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Prolonged inhibition of ex vivo sodium arachidonate-induced platelet aggregation and malondialdehyde (MDA) production by sulphinpyrazone (anturan) in man
THROMBOSIS RESEARCH 21; 321-327, 1981
0049-3048/81/030321-07$02.00/O Printed in the USA. Copyright (c) 1981 PergamonPress Ltd. All rights reserved.
PROLONGED INHIBITION OF EX VIVO SODIUM ARACHIDONATE-INDUCED PLATELET AGGREGATION AND MALONDIALDEHYDE (MDA) PRODUCTION BY SULPHINPYRAZONE (ANTURAN) IN MAN
E.D. Maguire, G.F. Pay, R.B. Wallis and A.M. White Horsham Research Centre, Ciba-Geigy Pharmaceuticals Division, Wimblehurst Road, Horsham, West Sussex RH12 4AB, England
(Received 9.5.1979;in revised form 2.7.1979,29.2.1980.
Acceptedhy Editor V.V. Keklcar. Received in final form by ExecutiveEditorialOffice 29.1.1981*)
A single dose (400 mg) of sulphinpyrazone inhibits both platelet aggregation and platelet malondialdehyde biosynthesis induced by sodium arachidonate. The inhibitory effect lasts for 72 h and 24 h respectively which is much longer than the life of sulphinpyrazone or its known metabolites in the plasma. INTRODUCTION
It has been demonstrated in rabbits that sulphinpyrazone, given in high dosage, exerts a prolonged inhibition of collagen-induced thrombocytopenia (1). After intravenous injection of the drug (100 mg/kg) the transient loss of circulating SlCr-labelled platelets brought about by an infusion of soluble collagen was almost halved 30 min and 18 h after drug administration. A similar prolonged effect was seen with respect to inhibition of platelet malondialdehyde (MDA) production. Collagen-induced
platelet aggregation in plateletrich plasma (PRP) is not sensitive to inhibition in the range of plasma sulphinpyrazone concentrations (between 10 IJMand 70 PM) (2,3) which are likely to be achieved on the drug
* We are very much distressed,as is the editor, to learn that the manuscript of this paper sent Mce to this office was lost each time in the mail. This has never happened before in the history of our Journal and we deeply regret these unfortunate occurrences. Executive Editorial Office 321
322
SULPHIRF'YRAZONE IN HAN
Vo1.21,No.3
regimens of 600 mg/day or 800 mg/day utilised in the major clinical trials (4,5,6,7). We found that sodium arachidonateinduced platelet aggregation was inhibited -ex vivo subsequent to ora1 dosing of rabbits (unpublished results) and guinea pigs (8) with relatively 1OW doses of the drug and thus we were able to Confirm the results of Buchanan, et al. (1) in both these species using this methodology. We thought therefore that this technique would be a suitable one with which to search for the existence of the prolonged effect in man. The preliminary results described here confirm the existence of such an effect. MATERIALS AND METHODS Five normal male volunteers aged 34-51 participated. These volunteers gave signed informed consent and they had not ingested aspirin or other non-steroidal anti-inflammatory drugs for at least two weeks prior to the study. Blood samples were taken 5 days before, immediately before and 2, 4, 8, 12, 24, 48 and 72 h after ingestion of 2 x 200 mg sugar coated tablets of sulphinpyrazone (Anturan) followed by approximately 100 ml water. The subjects were fasted for at least 6 h before taking the sulphinpyrazone, had a standard breakfast 1 h afterwards and had standardised meals during the first day of the trial. Blood samples (20 ml) were withdrawn from the antecubital vein and rapidly mixed with 2 ml O.lM sodium dihydrogen citrate adjusted to pH 6.5 with NaOH. Platelet-rich plasma (PRP) was prepared by centrifugation at 250 g for 20 min at 20°C and platelet-free plasma by centrifugation of a sample of the PRP at 11000 g for 2 min. PRP was stored in capped polythene tubes during the experimental measurement period (approximately 2 h). The mean platelet count of the group did not statistically significantly change during the study (range of means 2.2 - 3.2 x 108 platelets/ml). Dose-response curves for platelet aggregation induced by dilutions of sodium arachidonate (25 mg/ml) or adenosine diphosphate (1 mg/ml) were measured on each s,ampleof PRP (0.4 ml) in a Payton platelet aggregometer. Aggregation rates were determined by drawing a tangent to the aggregometer trace8 at a point between 5% and 10% of the total deflection. Arachidonic acid was dissolved in O.lM Na CO and stored under 0 -free N in an injection vial for ths ddration of the experimsnt (8 diys) . Blood samples were withdrawn from a sixth untreated subject 5 days before the trial and on day 3 of the trial and the dose-response curve of platelet aggregation induced by sodium arachidonate was measured in order to check the stability of the stock solution of sodium arachidonate. Malondialdehyde biosynthesis was measured in samples of washed platelets. Platelets were washed by first forming platelet aggregates through the addition of ADP (20 ~1, 1 mg/ml) to PRP (4 ml) and agitating the mixture with a siliconised Pasteur pipette (9). When large aggregates had been obtained 4 ml of NO. 1 buffer was added and tge suspension was centrifuged at 170 g for 5 min at 20 C. The supernatant was discarded and the platelet pellet was resuspended in NO. 2 buffer. Platelet recovery throughout the procedure was 85.3 t 3.7%. Malondialdehyde production was induced by addition of lo PM sodium arachidonate and incubating the
323
SIJLPHINPYRAZONE IN MAN
Vo1.21, No.3
platelets at 37% for 15 min in a shaking water bath. Malondialdehyde was estimated using the thiobarbituric acid method (10) by comparison with a standard curve (11). Platelet concentrations were measured using a Coulter counter with appropriate standard procedures. Sulphinpyrazone concentrations in samples of platelet-free plasma were measured spectrophotometrically (12). Buffer No. 1 contained in 1 litre, 4.2 g NaCl, 0.047 g Na2HPO4, 0.106 g NaH2PO4, and 20 g EDTA. Buffer No. 2 contained in 1 litre, 1 g glucose, 8 g NaCl, 0.2 g KCl, 0.047 g Na2HPO4, 0.106 g NaH2PO4, 0.475 g MgC12. Each buffer was adjusted to pH 6.5 with 4N NaOH and had an osmolarity of 360 mOsm. Experimental data were analysed by the paired t-test.
[AA] (pM.)
a. . . ‘+__+
600-
I
1
10 MDA nmo es/ ( 10!!Ipits.) 5
,
,
024
.
8
12 Time
- - - -----2448 (hours)
FIG. 1 The effect of sulphinpyrazone on platelet function ex vivo. Curve a (+_) is the change inED=or sodium arachidonate aggregation compared to control at time 0. The ED50 of the control was 480 LIM. Curve b (--t-1 is the MDA production induced by sodium 2rachidonate. Results are shown - standard error. + denotes results which are statistically significant (p < 0.05) from the results at time zero.
72
324
SULF'HINPYRAZONE IN MAN
Vo1.21,No.3
RESULTS Sulphinpyrazone (400 mg) caused prolonged inhibition of the rate of sodium arachidonate-induced platelet aggregation ex vivo up to 72 h after a single dose (Fig. la). The maximum rat-and the total extents of aggregation were not affected by sulphinpyrazone treatment. Log sodium arachidonate concentration versus response curves (Fig. 2) were shifted to higher sodium arachidonate concentrations and the curves were parallel to control curves indicating competitive inhibition at the early times. At later times the type of inhibition was less clear and there may be an element of non-competition. Two typical examples are shown in Fig. 2.
10
FIG. 2 The effect of sulphinpyrazone on platelet aggregation induced by sodium arachidonate. Log sodium arachidonate concentration versus platelet aggregation rate for blood samples taken before t--t-) and 2 h t--E_) and 24 h C--e-) after a single 400 mg tablet of sulphinpyrazone are shown. Result& are shown t standard error.
Vo1.21, No.3
SULPHINPYRAZONEIN MAN
325
In view of the complexity in interpretation of platelet aggregation curves it was felt necessary to measure the threshold concentration of sodium arachidonate just sufficient to cause aggregation within 2 min of its addition. Using this method, the same type of time profile as in Fig. la was obtained. The stability of the stock solution of sodium arachidonate was investigated by measuring, in a control subject, the change in ED for aggregation of PRP after the solution had been kept fo1'8 days. The results showed that decomposition occurred to the extent of 3% per day and this would not have affected the outcome of the study. Sulphinpyrazone also inhibited platelet malondialdehyde biosynthesis induced by sodium arachidonate (10 uM) ex vivo. Inhibition was statistically significant at 2 h (42.8%), 4 h (50.0%) and again at 24 h (14.2%) after the single sulphinpyrazone dose (Fig. lb). The highest sulphinpyrazone plasma concentration was found in the 2 h samples and this had declined to zero by 24 h. There was no statistically significant effect of sulphinpyrazone on ADP-induced primary aggregation up to 48 h after its administration, nor was there any effect on the plasma platelet count. DISCUSSION The daily doses of sulphinpyrazone which have been shown to confer positive therapeutic benefit in clinical trials relating to thrombosis are 600 mg (200 mg t.d.s.) (4,5) or 800 mg (200 mg q.d.s.) (7) and considerable effort has been expended,on the question of whether or not there are any ex vivo effects of the drug at these dose levels. Results were negative until Ali and McDonald (13) demonstrated that after 900 mg/day and 1600 mg/day for 4 days a dose-dependent, partial inhibition of collagen-induced platelet secretion could be seen which increased in extent as the collagen concentration was decreased. The results reported here show an ex vivo effect Of the drug on human platelet function after a single opposed t0 multiple drug dosage. Sodium arachidonate, because of its steep concentration versus response curve proved superior to.collagen for detecting drug effects in that platelet inhibition was demonstrated after 400 mg whereas a dose of 800 mg was necessary before the inhibition of collagen-induced aggregation was detectable ex vivo (Pfister, et al., private communication). Unfortunately, however, it was difficult to detect any effects after a single 200 mg dose using sodium arachidonate as the agonist. Trends were obtained which were only Statistically significant at 4 h. Our results which include measurement Of MDA production as an indirect indicator of the intactness Of the prostaglandin pathway are consistent with the results of Ali and McDonald (13) in so far as they support the notion that sulphinpyrazone would exert its platelet inhibitory effects through competitive inhibition of prostaglandin biosynthesis. They contain, however, the additional information that even in low doses in man there is a prolonged effect as was first shown by Buchanan, et al., in rabbits at a high dose of the drug (1).
326
SULPHINPYRAZONE IN HAN
Vo1.21,No.3
The metabolism of sulphinpyrp$one in man is such that 24 h after a single dose of 200 mg of C-labelled drug the plasma level of unchanged drug and major metabolites are below the limits of detection (3). A similar situation pertained after the 800 mg dose where a high pressure liquid chromatographic method was used for the determination of drug concentration (Pfister, et al., private communication) and in the study reported here where a simple spectrophotometric method was used. Any metabolite of sulphinpyrazone responsible for the later part of'the prolonged effect would therefore have to be an extremely potent inhibitor of platelet function. The nature of the effect is therefore not readily understandable at present. The means through which sulphinpyrazone exerts its clinical effects remains obscure and in particular recent results showing reduction of sudden death subsequent to myocardial infarction (7) are only indirectly explicable on the basis of suppression of platelet function. However, the results reported by us suggest that such suppression is still very likely to constitute an important aspect of the mode of action of the drug although other properties such as ability to protect the endothelium (14) could also have great significance. 1.
REFERENCES BUCHANAN, M.R., ROSENFELD, J. and HIRSH, J. The prolonged effect of sulfinpyrazone on collagen-induced platelet l3, 883-892,1978. aggregation __ in viva. Thromb.E.,
2.
ROSENFELD, J., BUCHANAN, M.R., POWERS, P., HIRSH, J., BARNETT, H.J.M. and STUART, R.K. Determination of sulfinpyrazone in patient plasma by gas chromatography. 12, 247-255,1978. Thromb.&.,
3.
DIETERLE, W., FAIGLE, J.W., MORY, H., RICHTER, W.J., THEOBALD, W. Biotransformation and pharmacokinetics of sulphinpyrazone (Anturan) in man. EUrOP.&&&. Phrrrmacol.,2, 135-145,1975.
4.
EAEGI, A., PINEO, G.F., SHIMIZU, A., TRIVEDI, H., HIRSH, J. GENT. M. Arterio-venous shunt thrombosis. Prevention by Enal. 2. &Q., m, 304-306,1974. sulphinpyrazone. m
5.
EAEGI, A., PINEO, G.F., SHIMIZU, A., TRIVEDI, H., HIRSH, J., and GENT, M. The role of sulfinpyrazone in the prevention of arterio-venous shunt thrombosis. Circulation, 52, 497-499, 1975.
6.
EVANS, G. and GENT, M. Effect of platelet suppressive druss on arterial and venous thromboembolism. In: J. Hirsh, J.F. Cade, s.) Basel-M(lnchen-ParisLondon-New York-Sydney: S. Karger, 1975, p. 258-262.
7.
The Anturane Reinfarction Trial Research Group. Sulfinpyrazone in the prevention of cardiac death'after 298, 289-295,1978. myocardial infarction. Nx En&& 3. &&,
Vo1.21, No.3
SULPHINPYRAZONE IN HAN
327
8.
BUTLER, K.D., WALLIS, R.B. and WHITE, A.M. A study of the relationship between ex vivo and in vivo effects of sulphinpyrazone in thrguinea pig. - sstasis, K, 853-860, 1979.
9.
MOHAMED, S.F., REDDICK, R.L. and MASON, R.G. Characterisation of human platelets separated from blood by ADP-induced aggregation. &=r. 2. Pathol., & 81-91,1975.
10.
STUART, M.J., MURPHY, S. and OSKI, F.A. A simple nonradioisotope technique for the determination of platelet life-span. New Engl. 2. -Med., 292, 1310-1313, 1975.
11.
SMITH, J.B., INGERMAN, C.M. and SILVER, M.J. Malondialdehyde formation as an indicator of prostaglandin production 88, 167-172,1976. by human platelets. &. &a&. CA. MA,
12.
BURNS, J.J., YU, T.F., RITTERBRAND, A., PETEL, J.M., GUTMAN, A.N. and BRODIE, B.B. A potent new uricosuric agent, the sulfoxide metabolite of the phenylbutazone ., 119, 418-426, analogue, G-25671. J. Pharmacol. a& Exp. 1957.
13.
ALI, M. and MCDONALD, J.W.D. Effects of sulfinpyrazone on platelet prostaglandin synthesis and platelet release of 868-875,1977. serotonin. L. Lab. --- Clin. Med., 89,
14.
HARKER, L.A., WALL, R.T., HARLAN, J.M. and ROSS, R.
Sulfinpyrazone prevention of homocysteine-induced endothelial cell injury. Clin. Rs., &4, 554A, 1978.
0049-3048/81/030321-07$02.00/O Printed in the USA. Copyright (c) 1981 PergamonPress Ltd. All rights reserved.
PROLONGED INHIBITION OF EX VIVO SODIUM ARACHIDONATE-INDUCED PLATELET AGGREGATION AND MALONDIALDEHYDE (MDA) PRODUCTION BY SULPHINPYRAZONE (ANTURAN) IN MAN
E.D. Maguire, G.F. Pay, R.B. Wallis and A.M. White Horsham Research Centre, Ciba-Geigy Pharmaceuticals Division, Wimblehurst Road, Horsham, West Sussex RH12 4AB, England
(Received 9.5.1979;in revised form 2.7.1979,29.2.1980.
Acceptedhy Editor V.V. Keklcar. Received in final form by ExecutiveEditorialOffice 29.1.1981*)
A single dose (400 mg) of sulphinpyrazone inhibits both platelet aggregation and platelet malondialdehyde biosynthesis induced by sodium arachidonate. The inhibitory effect lasts for 72 h and 24 h respectively which is much longer than the life of sulphinpyrazone or its known metabolites in the plasma. INTRODUCTION
It has been demonstrated in rabbits that sulphinpyrazone, given in high dosage, exerts a prolonged inhibition of collagen-induced thrombocytopenia (1). After intravenous injection of the drug (100 mg/kg) the transient loss of circulating SlCr-labelled platelets brought about by an infusion of soluble collagen was almost halved 30 min and 18 h after drug administration. A similar prolonged effect was seen with respect to inhibition of platelet malondialdehyde (MDA) production. Collagen-induced
platelet aggregation in plateletrich plasma (PRP) is not sensitive to inhibition in the range of plasma sulphinpyrazone concentrations (between 10 IJMand 70 PM) (2,3) which are likely to be achieved on the drug
* We are very much distressed,as is the editor, to learn that the manuscript of this paper sent Mce to this office was lost each time in the mail. This has never happened before in the history of our Journal and we deeply regret these unfortunate occurrences. Executive Editorial Office 321
322
SULPHIRF'YRAZONE IN HAN
Vo1.21,No.3
regimens of 600 mg/day or 800 mg/day utilised in the major clinical trials (4,5,6,7). We found that sodium arachidonateinduced platelet aggregation was inhibited -ex vivo subsequent to ora1 dosing of rabbits (unpublished results) and guinea pigs (8) with relatively 1OW doses of the drug and thus we were able to Confirm the results of Buchanan, et al. (1) in both these species using this methodology. We thought therefore that this technique would be a suitable one with which to search for the existence of the prolonged effect in man. The preliminary results described here confirm the existence of such an effect. MATERIALS AND METHODS Five normal male volunteers aged 34-51 participated. These volunteers gave signed informed consent and they had not ingested aspirin or other non-steroidal anti-inflammatory drugs for at least two weeks prior to the study. Blood samples were taken 5 days before, immediately before and 2, 4, 8, 12, 24, 48 and 72 h after ingestion of 2 x 200 mg sugar coated tablets of sulphinpyrazone (Anturan) followed by approximately 100 ml water. The subjects were fasted for at least 6 h before taking the sulphinpyrazone, had a standard breakfast 1 h afterwards and had standardised meals during the first day of the trial. Blood samples (20 ml) were withdrawn from the antecubital vein and rapidly mixed with 2 ml O.lM sodium dihydrogen citrate adjusted to pH 6.5 with NaOH. Platelet-rich plasma (PRP) was prepared by centrifugation at 250 g for 20 min at 20°C and platelet-free plasma by centrifugation of a sample of the PRP at 11000 g for 2 min. PRP was stored in capped polythene tubes during the experimental measurement period (approximately 2 h). The mean platelet count of the group did not statistically significantly change during the study (range of means 2.2 - 3.2 x 108 platelets/ml). Dose-response curves for platelet aggregation induced by dilutions of sodium arachidonate (25 mg/ml) or adenosine diphosphate (1 mg/ml) were measured on each s,ampleof PRP (0.4 ml) in a Payton platelet aggregometer. Aggregation rates were determined by drawing a tangent to the aggregometer trace8 at a point between 5% and 10% of the total deflection. Arachidonic acid was dissolved in O.lM Na CO and stored under 0 -free N in an injection vial for ths ddration of the experimsnt (8 diys) . Blood samples were withdrawn from a sixth untreated subject 5 days before the trial and on day 3 of the trial and the dose-response curve of platelet aggregation induced by sodium arachidonate was measured in order to check the stability of the stock solution of sodium arachidonate. Malondialdehyde biosynthesis was measured in samples of washed platelets. Platelets were washed by first forming platelet aggregates through the addition of ADP (20 ~1, 1 mg/ml) to PRP (4 ml) and agitating the mixture with a siliconised Pasteur pipette (9). When large aggregates had been obtained 4 ml of NO. 1 buffer was added and tge suspension was centrifuged at 170 g for 5 min at 20 C. The supernatant was discarded and the platelet pellet was resuspended in NO. 2 buffer. Platelet recovery throughout the procedure was 85.3 t 3.7%. Malondialdehyde production was induced by addition of lo PM sodium arachidonate and incubating the
323
SIJLPHINPYRAZONE IN MAN
Vo1.21, No.3
platelets at 37% for 15 min in a shaking water bath. Malondialdehyde was estimated using the thiobarbituric acid method (10) by comparison with a standard curve (11). Platelet concentrations were measured using a Coulter counter with appropriate standard procedures. Sulphinpyrazone concentrations in samples of platelet-free plasma were measured spectrophotometrically (12). Buffer No. 1 contained in 1 litre, 4.2 g NaCl, 0.047 g Na2HPO4, 0.106 g NaH2PO4, and 20 g EDTA. Buffer No. 2 contained in 1 litre, 1 g glucose, 8 g NaCl, 0.2 g KCl, 0.047 g Na2HPO4, 0.106 g NaH2PO4, 0.475 g MgC12. Each buffer was adjusted to pH 6.5 with 4N NaOH and had an osmolarity of 360 mOsm. Experimental data were analysed by the paired t-test.
[AA] (pM.)
a. . . ‘+__+
600-
I
1
10 MDA nmo es/ ( 10!!Ipits.) 5
,
,
024
.
8
12 Time
- - - -----2448 (hours)
FIG. 1 The effect of sulphinpyrazone on platelet function ex vivo. Curve a (+_) is the change inED=or sodium arachidonate aggregation compared to control at time 0. The ED50 of the control was 480 LIM. Curve b (--t-1 is the MDA production induced by sodium 2rachidonate. Results are shown - standard error. + denotes results which are statistically significant (p < 0.05) from the results at time zero.
72
324
SULF'HINPYRAZONE IN MAN
Vo1.21,No.3
RESULTS Sulphinpyrazone (400 mg) caused prolonged inhibition of the rate of sodium arachidonate-induced platelet aggregation ex vivo up to 72 h after a single dose (Fig. la). The maximum rat-and the total extents of aggregation were not affected by sulphinpyrazone treatment. Log sodium arachidonate concentration versus response curves (Fig. 2) were shifted to higher sodium arachidonate concentrations and the curves were parallel to control curves indicating competitive inhibition at the early times. At later times the type of inhibition was less clear and there may be an element of non-competition. Two typical examples are shown in Fig. 2.
10
FIG. 2 The effect of sulphinpyrazone on platelet aggregation induced by sodium arachidonate. Log sodium arachidonate concentration versus platelet aggregation rate for blood samples taken before t--t-) and 2 h t--E_) and 24 h C--e-) after a single 400 mg tablet of sulphinpyrazone are shown. Result& are shown t standard error.
Vo1.21, No.3
SULPHINPYRAZONEIN MAN
325
In view of the complexity in interpretation of platelet aggregation curves it was felt necessary to measure the threshold concentration of sodium arachidonate just sufficient to cause aggregation within 2 min of its addition. Using this method, the same type of time profile as in Fig. la was obtained. The stability of the stock solution of sodium arachidonate was investigated by measuring, in a control subject, the change in ED for aggregation of PRP after the solution had been kept fo1'8 days. The results showed that decomposition occurred to the extent of 3% per day and this would not have affected the outcome of the study. Sulphinpyrazone also inhibited platelet malondialdehyde biosynthesis induced by sodium arachidonate (10 uM) ex vivo. Inhibition was statistically significant at 2 h (42.8%), 4 h (50.0%) and again at 24 h (14.2%) after the single sulphinpyrazone dose (Fig. lb). The highest sulphinpyrazone plasma concentration was found in the 2 h samples and this had declined to zero by 24 h. There was no statistically significant effect of sulphinpyrazone on ADP-induced primary aggregation up to 48 h after its administration, nor was there any effect on the plasma platelet count. DISCUSSION The daily doses of sulphinpyrazone which have been shown to confer positive therapeutic benefit in clinical trials relating to thrombosis are 600 mg (200 mg t.d.s.) (4,5) or 800 mg (200 mg q.d.s.) (7) and considerable effort has been expended,on the question of whether or not there are any ex vivo effects of the drug at these dose levels. Results were negative until Ali and McDonald (13) demonstrated that after 900 mg/day and 1600 mg/day for 4 days a dose-dependent, partial inhibition of collagen-induced platelet secretion could be seen which increased in extent as the collagen concentration was decreased. The results reported here show an ex vivo effect Of the drug on human platelet function after a single opposed t0 multiple drug dosage. Sodium arachidonate, because of its steep concentration versus response curve proved superior to.collagen for detecting drug effects in that platelet inhibition was demonstrated after 400 mg whereas a dose of 800 mg was necessary before the inhibition of collagen-induced aggregation was detectable ex vivo (Pfister, et al., private communication). Unfortunately, however, it was difficult to detect any effects after a single 200 mg dose using sodium arachidonate as the agonist. Trends were obtained which were only Statistically significant at 4 h. Our results which include measurement Of MDA production as an indirect indicator of the intactness Of the prostaglandin pathway are consistent with the results of Ali and McDonald (13) in so far as they support the notion that sulphinpyrazone would exert its platelet inhibitory effects through competitive inhibition of prostaglandin biosynthesis. They contain, however, the additional information that even in low doses in man there is a prolonged effect as was first shown by Buchanan, et al., in rabbits at a high dose of the drug (1).
326
SULPHINPYRAZONE IN HAN
Vo1.21,No.3
The metabolism of sulphinpyrp$one in man is such that 24 h after a single dose of 200 mg of C-labelled drug the plasma level of unchanged drug and major metabolites are below the limits of detection (3). A similar situation pertained after the 800 mg dose where a high pressure liquid chromatographic method was used for the determination of drug concentration (Pfister, et al., private communication) and in the study reported here where a simple spectrophotometric method was used. Any metabolite of sulphinpyrazone responsible for the later part of'the prolonged effect would therefore have to be an extremely potent inhibitor of platelet function. The nature of the effect is therefore not readily understandable at present. The means through which sulphinpyrazone exerts its clinical effects remains obscure and in particular recent results showing reduction of sudden death subsequent to myocardial infarction (7) are only indirectly explicable on the basis of suppression of platelet function. However, the results reported by us suggest that such suppression is still very likely to constitute an important aspect of the mode of action of the drug although other properties such as ability to protect the endothelium (14) could also have great significance. 1.
REFERENCES BUCHANAN, M.R., ROSENFELD, J. and HIRSH, J. The prolonged effect of sulfinpyrazone on collagen-induced platelet l3, 883-892,1978. aggregation __ in viva. Thromb.E.,
2.
ROSENFELD, J., BUCHANAN, M.R., POWERS, P., HIRSH, J., BARNETT, H.J.M. and STUART, R.K. Determination of sulfinpyrazone in patient plasma by gas chromatography. 12, 247-255,1978. Thromb.&.,
3.
DIETERLE, W., FAIGLE, J.W., MORY, H., RICHTER, W.J., THEOBALD, W. Biotransformation and pharmacokinetics of sulphinpyrazone (Anturan) in man. EUrOP.&&&. Phrrrmacol.,2, 135-145,1975.
4.
EAEGI, A., PINEO, G.F., SHIMIZU, A., TRIVEDI, H., HIRSH, J. GENT. M. Arterio-venous shunt thrombosis. Prevention by Enal. 2. &Q., m, 304-306,1974. sulphinpyrazone. m
5.
EAEGI, A., PINEO, G.F., SHIMIZU, A., TRIVEDI, H., HIRSH, J., and GENT, M. The role of sulfinpyrazone in the prevention of arterio-venous shunt thrombosis. Circulation, 52, 497-499, 1975.
6.
EVANS, G. and GENT, M. Effect of platelet suppressive druss on arterial and venous thromboembolism. In: J. Hirsh, J.F. Cade, s.) Basel-M(lnchen-ParisLondon-New York-Sydney: S. Karger, 1975, p. 258-262.
7.
The Anturane Reinfarction Trial Research Group. Sulfinpyrazone in the prevention of cardiac death'after 298, 289-295,1978. myocardial infarction. Nx En&& 3. &&,
Vo1.21, No.3
SULPHINPYRAZONE IN HAN
327
8.
BUTLER, K.D., WALLIS, R.B. and WHITE, A.M. A study of the relationship between ex vivo and in vivo effects of sulphinpyrazone in thrguinea pig. - sstasis, K, 853-860, 1979.
9.
MOHAMED, S.F., REDDICK, R.L. and MASON, R.G. Characterisation of human platelets separated from blood by ADP-induced aggregation. &=r. 2. Pathol., & 81-91,1975.
10.
STUART, M.J., MURPHY, S. and OSKI, F.A. A simple nonradioisotope technique for the determination of platelet life-span. New Engl. 2. -Med., 292, 1310-1313, 1975.
11.
SMITH, J.B., INGERMAN, C.M. and SILVER, M.J. Malondialdehyde formation as an indicator of prostaglandin production 88, 167-172,1976. by human platelets. &. &a&. CA. MA,
12.
BURNS, J.J., YU, T.F., RITTERBRAND, A., PETEL, J.M., GUTMAN, A.N. and BRODIE, B.B. A potent new uricosuric agent, the sulfoxide metabolite of the phenylbutazone ., 119, 418-426, analogue, G-25671. J. Pharmacol. a& Exp. 1957.
13.
ALI, M. and MCDONALD, J.W.D. Effects of sulfinpyrazone on platelet prostaglandin synthesis and platelet release of 868-875,1977. serotonin. L. Lab. --- Clin. Med., 89,
14.
HARKER, L.A., WALL, R.T., HARLAN, J.M. and ROSS, R.
Sulfinpyrazone prevention of homocysteine-induced endothelial cell injury. Clin. Rs., &4, 554A, 1978.