patients suffering from upper vehicle. Several parameters were measured: limb lymphedema secondary to breast cancer weight of the thighs, thickness and total water treatment.20 Over 6 months of MPFF therapy content of the subcutaneous tissue, and transcu- (1,000 mg/day), lymphedema progressively taneous oxygen pressure. Electron microscopy reduced. ,

22 Conclusion ious studies performed in patients suffering from edema2l or These results The of MPFF has been lymphedema.20 suggest pharmacologic activity that the mode of action of MPFF suits in and clin- perfectly demonstrated many pharmacologic the pathophysiology of edema. ical trials studying the various mechanisms responsible for edema formation and persistence: decreased venous tone, microcirculation-dam- Albert-Adrien MD aging processes, capillary hyperpermeability, and Ramelet, overloading of the lymphatic system. MPFF has 2, place Benjamin-Constant been shown to improve each of these mecha- 1003 Lausanne nisms. This has been confirmed clinically in var- Switzerland

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