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Identification and renal excretion of probenecid metabolites in man
r e 3~~nc~~~V~~ 9~ria.rt I, pp. 1337-1343, 1970.
Pergamon Press
IDENTIFICATION AND RENAL EXCRETION OF PROBENECID MLTABOLITEB IN MANf James M. Perel, Robert F . Cunaiaghem, Henry M. Fales and Peter G. Dayton Depts . of Medicine (Clinical Pharmacology) end Gàemietry Emory University School of Medicine, Emory University, Atlaata,Ga . 30322 sad Molecular Diseases Breach, National Heart and Luag Institute, NIH, Betheada, Maryland 20014 U . S. A.
(Received 28 August 1970; in find form 8 October 1970)
Recently Guarino et all;(1) have reported the identification of several metabolites of probenecid (P)+ from rat bile .
Similarly, our experiments++
with ring l4 C probenecid in man, indicate that only a Fraction of the radio activity in urine could be accounted for as unchanged P and as probenecid aryl mono-glucuronide(PAG) (2) .
The present report deals with the identifi-
cation and qusatitation of essentially all the metabolites found is the urine of subjects receiving probenecid . Methods and Results Two normal subjects xere administered 2 g of P es a single oral dose (2g of P end 10 Nc of 14C-P were dissolved is ethanol sad evaporated to dryness) . Fractional urine collectiaae were stored in the presence of toluene (1 ml/1) and 50x acetic acid (20 ml/1) ; heparinized plasma was stored at -200. biological material was acidified xith
lOZ
of its volume of
extracted txice with two times its volume of ethyl acetate .
6
The
N HC1 sad
The eztract wes
brought to dryness in vacuo at 350 , the residue xes dissolved in ethanol end applied to silica gel G (Merck) plates sad chrcmatographed in solvent system I, benzene : ethyl acetate : acetic acid (7 :3 :1) .
Mesa spectrometric and gas
a Thia work xas supported in part by Grant CM 142g0 from the National Institute of General Medical Sciences, National Institutes of Health . }; Due to typographical error, the mass spectra of Metabolites A and C were inverted in this paper. + Probenç cid = HenemidR . ++ The 14C-P xas a gift from Dr . J. E . Beer, Merck Sharp b Dohme, West Point, Penasylveaia .
1337
METAHOLISM OF PROHENECiD
1338
Yol . 9, No. 23
chromatographic techniques were the same as previously described (1) . 14 C was counted in ea LS 250 Bechaa liquid scintillation spectrometer . tillation cocktail was prepared as follows :
to 1 L of toluene,
The scin
7
g of PPO,
0 .36 g POPOP end 200 ml Bio-Soly BB3-3 (Beckman) were added . The nomenclature and structures deacribèà in this report are the same es those used previously (1) end are the follwing : Metabolite A,p-(N-propyl, N-2-hydroxyprapylsulfamoyl) benzoic acid ; Metabolite B, p-(N-propyl, N-2 carbo~grethylsulfamoyl) benzoic acid4
Metabolite C, p-(N-propyl, N-3-hydroxy-
propyleulfamoyl) benzoic acid ; R-depropyl metabolite, p-(propylsulfamoyl) benzoic acid .
Metabolites A}, B and the R-depropyl metabolite were obtained
in crystalline form by removing appropriate silica gel areas off thin-layer plates and extracting with ethyl acetate .
After repeating the chromatographic
end extractive procedures, the oily residue which resulted upon evaporation to dryness, was dissolved is a minimum volume of ethanol, treated with charcoal sad crystallized twice from ethanol-water. niques, metabolite C was only obtained as an oil.
Using the same techTable 1 lists the melting
polst canateate end the relative chromatographic mobilitiee of the metabolitee~ PAG and P in two different solvent systems. Ia addition to gas chromatographic sad mass spectrometric cheracterization .of each metabolite, the N-depropyl metabolite and A were also compared with authentic materials on thin-layer chromatography sad with mined melting point determinations .
The carbon, hydrogen and nitrogen analysis}a of
metabolite H gave the following results : Calcd. for H, 5.43 ; N,
+
4.44 .
Ç13H17N06S :
C, 49 .524
Found: C, 49 .10 ; H, 5.40 ; N, 4 .20.
Isolated Metabolite A was found to be in the racemic form . Elemental analysis obtained through the courtesy of Mr .Kermit H. Streeter, Merck Shsrp & Dohme .
1339
METABOLLSM OF PROBENECm
Vol. 9, No. 23
TABLE 1 Thin Layer Chromatography ead Melting Poiate of Probeaecid Metabolites M.P.
Ca~mpound
SS Ia ~
SS IIb
Found
Reference
PAG
0 .1
0 .1
A (aec . hydro~)
0 .46
0 .46
196-8
194-Z (1)
B (carbo~)
0 .54
0 .61
203-5
203-4(3)
C (prim. hydro~)
0 .36
N-depropyl
0 .58
0 .61
212-14
2114-15c
Probeaecid
O .qO
0 .~4
194-6
eSS I = benzene ethyl acetate :acetic acid (7 :3 :1) . bSS II = benzene : acetic acid (2 :1) . cMelting point obtained with authentic compound kindly provided by Di. J . M . Sprague, Merck Sharp & Dahme ; Guariao et al. (1) reported 207-90 . The pathways of metabolism of probenecid in maa are indicated in Figure 1. 0
c-o-Rw SlNi-n , ~!N!-n COON ~ClN,-~ tR
~ClX,-~
~RORERECIO
COON
COON
ÇOOX
COON O1N
CX=CN:CN=ON f0~`~ ! T N -n ! !
~ .CN=CN=COON f0R ! ~ClX,-n
~CNECN-CR! f0=11 ~C lX,-~
FIG . 1 Biotreasformatioa of Probeaecid in Mea . Structures of Metabolites .
fO=~ - ClNl-n
METAHOLI3M OF PROBENECm
1340
Vol . 9, No. 23
Assay of metabolites were made by quantitative extraction of urinary 14C with ethyl acetate follwed by thin-layer chromatography .
One cm sections of
silica gel were added to the cocktail, shaken and allowed to settle in the darà for one hour prior to counting . ed alongside the urinary extracts .
Appropriate standards were chromatographThe pattern of urinary excretion for the
metabolites is given in Table 2 . TABLE 2 Pattern of Urinary Excreti m of Probenecid Metabolites in Two Normal Human Subjects, (2g P .O. - 10 uc) x Dose as 14C excreted in urine Subject I Subject II 0_24 hr. 24-48 hr. 0-24 hr_ 24-48 hr. 2 .9 1 .1 2,8 0 .7
Compound Probenecid PAG
21
20
31
11
A
9 .6
2 .9
6 .1
1.1
B
6 .5
2 .7
5 .4
0.9
C
2.9
G.8
1 .3
0 .3
N-depropyl
5 .6
2 .4
3 .8
0.8
A & N-depropyl conjugates
2 .0
1 .4
3 .0
1 .1
The material left at the origin after thin-layer chromatography of h>mzan urine extracts was subjected to hydrolysis by refluxiag with 4N H2S04. Measurements of the resulting P thus obtained were made by quantitative thin Dyer"chromatography ; good agreement was demonstrated with values determined from the same aliquots with a modified hydroxamate assay previously shown to be specific for PAG (4) .
A small additional amoumt of metabolites A sad
N-depropyl (the s>.>m ranged from 3 .4z to 4,1x in 48 hrs) were also produced by hydrolysis .
Similar studies using ß-glucuronidase (Ketodase) at pH's 5 .0 and
6 .5 were also done with material from the origin .
At pH 5,0, which is optimum
vol. 9, No. 23
METABOLISM OF PROHENECiD
1341
for ß-ether glucuronidea, essentially no metabolites xere released and mlY a moderate amount of P xas liberated.
At pH 6 .5, (optimal for hydrolysis of
ß-aryl glucuronidesZ,both the large amounts of P sad the relativie proportions of metabolites A and N-depropyl xere the same as obtained xith treatment xith 4N H2S01~ .
We conclude that the material at the origin coasiats of PAG and a
small amount of metabolites A ~ad N-depropyl is the form of ß-acyl glucuronides .
Plasma concentrations of the side chain metabolites xere
relatively low (Table 3), indicating rapid renal clearance . TABLE 3 Pattern of Plasma Concentrations of Probenecid and Metabolites at Various Periods Plasma Concentrat ons mg/1 Time (hr) Subject I
Subject II
Probenecid
PAG
Swa of A, B, C and N-depropyl
4
89
3.1
1 .5
8
102
8.9
5 .k
24
43
5 .4
1,8
1.1
0 .1
3
9 .T
6
58
4.4
0,2
10
40
7.2
0.3
0,3
0.l
27
6 .3
Dis cuSssioa These results indicate species differences in the metabolism of P betxeen man and rat .
The major urinary metabolite found is man is PAG (41-42f is 48
hours), xhereae Guarino and associates (1) did no+. find it in bile Pram renal ligated Sprague-Daxley rats .
Theae . authors indicated that 64x of the biliary
radioactivity can be accounted for as conjugated metabolites, mainly in the
1942
METAHOLISM OF PROHENECiD
form of ß-ether gluctiranides .
Vol . 9, No . 29
The pattern of urinary excretion of P in man
shoos that the sum of metabolites A, B, C and N-depropyl account for moat of the remainder of the dose, the amount of unchanged P excreted being small (3.5 to 4 .Ox in 48 hours) .
Thus, the combined excretion of these metabolites
approximate the amount of PAG excreted .
The urinary metabolites described
above are present in the free form, except for a small quantity of conjugated A sad N-depropyl .
Since the metabolism of P is men has been shown to be dose-
dependent (5), it is quite possible that the pattern of urinary excretion and plasma concentration of the metabolites could be different et lower doses than at 2 .0 g ; such e study would be indicated. Ia the two subjects, the stmt of B sad C is about the same as the excretion of A (Table 2) .
Furthermore, much more B than C is present in urine .
The
above fYadings lead to the possibility that a common intermediate such es an epoxide might be formed, which upon ring opening, leads to equivalent amotmts of both the terminal (C) sad secondary (A) alcoholic metabolites ; since eloahol dehydrogeaase has e greater affinity for a terminal hydroxy (6), C would subsequently be more rapidly oxidized to the corresponding acid (H) . The present investigation end the results reported by Guarino and associates (1), suggest that in man, the microsomal oxidative pathway is equally important as glucturoaidation (formation of PAG), whereas in the rat, the conjugatian to ß-ether glucuranides prevail .
However, with respect to
the biliary excretion of the rat, some points need flu~ther elucidatian .
The
data ae given (1) shored that about 64x of administered 14C-P was excreted in the bile as conjugates, while after treatment with ß-glucuronidase at pH 4 .5, only a total of 40~ ores accotmted for as metabolites A, B, C and A-depropyl. The rest of the fraction released by enzymatic hydrolysis was unchanged P. Additional studies are needed to determine whether this apparent discrepancy (about 24x of the dose) is due to the presence of PAG in rat bile and whether PAG is also excreted in rat urine .
In this connection, the presently describ-
ed quantitative thin-layer chromatographic methods have proven to be more than
Vol . 9, No . 23
METAHOLLSM OF PROHENECm
1343
adequate for quantitativa of probenecid metabolism . At present, further investigations of the pharmacological properties of the metabolites are being undertaken in relation to our interest in structureactivity relationships (7) in the probenecid series . Summary The metabolic fate of probenecid (p-(dipropyleulfamayl) benzoic acid) in man hen been elucidated by determining the chemical structures of the urinary metabolites and their pattern of excretion.
The methodology included mainly
the utilization of quantitative thin-layer chromatography sad the data iras confirmed by GLC-LE .
Substantiating our previous findings, in 48 hrs about
402 of the dose is eliminated ea probenecid monoacyl glucureaide, trhile ezcretion of the uncheaged drug is small (ti42) .
The other metabolic products
result from oxidative attack of the n-prapyl side chain and are the monohydro~lated derivatives at the secondary (7 .22-12 .52), terminal (1 .6x-3 .7Z) positions, and the earbaagr (6 .32-9 .22), A-depropyl (4 .62-8 .02) compounds . These metabolites are excreted mostly in the free form, a small smouat of the secondary hydro~gr and the A-depropylated drugs (3 .42) being present probably es ß-aryl glucuronides .
Apparently, species differences in the metabolic dis-
position of probenecid are evident, since previous rat biliary excretion studies had reported the absence of the aryl glucuroaide of probenecid and that the other metabolites are fotimd mostly as ß-ether glucuraaides .
The
possibility that the ozidized metabolites are formed from a ca~oa intermediate is discussed. 1. 2. 3. 4. 5. 6. 7.
References A. M. GUARINO, W. D. COPWAY and H . M. FALES, Evrop . J . PhA~~,^.. 8, 244 (1969) . J. M. FEREL, A. B. GUTMAN, T . F . YU sad P . G. DAYTON . Clin. . Rea . 18 342 (1970) . R. F. CU9NINGHAM, P. G. DAYTON sad J . . M. PEREL, Unpublished observations . J. M. PEREL, T. F. YÎJ, A. B. GUTMAN sad P . G . DAYTON . Submitted to Pharmacol. Clin . P. G. DAYTON, 8 . A. CUCINELL, M. WEISS sad J . M. PEREL, J. Pharmac. Ezp. Ther . ~, 305 (1967) . F. LUND~ûIST, Alcohols and derivatives, is International Ea cl die of Pharmacol and Ther sauts ~(Ed . J .Tremolieres . Pergemaa Press, Oxford 1970 . P . G~ DAYTON, M. WEISS and J. M. PEREL, J . Med. Chem. Q,941 (1966) .
Pergamon Press
IDENTIFICATION AND RENAL EXCRETION OF PROBENECID MLTABOLITEB IN MANf James M. Perel, Robert F . Cunaiaghem, Henry M. Fales and Peter G. Dayton Depts . of Medicine (Clinical Pharmacology) end Gàemietry Emory University School of Medicine, Emory University, Atlaata,Ga . 30322 sad Molecular Diseases Breach, National Heart and Luag Institute, NIH, Betheada, Maryland 20014 U . S. A.
(Received 28 August 1970; in find form 8 October 1970)
Recently Guarino et all;(1) have reported the identification of several metabolites of probenecid (P)+ from rat bile .
Similarly, our experiments++
with ring l4 C probenecid in man, indicate that only a Fraction of the radio activity in urine could be accounted for as unchanged P and as probenecid aryl mono-glucuronide(PAG) (2) .
The present report deals with the identifi-
cation and qusatitation of essentially all the metabolites found is the urine of subjects receiving probenecid . Methods and Results Two normal subjects xere administered 2 g of P es a single oral dose (2g of P end 10 Nc of 14C-P were dissolved is ethanol sad evaporated to dryness) . Fractional urine collectiaae were stored in the presence of toluene (1 ml/1) and 50x acetic acid (20 ml/1) ; heparinized plasma was stored at -200. biological material was acidified xith
lOZ
of its volume of
extracted txice with two times its volume of ethyl acetate .
6
The
N HC1 sad
The eztract wes
brought to dryness in vacuo at 350 , the residue xes dissolved in ethanol end applied to silica gel G (Merck) plates sad chrcmatographed in solvent system I, benzene : ethyl acetate : acetic acid (7 :3 :1) .
Mesa spectrometric and gas
a Thia work xas supported in part by Grant CM 142g0 from the National Institute of General Medical Sciences, National Institutes of Health . }; Due to typographical error, the mass spectra of Metabolites A and C were inverted in this paper. + Probenç cid = HenemidR . ++ The 14C-P xas a gift from Dr . J. E . Beer, Merck Sharp b Dohme, West Point, Penasylveaia .
1337
METAHOLISM OF PROHENECiD
1338
Yol . 9, No. 23
chromatographic techniques were the same as previously described (1) . 14 C was counted in ea LS 250 Bechaa liquid scintillation spectrometer . tillation cocktail was prepared as follows :
to 1 L of toluene,
The scin
7
g of PPO,
0 .36 g POPOP end 200 ml Bio-Soly BB3-3 (Beckman) were added . The nomenclature and structures deacribèà in this report are the same es those used previously (1) end are the follwing : Metabolite A,p-(N-propyl, N-2-hydroxyprapylsulfamoyl) benzoic acid ; Metabolite B, p-(N-propyl, N-2 carbo~grethylsulfamoyl) benzoic acid4
Metabolite C, p-(N-propyl, N-3-hydroxy-
propyleulfamoyl) benzoic acid ; R-depropyl metabolite, p-(propylsulfamoyl) benzoic acid .
Metabolites A}, B and the R-depropyl metabolite were obtained
in crystalline form by removing appropriate silica gel areas off thin-layer plates and extracting with ethyl acetate .
After repeating the chromatographic
end extractive procedures, the oily residue which resulted upon evaporation to dryness, was dissolved is a minimum volume of ethanol, treated with charcoal sad crystallized twice from ethanol-water. niques, metabolite C was only obtained as an oil.
Using the same techTable 1 lists the melting
polst canateate end the relative chromatographic mobilitiee of the metabolitee~ PAG and P in two different solvent systems. Ia addition to gas chromatographic sad mass spectrometric cheracterization .of each metabolite, the N-depropyl metabolite and A were also compared with authentic materials on thin-layer chromatography sad with mined melting point determinations .
The carbon, hydrogen and nitrogen analysis}a of
metabolite H gave the following results : Calcd. for H, 5.43 ; N,
+
4.44 .
Ç13H17N06S :
C, 49 .524
Found: C, 49 .10 ; H, 5.40 ; N, 4 .20.
Isolated Metabolite A was found to be in the racemic form . Elemental analysis obtained through the courtesy of Mr .Kermit H. Streeter, Merck Shsrp & Dohme .
1339
METABOLLSM OF PROBENECm
Vol. 9, No. 23
TABLE 1 Thin Layer Chromatography ead Melting Poiate of Probeaecid Metabolites M.P.
Ca~mpound
SS Ia ~
SS IIb
Found
Reference
PAG
0 .1
0 .1
A (aec . hydro~)
0 .46
0 .46
196-8
194-Z (1)
B (carbo~)
0 .54
0 .61
203-5
203-4(3)
C (prim. hydro~)
0 .36
N-depropyl
0 .58
0 .61
212-14
2114-15c
Probeaecid
O .qO
0 .~4
194-6
eSS I = benzene ethyl acetate :acetic acid (7 :3 :1) . bSS II = benzene : acetic acid (2 :1) . cMelting point obtained with authentic compound kindly provided by Di. J . M . Sprague, Merck Sharp & Dahme ; Guariao et al. (1) reported 207-90 . The pathways of metabolism of probenecid in maa are indicated in Figure 1. 0
c-o-Rw SlNi-n , ~!N!-n COON ~ClN,-~ tR
~ClX,-~
~RORERECIO
COON
COON
ÇOOX
COON O1N
CX=CN:CN=ON f0~`~ ! T N -n ! !
~ .CN=CN=COON f0R ! ~ClX,-n
~CNECN-CR! f0=11 ~C lX,-~
FIG . 1 Biotreasformatioa of Probeaecid in Mea . Structures of Metabolites .
fO=~ - ClNl-n
METAHOLI3M OF PROBENECm
1340
Vol . 9, No. 23
Assay of metabolites were made by quantitative extraction of urinary 14C with ethyl acetate follwed by thin-layer chromatography .
One cm sections of
silica gel were added to the cocktail, shaken and allowed to settle in the darà for one hour prior to counting . ed alongside the urinary extracts .
Appropriate standards were chromatographThe pattern of urinary excretion for the
metabolites is given in Table 2 . TABLE 2 Pattern of Urinary Excreti m of Probenecid Metabolites in Two Normal Human Subjects, (2g P .O. - 10 uc) x Dose as 14C excreted in urine Subject I Subject II 0_24 hr. 24-48 hr. 0-24 hr_ 24-48 hr. 2 .9 1 .1 2,8 0 .7
Compound Probenecid PAG
21
20
31
11
A
9 .6
2 .9
6 .1
1.1
B
6 .5
2 .7
5 .4
0.9
C
2.9
G.8
1 .3
0 .3
N-depropyl
5 .6
2 .4
3 .8
0.8
A & N-depropyl conjugates
2 .0
1 .4
3 .0
1 .1
The material left at the origin after thin-layer chromatography of h>mzan urine extracts was subjected to hydrolysis by refluxiag with 4N H2S04. Measurements of the resulting P thus obtained were made by quantitative thin Dyer"chromatography ; good agreement was demonstrated with values determined from the same aliquots with a modified hydroxamate assay previously shown to be specific for PAG (4) .
A small additional amoumt of metabolites A sad
N-depropyl (the s>.>m ranged from 3 .4z to 4,1x in 48 hrs) were also produced by hydrolysis .
Similar studies using ß-glucuronidase (Ketodase) at pH's 5 .0 and
6 .5 were also done with material from the origin .
At pH 5,0, which is optimum
vol. 9, No. 23
METABOLISM OF PROHENECiD
1341
for ß-ether glucuronidea, essentially no metabolites xere released and mlY a moderate amount of P xas liberated.
At pH 6 .5, (optimal for hydrolysis of
ß-aryl glucuronidesZ,both the large amounts of P sad the relativie proportions of metabolites A and N-depropyl xere the same as obtained xith treatment xith 4N H2S01~ .
We conclude that the material at the origin coasiats of PAG and a
small amount of metabolites A ~ad N-depropyl is the form of ß-acyl glucuronides .
Plasma concentrations of the side chain metabolites xere
relatively low (Table 3), indicating rapid renal clearance . TABLE 3 Pattern of Plasma Concentrations of Probenecid and Metabolites at Various Periods Plasma Concentrat ons mg/1 Time (hr) Subject I
Subject II
Probenecid
PAG
Swa of A, B, C and N-depropyl
4
89
3.1
1 .5
8
102
8.9
5 .k
24
43
5 .4
1,8
1.1
0 .1
3
9 .T
6
58
4.4
0,2
10
40
7.2
0.3
0,3
0.l
27
6 .3
Dis cuSssioa These results indicate species differences in the metabolism of P betxeen man and rat .
The major urinary metabolite found is man is PAG (41-42f is 48
hours), xhereae Guarino and associates (1) did no+. find it in bile Pram renal ligated Sprague-Daxley rats .
Theae . authors indicated that 64x of the biliary
radioactivity can be accounted for as conjugated metabolites, mainly in the
1942
METAHOLISM OF PROHENECiD
form of ß-ether gluctiranides .
Vol . 9, No . 29
The pattern of urinary excretion of P in man
shoos that the sum of metabolites A, B, C and N-depropyl account for moat of the remainder of the dose, the amount of unchanged P excreted being small (3.5 to 4 .Ox in 48 hours) .
Thus, the combined excretion of these metabolites
approximate the amount of PAG excreted .
The urinary metabolites described
above are present in the free form, except for a small quantity of conjugated A sad N-depropyl .
Since the metabolism of P is men has been shown to be dose-
dependent (5), it is quite possible that the pattern of urinary excretion and plasma concentration of the metabolites could be different et lower doses than at 2 .0 g ; such e study would be indicated. Ia the two subjects, the stmt of B sad C is about the same as the excretion of A (Table 2) .
Furthermore, much more B than C is present in urine .
The
above fYadings lead to the possibility that a common intermediate such es an epoxide might be formed, which upon ring opening, leads to equivalent amotmts of both the terminal (C) sad secondary (A) alcoholic metabolites ; since eloahol dehydrogeaase has e greater affinity for a terminal hydroxy (6), C would subsequently be more rapidly oxidized to the corresponding acid (H) . The present investigation end the results reported by Guarino and associates (1), suggest that in man, the microsomal oxidative pathway is equally important as glucturoaidation (formation of PAG), whereas in the rat, the conjugatian to ß-ether glucuranides prevail .
However, with respect to
the biliary excretion of the rat, some points need flu~ther elucidatian .
The
data ae given (1) shored that about 64x of administered 14C-P was excreted in the bile as conjugates, while after treatment with ß-glucuronidase at pH 4 .5, only a total of 40~ ores accotmted for as metabolites A, B, C and A-depropyl. The rest of the fraction released by enzymatic hydrolysis was unchanged P. Additional studies are needed to determine whether this apparent discrepancy (about 24x of the dose) is due to the presence of PAG in rat bile and whether PAG is also excreted in rat urine .
In this connection, the presently describ-
ed quantitative thin-layer chromatographic methods have proven to be more than
Vol . 9, No . 23
METAHOLLSM OF PROHENECm
1343
adequate for quantitativa of probenecid metabolism . At present, further investigations of the pharmacological properties of the metabolites are being undertaken in relation to our interest in structureactivity relationships (7) in the probenecid series . Summary The metabolic fate of probenecid (p-(dipropyleulfamayl) benzoic acid) in man hen been elucidated by determining the chemical structures of the urinary metabolites and their pattern of excretion.
The methodology included mainly
the utilization of quantitative thin-layer chromatography sad the data iras confirmed by GLC-LE .
Substantiating our previous findings, in 48 hrs about
402 of the dose is eliminated ea probenecid monoacyl glucureaide, trhile ezcretion of the uncheaged drug is small (ti42) .
The other metabolic products
result from oxidative attack of the n-prapyl side chain and are the monohydro~lated derivatives at the secondary (7 .22-12 .52), terminal (1 .6x-3 .7Z) positions, and the earbaagr (6 .32-9 .22), A-depropyl (4 .62-8 .02) compounds . These metabolites are excreted mostly in the free form, a small smouat of the secondary hydro~gr and the A-depropylated drugs (3 .42) being present probably es ß-aryl glucuronides .
Apparently, species differences in the metabolic dis-
position of probenecid are evident, since previous rat biliary excretion studies had reported the absence of the aryl glucuroaide of probenecid and that the other metabolites are fotimd mostly as ß-ether glucuraaides .
The
possibility that the ozidized metabolites are formed from a ca~oa intermediate is discussed. 1. 2. 3. 4. 5. 6. 7.
References A. M. GUARINO, W. D. COPWAY and H . M. FALES, Evrop . J . PhA~~,^.. 8, 244 (1969) . J. M. FEREL, A. B. GUTMAN, T . F . YU sad P . G. DAYTON . Clin. . Rea . 18 342 (1970) . R. F. CU9NINGHAM, P. G. DAYTON sad J . . M. PEREL, Unpublished observations . J. M. PEREL, T. F. YÎJ, A. B. GUTMAN sad P . G . DAYTON . Submitted to Pharmacol. Clin . P. G. DAYTON, 8 . A. CUCINELL, M. WEISS sad J . M. PEREL, J. Pharmac. Ezp. Ther . ~, 305 (1967) . F. LUND~ûIST, Alcohols and derivatives, is International Ea cl die of Pharmacol and Ther sauts ~(Ed . J .Tremolieres . Pergemaa Press, Oxford 1970 . P . G~ DAYTON, M. WEISS and J. M. PEREL, J . Med. Chem. Q,941 (1966) .