m. anthony j. glazko§ and maxwell finland...

PERSISTENCEOF ANTIBIOTICS IN BLOODOF PATIENTS WITHACUTERENALFAILURE. II. CHLORAMPHENICOLAND

ITS METABOLICPRODUCTSIN THE BLOODOF PA-TIENTS WITH SEVERERENALDISEASE OR

HEPATIC CIRRHOSIS * t

By CALVIN M. KUNIN,t ANTHONYJ. GLAZKO§ AND MAXWELLFINLAND

(From the Thorndike Memorial Laboratory, Second and Fourth (Harvard) Medical Services,Boston City Hospital, and the Department of Medicine, Harvard Medical School,

Boston, Mass., and from the Research Division, Parke, Davis and Company,Detroit, Mich.)

(Submitted for publication April 7, 1959; accepted May 1, 1959)

lt is known that the kidney plays a major butvariable role in the elimination of most of theantibiotics that are used systemically. Since thesedrugs are often employed in the prevention andtreatment of infections in patients with severerenal disease, it becomes essential, both for thechoice of agents and for their most effective use, toknow how the different antibiotics are handled bythe patient with impaired renal function. Thepresent series of studies was therefore under-taken with a view to providing a basis for therational choice of antibiotics and their dosage insuch patients. The persistence of several othercommonly used antibiotics in the blood of pa-tients with anuria and severe renal impairmentwas described in other papers of this series (2, 3).This paper is concerned with the overall metabo-lism of chloramphenicol in similar patients. Inaddition, since the liver is also involved in themetabolism of chloramphenicol, studies in a fewpatients with severe hepatic cirrhosis are alsoincluded.

The structure of chloramphenicol and possiblesites of chemical alterations as they occur in thebody are shown in Figure 1. A summary ofwhat is currently known about the metabolism ofchloramphenicol in man is presented schematicallyin Figure 2. Following the adminstration of chlor-

*Aided in part by a grant (E-23) from the UnitedStates Public Health Service.

t An abstract of this paper has been published (1).t Postdoctorate Fellow, National Institute of Allergy

and Infectious Diseases. Present address: Department ofPreventive Medicine, University of Virginia, Charlottes-ville, Va.

§ Biochemist, Research Division, Parke, Davis andCompany.

amphenicol by the oral or parenteral route, 75 to90 per cent of the administered dose may berecovered in the urine of patients who have normalrenal function (4, 5). From 5 to 15 per cent ofthe recovered drug is in the microbially activeform; the remainder is composed largely of aninactive monoglucuronide conjugate and to alesser extent products of hydrolysis (6). Arylamine derivatives of chloramphenicol are not ordi-narily detectable in the serum or urine of man.About 3 per cent of the administered dose ofchloramphenicol is excreted into the bile (4, 7)but less than 1 per cent is recoverable in thefeces, largely as aryl nitro and amine derivatives(4).

In sharp contrast to the situation in man, theprinciple pathway of excretion of chloramphenicolin the rat is by the biliary system (8). Whenthe drug reaches the intestine of the rat, the glu-curonide linkage is hydrolyzed by the action ofthe bacterial flora, regenerating chloramphenicol(9). The nitro group may also be reduced to anamine (9) which is partially reabsorbed and ex-creted into the urine (8). Up to 25 per cent ofthe administered dose may be recovered in theurine of rats as inactive aryl nitro and aminederivatives.

In the present study, the half-life of chlor-amphenicol in serum and the 24 hour urinaryrecovery of chloramphenicol and its metabolicproducts were determined following single intra-venous injections of the drug. These valueswere used to compare the fate of chloramphenicolin patients with renal and hepatic disease with thatin normal subjects.

1498

ANTIBIOTICS IN RENAL FAILURE. II. CHLORAMPHENICOL

MATERIALS AND METHODS

Patients studied and drugs used. The patients in whomthese studies were made include four who were anuric, 11who had varying degrees of renal impairment but normalliver function, 11 with nutritional (mostly alcoholic)cirrhosis of the liver but without significantly reducedrenal function and four normal subjects. The levels ofchloramphenicol and its derivatives were determined inthe serum of six additional anuric patients who hadbeen receiving chloramphenicol therapeutically. Forpurposes of the present study, anuria is defined as thecondition in which a uremic patient excretes less than400 ml. of urine daily for three or more days. It wasassumed that the creatinine clearance in anuric patientswas less than 1 ml. per minute. The diagnosis of cirrho-sis of the liver was based on clinical and laboratoryfindings and in many of the patients was confirmed byliver biopsy.

Chloramphenicol 1 was supplied for intravenous usein ampules containing 500 mg. dissolved in 2 ml. of a50 per cent aqueous solution of N,N-dimethylacetamide.The contents of one vial was diluted to 150 ml. in 5per cent aqueous solution of dextrose and injected intra-venously over a period of 15 to 20 minutes. Venousblood for the assays was drawn before and two hours af-ter the injection and at convenient intervals thereafter; atleast five specimens were obtained following eachinjection.

Assays for chloramphenicol and its derivatives. Theconcentration of antimicrobially active chloramphenicol inthe serum and urine was determined by a turbidimetricassay using a strain of Shigella sonnei (10). Most of thecontrol sera from jaundiced patients, however, were foundto inhibit this organism; such sera were, therefore, as-sayed by the same method using Agrobacterium tume-faciens which was not inhibited by control sera. The con-centration of total nitro compounds plus amines was de-termined by the titanous chloride reduction procedure

1 Supplied by Parke, Davis and Company as Chloromy-ceting solution.

HYDROLYSIS

CH HN-GO0- CHCI2I I

__ ~~I IpN O w-O -CH20H

REDUCTIONTO OH H GLUCURCARYL AMINE LINKA

ONIDEAGE

FIG. 1. SITES OF METABOLIC ALTERATIONS IN STRUC-TURE OF CHLORAMPHENICOL

(11); the aryl amines were determined on the same fil-trates by the method of Bratton and Marshall (12) andthe concentration of nitro compounds was calculated bythe difference. All results are expressed in terms ofchloramphenicol equivalents.

Identification of chloramphenicol and its products.Chloramphenicol glucuronide was identified in urine andin serum filtrates by paper chromatography using thedescending procedure with butanol-phenol-pyridine sol-vent described elsewhere (6). The urine was applieddirectly to the paper strips; the serum was first deprotein-ized with five volumes of ethanol, centrifuged, and thesupernatant concentrated by evaporation at room tem-perature. A known sample of chloramphenicol glucuro-nide (6) was used for comparison of Rf values; thepresence of this compound in the unknown samples wasconfirmed by the addition of f-glucuronidase which re-sulted in the regeneration of microbially active chloram-phenicol. After chromotography, the location of thearyl nitro compounds on the paper strips was estab-lished by reduction with titanous chloride, bromination,diazotization and coupling (6).

The following terms are therefore used in this paperto describe chloramphenicol and its metabolic derivatives:1) Microbially active chloramphenicol, as determined inthe turbidimetric assays; 2) Aryl amine derivatives, in-dicating the value determined by the Bratton-Marshallmethod; and 3) Total nitro compounds, which includesthe microbially active drug plus the inactive nitro deriva-tives.

Calculations of half-life and clearances. The serum

ACTIVE CHLORAMPHENICOL

Liver,? Other Sites

5-15% in Urine

MONOGLUCURONIDE+ PRODUCTSOF HYDROLYSIS f 75-90% in Urine

Via Bile (<3%)Action ofI ntestinalBacteria

14?ARYL AMINE ANDARYL NITRO DERIVATIVES Trace Resorbed

and Excreted

<1% IN FECES

FIG. 2. METABOLISMOF CHLORAMPHENICOLIN NORMALMAN

1499

CALVIN M. KUNIN, ANTHONYJ. GLAZKOAND MAXWELLFINLAND

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half-life (T/2) was calculated by the method of leastsquares (13). The degree of renal impairment wasestimated from the 24 hour endogenous creatinine clear-ance (Ccr) (14), a modification of the method of Bonsnesand Taussky (15) being used to determine the concen-tration of creatinine in serum and urine.

Dialysis by the Kolff-coil artificial kidney was per-formed for therapeutic purposes in three anuric patients,the extraction ratio (ER) of creatinine and chlorampheni-col being determined as in the previous paper (3).

RESULTS

Anuric patients

Table I presents data on four anuric patientsand four normal subjects who were given a doseof chloramphenicol intravenously. The half-lifeof the microbially active drug in the serum ofanuric patients does not differ greatly from thatobserved in the the normal subjects. In con-trast, the serum half-life of the nitro compoundsis markedly prolonged in the anuric patients overthat found in the normals. In addition, arylamines which are usually < 5 ,g. per ml. in se-

> rum of patients with normal renal function, were(U(Uc present in the anuric patients at levels rangingco

.. from 4 to 31 Mg. per ml. and persisted for long*~ periods. It is not known whether this is due to0o drug metabolites or to the presence of other sub-0 stances.

Figure 3A presents the serum levels of theactive and total nitro compounds as determined

= in the four normal subjects following an intra-*> venous injection of chloramphenicol. The peak; levels of either component at two hours after the.a intravenous injection did not exceed 8 pg. per._a ml. and at 24 hours little or none was demon-

.ed strable in the serum; aryl amines were not de--4

4J tectable. Figure 3B shows the serum levels ind> an anuric patient who received an intravenousX.0 6 injection of the same amount of drug. The micro-

' bially active component reached about the samelevels at two hours and disappeared at about thesame rate as in the normal subjects. The total

r. nitro derivatives, however, rose to a level of 28^*s M,ug. per ml. at six hours and then declined slowly,

S.. Q but were still detectable at 120 hours. The level-.d g of aryl amines was slightly elevated prior to

< treatment and rose steadily to 11 pg. per ml.>=t (chloramphenicol equivalent) at 120 hours.

The latter patient had received procaine penicil-

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PATIENT: J1, 43 YRS., POSTHEMOLYTICCRISIS

*-. TOTAL NITRO

X-K ARYL AMINES

.-- -- ACTIVE

0-0 10 20 30 40 50 60 70 80 90 100 110 120

HOURS AFTER INTRAVENOUS DOSE OF 500 MG.

FIG. 3. MEANLEVELS OF CHLORAMPHENICOLAND ITS METABOLIC PRODUCTSIN SERUMA) Four patients with normal renal function, and B) an anuric patient after a

single intravenous dose of 500 mg. of chloramphenicol.

fin for several days up to 18 days prior to thisstudy; the possibility was therefore consideredthat this might have accounted for the finding ofaryl amines in this patient's serum prior to theadministration of the chloramphenicol. In orderto obtain further data on this possibility and alsoto determine whether uremia per se could giverise to substances in the serum that react likearyl amines in the Bratton-Marshall method,sera were obtained from 12 uremic patients whohad not received chloramphenicol. Levels of arylamines, equivalent to 1 to 38 jug. of chlorampheni-col per ml. were demonstrated in these sera. Inmost of these patients, however, there was ahistory of administration of some drug whichgave a positive test for amines such as procaine(usually as procaine penicillin) or chlorothiazide.Previous administration of other aryl amines thatare diazotized in this method, such as sulfona-mides, acetazolamide and para-aminobenzoic acid,could not be excluded in all cases and many ofthese patients had minor surgical procedures dur-ing which procaine was injected. For thesereasons, additional sera were obtained from sevenuremic patients (nonprotein nitrogen values rang-ing from 63 to 165 mg. per 100 ml.) in whom

previous administration of such substances coulddefinitely be excluded. In most of these sera thelevel of aryl amines was less than 1.0 jug. per ml.and the highest value was 1.5 Mug. per ml. It wastherefore concluded that the finding of aryl aminesin the blood of the uremic patients usually re-sulted from the administration of substances con-taining this moiety and their retention in theblood.

Patients uitli varying degrees of renal impair-ment

The mean half-life of active chloramphenicoland of the total nitro compounds was calculatedfor 11 patients with varying degrees of renal im-pairment. These data together with those ofTable I are presented and correlated with thecreatinine clearances in Figure 4. The serumhalf-life of the microbially active compound wasnot greatly altered by the severity of the renaldisease as reflected in the level of creatinine clear-ance. On the other hand, the half-life of thetotal nitro compounds was prolonged when thecreatinine clearance fell below 20 ml. per minute.In many of the uremic patients, the peak levels ofnitro compounds in the serum was not reached

1501


ANURIC

PATIEN *

NONANURIC

PATIENT

NITRO DERIVATIVE

MICROBIALLY ACTIVE

NITRO DERIVATIVE

MICROBIALLY ACTIVE

II

II I I I I T

20 30 40 50 60 70 80 90CREATININE CLEARANCE (ML/MIN)

FIG. 4. HALF-LIFE OF MICROBIALLY ACTIVE CHLORAMPHENICOLANDOF TOTAL NITROCOMPOUNDSAS RELATEDTO CREATININE CLEARANCEIN THE SERUMOF PATIENTS WITH

NORMALRENAL FUNCTION AND IN THOSE WITH VARYING DEGREES OF RENALIMPAIRMENT

until five to 10 hours after administration of thedrug; the reason for this was not determined,but it may be due to a difference in the relativevolume distribution of chloramphenicol and itsmonoglucuronide. It has been shown that chlor-amphenicol is concentrated in tissues, whereas theglucuronide is water soluble and presumably is

distributed in the extracellular water (4, 16).

Accumulation of chloramphenicol in the blood ofpatients on continuous therapy

The results presented above suggest that activechloramphenicol given in ordinary doses is inac-tivated nearly as rapidly in patients with severe

renal failure as in normal individuals, but that in

the former the total nitro compounds may ac-

TABLE II

Levels of chloramphenicol and its derivatives in anuric patients receiving chloramphenicol for therapeutic purposes

Chloramphenicol in serum

Days of Total Aryl TotalPatient Age Sex Etiology of renal failure treatment dose Active amine nitro

yrs. Gm. g./mi. pg./mt. g9/mI.Sa. 26 M Acute hemorrhagic pancreatitis 2 4.0 13 50St. 32 F Premature separation of placenta 3 6.0 11.9 158

10 20.0 10.2 47 611K. 17 M Ethylene glycol intoxication 7 8.5 23.0 40 333W. 83 F Postoperative 9 13.0 13.1 189T. 68 M Bladder perforation, shock 14 13.0 12.3 31 134F. 47 M Acute glomerulonephritis 8 16.0 <2.5 28 50

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1502


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I I I I I I I I I I I I ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~5 I I1 2 3 4 5 6 7 8 9 10 l1 12 13 14 15 16 17 18 19 20

D A Y S

FIG. 5. LEVELS OF CHLORAMPHENICOLAND ITS METABOLIC PRODUCTSOBTAINED INTHE SERUMOF A PATIENT DURING THE DIURETIC PHASE FOLLOWINGA PERIOD OFANURIA IN THE COURSEOF WHICHSHE HAD BEEN TREATEDWITH CHLORAMPHENICOLORALLY

cumulate to very high levels. This is borne out bythe data presented in Table II which shows theserum levels obtained during chloramphenicol ther-apy in six anuric patients. The highest level ofactive drug observed in this group was 23 Mtg. per

ml. in a patient who had been treated for seven

days, whereas the highest level of the total nitrocompounds and aryl amine derivatives noted in Pa-

tient St. were 611 and 47 ,Mg. per ml., respectively.The latter patient was in the diuretic phase of re-

covery and was no longer receiving the drug atthe time the highest serum level was noted. Thefall of chloramphenicol levels following cessationof therapy in this patient is illustrated in Figure5; although the active drug was rapidly clearedfrom the serum, the total nitro compounds and the

TABLE III

Extraction of chloramphenicol and creatinine by the artificial kidney

Chloramphenicol* Creatinine

Extraction ExtractionPatient Arterial Venous ratio (A) Arterial Venous ratio (B) A/B X100

;'g./m1. tg./ml. % mg. % mg. % % %Se (a) 44 37 16 22.0 15.2 31 52

(b) 39 34 13 18.9 13.4 29 44

Pe 7 4 43 22.0 5.0 77 56

Ta (a) 131 (22) 90 (17.6) 31(20) 25.8 9.0 65 48 (31)(b) 103 (18.2) 100 (15.0) 3 (18) 17.4 8.4 52 6 (35)

Mean 21 (19) 51 (59) 41 (33)

* Total nitro compounds were determined Colormetrically. Data for the active chlorampheniCol is shown inparentheses,

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1503


PATIENTS PATIENTSWITHOUT WITH

LIVER LIVERDISEASE Di SEASE

10-HALF -LIFE

OF ACTIVE 8-

CHLORAMPHENICOL

IN SERUM

I(HO URS) ____ .

(SOLID AND INTERRUPTED *00 *LINES DENOTE MEAN 0 __2 STANDARDDEVIATIONS) 2 !

FIG. 6. HALF-LIFE OF MICROBIALLY ACTIVE CHLORAM-PHENICOL IN THE SERUMOF PATIENTS WITH AND WITH-OUT SEVERELIVER DISEASE

aryl amines were removed more slowly. Paperchromatograhpy of the serum that showed thehighest values for the total nitro compounds re-vealed that the major component had the sameRf as an authentic sample of chloramphenicolglucuronide.

Effect of hemodialysis with the artificial kidneyon chloramphenicol levels

Three anuric patients were subjected to hemodi-alysis by the artificial kidney (Kolff-coil type) fortherapeutic purposes. The results, expressed asextraction ratio of the drug compared with thatof creatinine, are presented in Table III. Therewas considerable variation in the extraction ratioof chloramphenicol and creatinine from one dialy-sis period to another. The comparative extrac-tion of chloramphenicol and creatinine indicatesthat the nitro compounds were diffusible acrossthe dialyzing membrane, but less so than creati-nine. This may reflect the degree of binding ofthe nitro compounds to constituents of blood (16,17). In general, the nitro compounds werecleared about half as well as creatinine and the

microbially active drug probably about one-thirdas well. There is no ready explanation for thelow extraction of total nitro compounds in thesecond series of observations in Patient Ta.

Effect of liver disease on the serum half-life andexcretion of chloramphenicol

Eleven patients, all of whom had advanced cir-rhosis of the liver, were each given 500 mg. ofchloramphenicol intravenously; three of these pa-tients had ascites and 10 had elevated levels ofserum bilirubin. The half-life of active chlor-amphenicol in.the serum of these 11 patients isshown in Figure 6; results of similar determina-tions in patients without cirrhosis of the liver, butwith varying degrees of renal impairment are alsoshown in this figure for comparison. The meanserum half-life of active chloramphenicol in thepatients without liver disease was 2.9 + 0.9 hours.Among the patients with cirrhosis, there weremarked differences in the serum half-life of theactive drug, but at least three of the 12 observa-tions showed a marked prolongation of the half-life over the normal values. The cirrhotic pa-tient with the lowest serum half-life was the onlyone who was not jaundiced. However, the cor-relation between the serum half-life of active chlor-amphenicol and the total bilirubin level was im-perfect; the correlation coefficient was + 0.54,significant at the 5 per cent level, suggesting thatfactors in severe liver disease other than totalbilirubin retention may be involved in the abnor-mal metabolism of chloramphenicol.

Table IV lists the total amounts of chlor-amphenical and its products recovered in theurine of six patients with hepatic cirrhosis duringthe 24 hours following intravenous administra-tion of 500 mg. of chloramphenicol. Chromato-graphic analysis demonstrated high concentrationsof glucuronide in these urines. Although threeof these patients had clearances of creatinine thatwere below normal, the overall recovery of thedrug was comparable to that reported for normalindividuals (4, 5); this was true for active chlor-amphenicol as well as for the total nitro com-pounds. The defect in chloramphenicol metabo-lism in the patients having the longer serum half-life of active chloramphenicol therefore appearsto be a reduced rate of conversion of active drug

1504


to inactive products rather than a reduction in thetotal amount of drug converted.

DISCUSSION

The data presented in this study on the per-

sistence of chloramphenicol and its metabolicproducts in the serum of patients with severe renalor hepatic disease confirm and extend observa-tions made in previous investigations in normalman (4, 5, 7). The observation that the serum

half-life of microbially active drug is not signifi-cantly prolonged in anuric patients indicates thatthe rate of removal of the drug by conversion toits metabolic products is virtually unaffected byrenal disease. The prolonged serum half-life andthe accumulation of the metabolic products inuremic patients imply that the rate of removalother than by renal mechanisms must be quiteslow; in anuric patients it probably proceeds atless than 1 per cent per hour.

The prolongation of the serum half-life of chlor-amphenicol metabolites as the creatinine clearancefalls is not as striking as that noted with tetra-cycline (3). This is presumably due to the factthat the chloramphenicol residues are cleared notonly by glomerular filtration, but by active tubu-lar secretion as well (4). Although there isgenerally a parallel decline in tubular function withfalling glomerular filtration rates in uremic pa-

tients (18), this may not be adequately reflectedin estimations of the glomerular filtration rate as

determined by the creatinine clearance. Theanuric patient, however, has a profound loss oftubular as well as glomerular functional capacity

which may explain the abrupt change in the half-life of the chloramphenicol products in anuricpatients as noted in Figure 4.

The study of chloramphenicol metabolism inpatients with liver disease was hampered by theunexpected inhibitory action of serum from jaun-diced patients on the test organism, Shigellasonnei. This was remedied, in part, by the use

of Agrobacterium tumefaciens which was less af-fected by these sera. Some of the patients withcirrhosis converted chloramphenicol to its met-abolic products more slowly than did normal or

uremic patients. Despite this somewhat slowerconversion rate as estimated by the decline in se-

rum of the active drug, about the same total andfractional amounts of chloramphenicol and itsproducts were recovered in~ the 24 hour urine col-lections. Since abundant chloramphenicol glu-curonide was recovered in these urines, it wouldappear that the patients with cirrhosis are ca-

pable of conjugating chloramphenicol. Thus, thedefect noted in these patients was in the rate ofconversion rather than in the total amount con-

verted. Similar results have been reported in pa-tients with liver disease given a salicylamide load(19). Such findings emphasize the need for de-termining the rate of glucuronide synthesis ratherthan the total amount synthesized.

From the data presented, it would appear thatone approach to achieving greater antibacterialactivity of chloramphenicol in blood or urinewould be to reduce the extent to which the drugis conjugated with glucuronic acid. N-acetyl-para-aminophenol (NAPA) has been reported tobe conjugated with glucuronic acid to a much

IE IV

Urinary recovery of chioramphenicol and its products in patients with hepatic cirrhosis during 24 hoursfollowing an intravenous dose of 500 mg.

Chloramphenicol in urine Recovered in urine

Total Aryl Total Aryl TotalPatient bilirubin Ccr Active amine* nitro Active amine nitro

mg. % ml./min. mg. mg. mg. % % %Hi 2.8 45.5 66 23 355 13.2 4.6 71.0Bu 4.4 76.0 39 16 325 7.7 3.2 65.0Da 0.3 82.0 78 25 433 15.7 5.0 86.6Wa 3.5 80.7 62 30 325 12.2 6.0 65.0St 1.8 103.1 71 32 417 14.3 6.4 83.4Mr 3.9 62.0 41 28 333 8.2 5.6 66.7

Mean 2.8 74.9 60 26 365 11.9 5.1 73.0

* Normal urinary amines are included in these determinations.

1505


greater extent than are salicylamide or acetyl-salicylic acid (20). Corte and Johnson (21)also have reported that the administration ofNAPA in doses of 250 mg. per Kg. to rabbitsgiven together with cortisol or prednisolone re-sulted in a marked increase in plasma levels of 17-hydroxycorticoids which, like many other sub-stances, are inactivated to a large extent by glu-curonide formation (22). In a preliminary briefstudy carried out in two normal subjects, theadministration of NAPA2 did not appear to in-fluence the metabolism of chloramphenicol to anysignificant degree. It is possible that more pro-longed therapy or larger doses of either or bothdrugs, as compared with those used in this trial,may be necessary before an effect of NAPAcanbe demonstrated. Schmid and Hammaker (23),however, have recently shown that prolonged ad-ministration of NAPA may actually augmentglucuronide production. In view of their findingsit may be very difficult to overcome the glucuroni-dization mechanism by this type of competitiveinhibition.

Chloramphenicol appears to be readily conju-gated with glucuronic acid. Even where indirectbilirubin levels are high, suggesting poor conju-gation of this substrate, large amounts of chlor-amphenicol glucuronide may be formed. It hasbeen reported that the cat does not form glucuro-nates of phenolic substrates such as borneol, men-thol, etc. (24). However, in other studies, oraladministration of chloramphenicol to the cat hasresulted in the excretion of large quantities of itsglucuronide in the urine (25). Similiar ex-periments carried out in these laboratories with astrain of rats (26) that had been found deficientin the glucuronic acid conjugating mechanism forbilirubin, gave chromatographic evidence for thepresence of chloramphenicol glucuronide in theurine following administration of chloramphenicol.'It is possible that the primary alcohol group aspresent in chloramphenicol is more readily con-jugated than phenolic compounds or bilirubin.

The aryl amine derivatives of chloramphenicolare ordinarily present in very low concentrationsin the serum or urine of patients under treatment

2 Supplied as Atasol, Frank Horner, Ltd., Montreal,Canada.

3We are indebted to Dr. Rudi Schmid for providingthe Gunn rats for this study.

(4). They appear gradually in the serum ofuremic patients. The presence of aryl amines inthe serum of uremic patients resulting from theadministration of chloramphenicol invites compari-sons with the situation in the rat in which largeamounts of the aryl amine derivatives are excretedinto the feces and urine. This has been shownto be the result of an active entero-hepato-renalcircuit in the rat where nitro derivatives are ex-creted into the bile, reduced by the enteric florato aryl amines and reabsorbed and excretedthrough the kidneys (8). Although in humans,only small amounts of chloramphenicol are ex-creted into the bile (4, 7), larger amounts mayeventually get into the bile when renal clearancesare markedly reduced. This may account for thegradual accumulation of aryl amine derivatives inthe blood of uremic patients. It is also possiblethat reduction of the nitro group may occur inorgans others than the gastrointestinal tract (4).

The accumulation of inactive chloramphenicolproducts in the blood of uremic patients raisesthe question of their potential toxicity for suchpatients. Chloramphenicol has been implicatedas a causative factor in some cases of aplasticanemia (27-32). Since uremic patients are usu-ally also anemic, further bone marrow depressionthat might result from chloramphenicol or itsproducts may be difficult to detect. Of interest inthis regard is a recent report of 15 patients ob-served during chloramphenicol administration inwhich five patients showed a reduced incorpora-tion of iron into hemoglobin on the basis of whichit was suggested that this drug may produce sub-clinical bone marrow depression (33). Althoughthe possible role of renal impairment in thesecases was not discussed, three of the five patientswere listed as having renal disease, and two ofthe remaining 10 who showed no adverse effectfrom chloramphenicol are also listed as havingsome disease of the kidney.

Evidence has accumulated that at and soon afterbirth there is a deficient glucuronide formingmechanism (34-38). There is also a reducedtubular and glomerular functional capacity (39,40) as compared with that of older children andadults. It would therefore be expected that bothchloramphenicol and its products would be re-moved from the blood more slowly in those in-fants than in older children (41).

1506


Dialysis by the artificial kidney has been shownto reduce serum levels of both chloramphenicoland its nitro derivatives. Removal of largeamounts of the drug by this method is hamperedby the fact that the total nitro compounds are re-moved only about one-half as well as creatinine andeven less of the active drug may be extracted.

Although the data on uremic patients indicatesthat normal dosage schedules must be used withchloramphenicol to maintain adequate therapeuticlevels, the accumulation of inactive metabolicproducts introduces a new factor that must beconsidered. Although chloramphenicol glucuro-nide appears to be less toxic than the parent com-pound. the potential toxicity of the aryl amines isunknown. The hazards of administration of anydrug to uremic patients must be recognized whenthe normal routes of elimination are unavailable.More serious results might be expected with com-pounds such as streptomycin which are normallyexcreted unchanged or with drugs whose metabolicproducts are more toxic than the original sub-stance.

In patients with known hepatic impairment theoverall metabolism of chloramphenicol appears tobe essentially normal even though the rate of con-jugation with glucuronic acid may be reduced.When renal function is adequate in cirrhotic pa-tients, the prolongation of serum half-life doesnot appear to be great enough to justify anychange from the usual dosage regimens.

SUMMARY

1. The serum half-life of active chloramphenicolis not significantly prolonged in anuric patients;on the other hand, the half-life of the metabolicproducts of chloramphenicol is markedly extendedin patients with severe renal disease.

2. Small amounts of aryl amine derivatives mayaccumulate slowly in the blood of uremic pa-tients receiving chloramphenicol.

3. Some patients with cirrhosis of the liverwere found to have a prolongation of the serumhalf-life of active chloramphenicol. This appearedto be due to a slower rate of glucuronide conjuga-tion in these patients.

4. Aryl nitro compounds of chloramphenicolwere found to be extracted by the artificial kidneyabout one-half as well as creatinine.

5. These findings are discussed in relation tothe potential toxicity of chloramphenicol productsin uremic patients and in regard to dosage in pa-tients with renal or hepatic disease.

ACKNOWLEDGMENT

The authors are indebted to Dr. John P. Merrill, PeterBent Brigham Hospital, for permission to study severalof his patients, including those subjected to hemodialysis,and for the creatinine determinations performed in hislaboratory. The helpful advice of Dr. Rudi Schmid isgratefully acknowledged. The colormetric assays w'ereperformed by Miss T. Kaczala and Mr. E. Thompson,and the microbial assays were done by Mrs. M. Gal-braith in the laboratories of Parke, Davis and Company.The creatinine determinations were done by Miss JudyCrouch.

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m. anthony j. glazko§ and maxwell finland...

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