Comparative studies of drotaverine-acephyllinate (Depogen) and pentoxifylline (Trental)

THROMBOSIS RESEARCH 66; 693-706,1992 0049-3848/92 $5.00 + .OOPrinted in the USA. Copyright (c) 1992 Pergamon Press Ltd. All rights reserved.

COMPARATIVE STUDIESOF

DROTAVERINE AND PENTOXIFYLLINE

8.

Sarkadil,

Z. Kapui, P. Szentmiklosi,

I.

- ACEPHYLLINATE (TRENTAL)

Hermecz, L. Tardos

(DEPOGEN)

and Gy. Blasko’

Research Centre of Pharmaceutical and Chemical Works CHINOIN, 1325. Budapest, P.O.B. 110, lNationa1 Institute of Haematology and Blood Transfusion, Budapest and *First Department of Medicine, Tetenyi Teaching Hospital, Budapest, Hungary

(This paper was received 20/9 1990; sent for revision 5/12 1990; returned 16/4 1992; Accepted in revised form 29/4 1992 by Editor Markwardt)

ABSTRACT

Pentoxifylline is an orally active agent for the treatment of peripherial and cerebral vascular diseases. Pentoxifylline increases the deformability of red blood cells in vitro, reduces blood viscosity and decreases platelet aggregation and thrombus formation. Oepogen has shown antiaggregatory effect both in vitro and in ex vivo. The was about 3-5 times weaker than inhibitory effect of Pentoxifylline that of Oepogen. IC50=900 ug/ml for Oepogen and 3600/ug/ml for rich plasma. Oepogen has shown ex Pentoxifylline on human pi atelet vivo antiaggregatory effect on anaesthetised rabbits, I050=7 mg/kg in and 1050=300 mg/kg in case of orally case of iv. administration, compound inhibit the release of platelet administration. Both precoagulation factor, but the effect of Pentoxifylline was slighter.

INTRODUCTION agent for the Trental - Pentoxify lline (P> is an orally active cerebrovascular disease and a treatment of peripheral vascu lar diseases, number of other conditions involving a defective regional microcirculation. The primary mechanism by which it increases blood flow appears to be related in haemorrheological characteristics such as to an overall improvement deformability, blood viscosity, platelet aggregation and erythrocyte (RBC) plasma fibrinogen concentration (1,2,12,13). Pentoxifylline produced a marked decrease in platelet adhesion and aggregation to vessel walls in experimental animals (27) and in patients with peripheral vascular disorders (2,5,19) as well as cerebrovascular disorders (7,121. Key

Words:

acephyll.inate

platelet aggregation, - Oepogen

Trental 693

-

Pentoxifylline,

Orotaverine

-

PENTOXIFYLLINE

694

AND DERIVATIVES

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The in vitro filtrability of erythrocytes is significantly increased by Pentoxifylline, especially in case of a considerably decreased filtrability some damages (such as ATP depletion or osmotic shrinkage) due to (10,16,17). Drotaverine-acephyllinate Our compound, (6,7,3’,4’-tetraethoxy-l-benzyl-3,4-dihydro-isoquinoline was synthesized by Szentmiklosi and Meszaros (21).

Fig 1. Chemical structure

DepogenR (ORA) (fig 1) xanthine-7-acetate)

of Depogen

drug having more favourable pharmacological Depogen is a potential properties than the other salts of Drotaverine (9,20,22,24,29). Preclinical investigations showed a considerably decreased vascular and clinical resistance in the extremities, obviously due to its powerful peripheral vasodilator and spasmolytic effects (20). In the present experiments Pentoxifylline and Oepogen were compared their effects on the filtrability of human REX, on antiaggregatory regarding activity of human and rabbit platelets, ex vivo antiaggregatory activity in rabbits, on availability of platelet factor 3 and antiaggregatory activity on human leukocytes. MATERIALS Measurement of erythrocyte

AND METHODS

filtrability

The method described by Teitel (25) was applied to study the in vitro filtrability of erythrocytes. The filtration rate of concentrated red cell suspension was measured by using filter paper manufactured by Nucleopore Corporation, (type: SN 150413), syze of pores : 5 /uM. The human erythrocyte suspension ( about 40% hematocrit ) was incubated for 30 minutes at 37’C in a CPD preserving solution containing the test drugs on the indicated concentrations. Subsequently, the erythrocytes were centrifuged and the concentrated precipitate was filtered. The hemoglobin concentration of the filtered samples was determined in each case and it was used for making corrections for the slight deviations of the red cell concentrations in the samples. The filtration rate was given in the dimension of millilitres (ml) of filtered erythrocytes per minute. The calculated

time required (TO.5) and

for used

the filtration to characterize

of half of the red cells was the change in filtrability.

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According to the latest data in the literature, plasticity of the red cell membrane can be characterized adequately by the applied method, compared with other test as filtration through nucleopore membrane, methods such computerized deformability tests, etc. (26). Fresh normal RBC fresh RBC shrunken in hyperosmotic solution and RBC stored for 30 days at +i°C in a GPO blood-preserving solution were used in the experiments. Osmotic shrinking was elicited by the addition of a 1.6 mM NaCl solution, one from the originally producing a 11.5 times more concentrated isoosmotic solution. The filtrability of red cells was significantly decreased by this treatment and a similar decrease of filtrability occured after storing for 30 days. Platelet Measurement

of rabbit

platelet

aggregation:

In vitro

studies

aggregation

Platelet rich plasma (PRP) of rabbits of both sexes weighing 2 to 4 kg was used for the measurement, prepared in the following way. The animals were anaesthetized by 30 mg/kg body weight pentobarbital. Blood was drawn by heart puncture collected in 1:9 ratio in a plastic tube containing 3.8% sodiumcitrate solution, and centrifuged at BOO rpm (500 g) for 10 min. The supernatant PRP was drawn off with a plastic pipette. Platelet poor plasma (PPP) was obtained from the blood by centrifuging (4OOOg) for 5 minutes. PRP was diluted to the concentration of 250 000 //ul with 0.1 M Tris-HCl buffer of 7.5 pH containing 0.9% NaCl and 3mM CaC12. Platelet aggregation was measured according to Born’s method (3) with dual-channel Chrono-log type aggregometer . Aggregation was measured in test tubes of 0.5 ml by stirring at constant rate (1200 rpm) at 37’C. The measurements were started by addition of the following aggregatory agents: AOP (20 /uM/l) , Arachidonic Acid (528 /uM/l), Bovine Collagen lO/ug/ml and A23187 Ca ionophore (10 /uM/l). The change of light transmission was registered for 3 minutes. Measurement

of human platelet

Plasma centrifuging centrifuging

In the

aggregation

was mixed from the venous at 1500 rpm for 4 minutes at 4000 rpm for 10 minutes.

blood (PRP).

of 4 healthy volunteers by PPP was obtained by further

The platelet count of the obtained blood was adjusted to the following we proceeded as specified above. Aggregation addition of Ix~O-~ M/l AOP.

Platelet

aggregation:

ex vivo

300 000 tr//ul. was induced by

studies

and femals weighing 2 to 4 kg were anaesthetised with 30 Rabbits, males The trachea was prepared, the animals took breath mg/kg pentobarbital iv. cannula. The jugular vein was prepared to spontaneously through a tracheal In other experiments the compounds were inject the antiaggregatory agents. suspension. administered intragastrically in 1 ml 0,5 % carboxymethylcellulose 10 ml blood samples were drawn before and after 60 minutes of the administration of the drug.

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as described for the measurement of in we proceeded In th 8 following M/l ADP induced aggregation was compared before and after vitro . loThe results were expressed in % of the pretreatment treatment of drugs. values. Measurement

of human leukocyte washed leukocyte obtained from

The preparation Transfusion.

aggregation: suspension the National

was prepared Institute for

from the Hematology

leukocyte and Blood

was sedimented for 1 hour at +4’C. A great part of the supernatant It In the remaining, appr. 50 ml the sedimented red blood cells was discarded. and white blood cells were resuspended and distributed into plastic centrifuge tubes. Some of the remaining red blood cells were lysed with a hypotonic (8 ml suspension + 76 ml distilled water) for 25 sec., then isotonia solution by the addition of 4 ml 18% NaCl solution. White blood cells was readjusted were sedimented by centrifuging at 600 rpm for 15 minutes at 20°C. The supernatant was discarded and the white blood cells were suspended in 1 ml HES GmbH) . The suspension was diluted with HES and solution (Freseneus physiological saline in 1:l ratio until the adequate leukocyte count was reached. Viability of the leukocytes was determined by Trypan blue staining., The viability of the leukocyte suspension used was 80 to 85% in average. The polimorphonuclear (PMN) cell content of the leukocyte suspension used was 80% to 85% as shown by GIEMSA staining its platelet content being 2%. This platelet count did not interfere with the meas rement of aggregation. A suspension with the leukocyte count of 34x10 Lf/ml was used for the measurements. The measurements were performed in a dual-channel Chrono-log type aggregometer . To adjust the aggregometer, a part of the leukocyte poor suspension was diluted in physiological saline 1 to 100. The transmission obtained for this leukocyte poor suspension was considered as 100% aggregation. Aggregation was induced by arachidonic acid (1.2 x 10m3 M/l) and it induced 70 to 80% aggregation. The principle of our method corresponds to Born’s platelet aggregation measurement. The test

of platelet

factor

3 (PF 3) availability

PRP was prepared as described above in Chapter 2.1. The PF 3 availability was determined by the Stypven clotting time test according to Spaet ,and Cintron (18), which is based on activation of factors X and V by Russel s viper venom (RVV). 0.550 ml PRP was preincubated with various test drug concentrations. Collagen at a final concentration of 4 /ug/ml was added under continuous stirring at 37 OC. 0.1 ml plasma aliquots were transferred into standard coagulometer tubes (Coagulometer KC 1, Heinrich Amelung Co., WGermany) containing 0.1 ml CaC12 (stock solution = 25 mM/l) and 0.001 ml RVV (stock solution 5 /us/ml > . Clotting times were recorded and values from duplicates were calculated. ??

Results Haemorrheoloqical

filters

Fresh, of

effects normal human much smaller

red blood cells (RBC) rapidly penetrate through pore-size than their diameter. The mean filtration

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697

time was found to be between 5-8 minutes, showing a great individual variability. In our experiments both Pentoxifylline and Depogen significantly decreased the half-time of filtrability, thus showing an improvement in the filtrability of normal erythrocytes, too. This effect, however, was of minor degree (the decrease of TO 5 value being between 20-30%), therefore it could not be easily applied for the analysis of the dose-response curves of the test substances. That is why in vitro damaged - osmotically shrunken and for 30 days stored - erythrocytes were used for the detailed analysis. The effect of Pentoxifylline and Oepogen on freshly drawn, osmotically shrunken human red blood cells is demonstrated in Figure 2. The filtrability of both the Pentoxifylline and Depogen treated erythrocytes is significantly increased, i . e . the TO.5 value characteristic of filtrability is decreased. The maximum effects of the drugs are quite similar, however, the concentration of Oepogen eliciting the half maximum effect is significantly smaller than that of Pentoxifylline. Depogen elicits similar effect to Pentoxifylline in a 5-10 times smaller concentration. P Y.

DRA

%

Ko.5 Z5.M

170,~=

0.5 - I/JM

T,

/off ’

100-t

7

J.i.

I I \

0” E B

\ \

0

$4 c f 50r.4 E tn

Figure

2.

\T i\ ‘,T

p. =-T_____+? .I. i

Dose response curves for fresh human RBC filtrability. experiments. Means 2 SEM

Pentoxifylline Each points

and Oepogen on shrunken represent 4-8 separate

No further increase in filtrability could be achieved by concentrations of either drugs. This effect of Pentoxifylline by the bell-shaped curve represents the change in filtrability, high concentrations being less effective than the optimum dose 1984). Our results indicate that Oepogen has a similar optimum lower concentrations than Pentoxifylline. The effect of stored for 30 days similar to respect both 2) 7 regarding concentration range.

and Pentoxifylline is demonstrated those obtained with the concentration

increasing the characterized i.e. low and (Ambrus et al. range, but at

Depogen on the filtrability of in Figure 3. The results are in osmotically shrunken red cells dependence and the optimum

(REX) every (Fig. of the

PENTOXIFYLLINE

698

Vol. 66, No. 6

AND DERIVATIVES

DRA K0.5 z o.s-l/M

T .’ .‘J.

I

0

1

I

10

30

20

40

-

80

mg/l.

Figure

0

5

10

40

my/i

Dose response curves for Pentoxifylline and Oepogen on human RBC stored for 30 days. Each pooints represents 4 - 8 filtrability separate experiments. Means L SEM

3.

a summary of the results obtained with Pentoxifylline Table 1 presents (P), Oepogen (DRA) and its components, Drotaverine (OR) and xanthine-7-acetate The maximal effects of Pentoxifylline, Oepogen and on the filtrability. similar in both the osmotically shrunken erythrocytes Drotaverine are quite and those stored for 30 days. Table 1 The effect

of Pentoxifylline,%otaverine, Depogen and - 7 acetate on filtrability of human erythrocytes

Xanthine

Osmotically shrunken erythrocytes Treatment

Pentoxifylline

Minimum TO as % of the contra *? value

Clepogen

Drotaverine Xanthine-7-acetate + Drug concentrations

36 37 35 76

+ + -+ 2

5 8 7 10

eliciting

KO 5+

/,uM/ 5 0.5 - 1 2 - 3 10

Erythrocytes

for

Minimum TO

stored

30 days

as % of

the contra *? value 33 t 11 32 2 5 36 t 8 64 2 12

K0.5+

//uM/ 5-7 0.5 - 1 3 - 5 10

half-maximum effects

This effect is significant because a 3-fold increase in the rate of filtrability and a 3-fold decrease in the TO 5 value can be observed. No increase in filtrability could be elicited by Xanthine-7-acetate even similar in the maximal applied concentration ( 10 uM). It is to be emphasized that the effective concentration of Oepogen is mucA lower than those of Orotaverine

this is and Xanthine-7-acetate, effect was elicited by Depogen.

the

reason

why a significantly

increased

PENTOXIFYLLINE

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Antiaggregatory

AND DERIVATIVES

699

effect

The antiaggregatory activity of Depogen and its components and compared with those of acetylsalicylic acid (ASA), Drotaverine, Xanthine-7-acetate and Pentoxifylline.

were studied, Papaverine,

Inhibitory effects of the tested drugs against platelet aggregation, arachidonic acid (AA) and A 23187 Ca ionophore are induced by ADP, collagen, summarized in Table 2. and in Figure 4.

INHIBITIONOF RABBIT PLATELET AGGREGATION INDUCED BY VARIOUS STIMULI

IN VITRO

5000

.:

4000

i

3000

_.’

2000

:’

1000 j 0 1

ASA Arachidonsav Figure

4.

PENTOX.

PAPAVERINE

DROTA

&!!BJ Collagen

values of antiaggregatory I%0 platelets rabbit platelets collagen, induced by A 23187 Ca ionoahore.

m

A_23187

OEPOGEN ADP

effects of tested drugs on rabbit The aggregation were iii vitro. acid and arachidonic ADP ,

demonstrate that Depoogerr has a The table 2. and the Figure 4. clearly Effects of Depogen and Papaverine are antiaggregatory effect in vitro. potent is less active than Depogen. Antiaggregatory while Drotaverine comparable of Depogen is much higher than that of Pentoxifylline, Depogen being potency 5 - 10 times more active. Drotaverine is about two times less active than The one component of Depogen, the other component, Xantine - 7 - acetate has not that of Depogen, range. The active /uM concentration antiaggregatory effect at 10 - 1000 of Depogen is Drotaverine, but xanthine - 7 - acetate significantly component increase the antiaggregatory effect of Drotaverine. and Pentoxifylline are presented The antiaggregatory effects of Depogen by ADP. Depogen proved to in Figure 5. Human platelet aggregation was induced be 4 times more potent than Pentoxifylline, its IC50 value being 900 /uM/l.

PENTOXIFYLLINE

700

AND DERIVATIVES

Vol. 66, No. 6

Table 2 Antiaggregatory effect of PziTylline, Depogen, Papaverine, Drotaverine, ASA and Xanthine 7 - acetate on rabbit platelets in vitro. Aggregating agents ADP Collagen AA A 23187

ASA

4050 2610 780 2440

-4

Figure

5.

IC 0 Qwl) DROTAVER 2 NE PAPAVERINE 190 740 270 580 130 810 840 1060

PENTOXIFYLLINE 2660 2050 1870 2770

-1,s

-J

-2,s

-2

DEPOGEN 247 240 240 230

log

c WI)

The antiaggregatory effect of P and DRA on ADP induced are Mean 2 SEM of 4-6 aggregation in human PRP. Results separate experiments.

antiaggregatory The activities of Drotaverine and Depogen , Pentoxifylline were measured ex vivo after an intravenous injection or intragastric administration in anaesthetised rabbits. The antiaggregatory acitvity of the compounds in the ex vivo experiments was measured against ADP. Pentoxifylline in jetted even intravenously has only a very weak antiaggregatory action. At a dose level of 100 mg/kg its inhibitory effect is 40 %. The iv. DRA between the doses of 1 mg/kg and 7.5 mg/kg showed dose dependent antiaggregatory action. The ID50 value of the compound was 7 mg/kg (Figure 6.). The iv. administered Drotaverine is less active than Depogen, but this effect is not significantly. The antiaggregatory effects of Depogen and Pentoxifylline after intragastric administration were studied ex vivo in anaesthetized rabbits. Between the doses of 100 mg/kg and 300 mg/kg, Oepogen and Drotaverine showed a similar dose-dependent inhibition of platelet aggregation in rabbits, 300 mg/kg Depogen exerted the 50% inhibitory effect. At the dose level of 200 ;":kg Depogen proved to be 4 times more effective than Pentoxifylline (Figure . .

Vol.66, No.6

’ 70 -

PENTOXIFYLLINEAND DERIVATIVES

THE EX

VIVO

ANTIAGGREGATORY

PENTOXIFYLLINE, I

I

50.

;

30-T I

N

DEPOGEN,

- 7 -ACETATE

T 1’

l

40 -.1

0

AN0 XANTHINE

ADMINISTER0

l

B

I

OF I.V.

CO--

N H

OROTAVERINE

ACTIVITY

701

20

--

1G

-‘-

T

- I:! I 2

fs0

0.250

0.750

I.250

1.750

log 0 OEPOGIlN

Figure

6.

a

OROTAVERINE

0

PENTOXIFYLLINE

Oose

2.25ij (mg/kg)

A XANTIIINE - 7 - ACCTATE

Dose response curves of ex vivo antiaggregatory effects Pentoxifylline, Depogen, Drotaverine and Xanthine-7-acetate ADP-induced aggregation in anaesthetised rabbits, 1 hour after i.v. bolus injection of drugs. Results are Means 2 SEM. of 4 separate experiments.

of on the - 8

We have found that indomethacin, BW-755 C, and Depogen (at micromolar concentrations) each inhibit the aggregation of human leukocytes induced by arachidonic acid. Depogen inhibits human leukocyte aggregation induced by arachidonic acid, lC50 = 562 iuM/l. Depogen exerted 1.5 times weaker effect than BW-755 C, and its action corresponds to that of Indomethacin. BW-755 C is a powerful antiinflammatory drug, inhibits cyclooxygenase and lipoxygenase enzymes. Pentoxifylline and xantine - 7 acetate are ineffective in this test (Table 3.) Table 3. Antiaggregatory effect of Depogen, Pentoxifylline, Drotaverine, Xanthine-7acetate, BW-755 C and Indomethacin on arachidonic acid induced human leukocytes aggregation in vitro. COMPOUNDS BW -755 c

Indanethacin Oepogen Orotaverine Xanthine-7-acetate Pentoxifylline

1c503:6uM’1) 870 562 800

1500 1500

702

PENTOXIFYLLINE

THE

EX VIVO

OEPOGEN,

75

100 0

OEPOCEN

ANTIAGGREGATORY

PENTOXIFYLLINE,

A

OROTAVERINE

Effects

of P and DRA on Platelet

200

‘I 75

150

7.

ACTIVITY

OROTAVERINE

125

Figure

AND DERIVATIVES

0

OF ORALLY

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ADMINISTERED

AND

XANTHINE

225

25G

-

7 -

275

ACETATE

300 325 Dose hQ/Ql)

A XANTHINE- 7 - ACETATE

PENTOXIFYLLINE

Dose response curves of ex vivo antiaggregatory effects of Pentoxifylline, Depogen, Drotaverine and Xanthine-7-acetate on ADP-induced aggregation in anaesthetised rabbits, 1 hour after the orally administration of drugs. Results are Mean f_ SEM. of 4-8 separate experiments. Factor

3 availability

Collagen, at a dose of 4 jug/ml, caused a shortening of control Stypven clo-tting time. Preincubation of PRP with Pentoxifylline or Depogen before adding collagen lengthened the Stypven time (Figure 8.). At a concentration of 200 /ug/ml, Depogen prolonged clotting time significantly (p 0.05). At this concentration, Pentoxifylline prolonged clotting time too, but not significantly.

2S.O’

20.0.

1s.o.

i”*o* -igure

5.0

a. The effect availability

10.; of Pentoxifylline .

If.0

20.0

and Depogen

Incubation

on collagen

tlra (mln) induced

PF 3

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The in vitro effect of Depogen on red cell filtrability may have an important role in the therapeutic effects of the drug. It can be seen from the results that Depogen - similarly to that of Pentoxifylline - may improve the filtrability of erythrocytes of decreased plasticity, exposed to increased friction and shear stress in the rigid, narrow capillary vessels. By this way it may improve the oxygen supply to the tissues. It is emphasized that this should be taken into consideration while establishing therapeutic doses that the improvement obtained by excessively high doses is smaller than that produced by the administration of the optimum concentration. Since a maximum improvement of filtrability can be obtained by the administration of lower Depogen concentrations, the possible adverse reactions may also be more safely avoided. At present, the molecular mechanism of the in vitro increase in plasticity is not yet known in detail.

Rabbit platelet aggregation was induced by ADP, arachidonic acid, and A-23187 Ca ionofor, collagen and the antiaggregatory effect of Pentoxifylline, Drotaverine, Depogen, acetilsalycilic caid, papaverint: and xantine - 7 - acetate were compared. Depogen and papaverine seemed to be the most active among them. According to our results the antiaggregatory action of Depogen is stronger, it is about 5 to 10 times more active than that of Pentoxifylline in vitro. Its activity is in the range of acetylsalicylic acid. Here we should emphasize that only Oepogen exerted a dose-dependent Ca ionofor but not the other two. This antiaggregatory activity against directs our attention to a possibility of intracellular Ca release. or a Ca channel blocking ef feet . Although Depogen and acetylsalicylic acid have similar antiaggregator) activities in but they exert it via different mechanisms. vitro, Acetylsalicylic acid inhibits platelet TxA2 production by blocking platelet it exerts its inhibitory effect on the cyclooxygenase. At the same time endothelium, by inhibiting the biosynthesis of prostacyclin (PG12). too, inhibits platelet cyclooxygenase irreversibly by Acetylsalicylic acid acetylation residue in of a serine cyclooxygenase. The platelets are not and cannot regenerate (14). However, the able to synthesize this enzyme, able to synthesize this protein, thus, the cyclooxygenase endothelium is can be regenerated (4,8). Oepogen enhances prostacyclin enzyme system synthesis and inhibits the synthesis of TXA2 through the elevation of CAMP This is the basis of its levels via inhibiting phosphodiesterase. phosphodiesterase blocking effect can be action. The antiaggregatory demonstrated both in platelets and in the endothelium (23). When platelet of slopes displayed application proved to

both drugs were injected aggregation induced by dose - response curves namely slight effect. the two drugs as of be 4 times more effective

as i .v. bolus in anaesthetised rabbits and AOP, tested ex viva, great differences in could be demonstrated, Pentoxifylline were obtained by oral Similar results well, but a dose level of 200mg/kg Depogen than Pentoixifylline.

It is well known from the literature that phospholipids involved in the intrinsic pathway of blood coagulation originate mainly from platelets (6,281. a very powerful platelet activator, The treatment of platelets with collagen, but results in the and release reaction, not only aggregation causes increased a phospholipid-related procoagulant activity, development of availability of platelet factor 3 (15). Our experiments suggest, that Depogen

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because it inhibits platelet is an effective inhibitor of platelet activation, aggregation and prevents the development of platelet factor 3 activity, too. to the effect of Depogen on human leukocyte Particular attention was paid induced by arachidonic acid. Antiaggregatory effect aggregation in vitro, could be demonstrated as a characteristic feature of anti-inflammatory drugs. or BW-755C, Depogen exerted a significant with indomethacin In comparison of Pentoxifylline could be observed. Otherwise, Oepogen ef feet , but no effect did not show any anti-inflammatory activity, which also reflects its special and selective action on the blood cells. Our new compound Oepogen consists of two constituents: Drotaverine and Xanthine - 7 - acetate. Orotaverine has biological activity on examined tests, but Xanthine - 7 acetate exerts no significant biological effect at 10 - 1000 /uM/l concentration range. The haemorrheological and in vitro antiaggregatory significantly higher than that of Drotaverine and effect of Depogen is - 7 - acetate. These results suggest, that the biologically inactive Xanhtine - 7 - acetate increases the biological effect of Drotaverine. Xanthine Xanthine - 7 - acetate potentiates the effect of Drotaverine and this effect could be an explanation of the fact, that the biological potency of Depogen is The mechanism of this action is significantly higher than that of Drotaverine. unknown yet, but the reason of this phenomenon is being researched. The experiments demonstrate the haemorrheologic activity of our new drug called Depogen. Beside its vasodilator effect (23) it can improve the decreased filtrability of red cells which is an important blood factor in the deterioration of microcirculation. It seems more effective than Pentoxifylline. is more in the Depogen effective than Pentoxifylline antiaggregatory tests, in the RBC filtrability test and Depogen has a more effective vasodilator activity. All these three effects of Depogen have a special importance in the successful treatment of obliterative peripheral vascular diseases.

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plasmatische Verschluss

BORN, G.V.R. and CROSS M.J. The aggregation (Land.). 168. 178-195, 1963 BURCH, synthetase DEGUCHI, Clinical function.

J.W. and STANFORD P.W. by oral aspirin. J. Clin.

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and UEND, H. and platelet

BODE, A.P. and LENTZ, B.R. Differentation of factor V-like from catalytic phospholipid - like surface activity in membrane derived from human platelets. Throm. Res. 22. 603, 1981

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7

ITOH, T., SATOH, T. Influence of pentoxifylline ( Trental > on platelet aggregation and serum lipids in patients with obstructive cerebrovascular disorders. Pharmatherapeutica '2. 159-164, 1979

8

of endothelial cell prostacyclin JAFFE, E.A. and WEKSLER, 8. B. Recovery production after inhibition by low doses of aspirin. J. Clin. Invest. 63. 532-535, 1979

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KAPUI, Z., TAROOS, L., HERMECZ, I., STAOLER, Comparative Studies with Orotaverine-Acephyllinate Thrombosis and Haemostasis 62. 349, 1989

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10 LEONHAROT., H. and GRIGOLEIT, H.G. Effects of pentoxifylline on red blood cell deformability and blood viscosity under hyperosmolar conditions. Naunyn-Schmiedeberg's Archives of Pharmachology 299. 197-200, 1977 11 MULLER, R. On the therapy of disturbances 226-234, 1985

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