Ciprofloxacin Decreases the Rate of Ethanol Elimination in Humans

Gut 1999;44:347–352 347 Ciproﬂoxacin decreases the rate of ethanol

elimination in humans Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from

J Tillonen, N Homann, M Rautio, H Jousimies-Somer, M Salaspuro

Abstract Liver catalase can oxidise ethanol in vitro, but Background—Extrahepatic ethanol me- under physiological conditions catalase ap- tabolism is postulated to take place via pears to play only a minor role in ethanol microbial oxidation in the colon, mediated metabolism.2 by aerobic and facultative anaerobic bac- Extrahepatic elimination of ethanol does, teria. however, also occur. To a smaller extent, etha- Aims—To evaluate the role of microbial nol is oxidised to acetaldehyde in other tissues ethanol oxidation in the total elimination possessing ADH activity, such as the stomach, rate of ethanol in humans by reducing gut small intestine, colon, kidneys, and lungs.4 In flora with ciprofloxacin. rats, the extrahepatic gastrointestinal metabo- Methods—Ethanol was administered in- lism of circulating ethanol has been shown to travenously at the beginning and end of a be up to 30% of that in the liver.5 Furthermore, one week period to eight male volunteers. in patients with cirrhosis of the liver, extrahe- Between ethanol doses volunteers re- patic elimination has been estimated to consti- ceived 750 mg ciprofloxacin twice daily. tute about 40% of the total ethanol 6 Results—A highly significant (p=0.001) elimination. reduction in the ethanol elimination rate Due to its high water solubility, ethanol lev- (EER) was detected after ciprofloxacin els inside the terminal ileum7 and colon8 are medication. Mean (SEM) EER was 107.0 equal to those of the blood. We have recently (5.3) and 96.9 (4.8) mg/kg/h before and shown in experimental animals that ethanol after ciprofloxacin, respectively. Faecal can be oxidised via the aerobic and facultative 9 Enterobacteriaceae and Enterococcus sp. anaerobic bacteria in the large intestine. Most were totally absent after medication, and of the luminal bacteria are anaerobic, and faecal acetaldehyde production capacity without oxygen they are capable of producing 10 was significantly (p<0.05) decreased from energy through fermentation. In alcoholic

0.91 (0.15) to 0.39 (0.08) nmol/min/mg fermentation the end product is ethanol, which http://gut.bmj.com/ protein. Mean faecal alcohol dehydroge- is derived from acetaldehyde in a reductive 11 nase (ADH) activity was significantly reaction mediated by bacterial ADH. How- (p<0.05) decreased after medication, but ever, oxygen diVuses through the colonic ciprofloxacin did not inhibit human he- mucosa, and, accordingly, the human gut con- patic ADH activity in vitro. tains a mucosa associated microflora in which the number of aerobic and facultative anaero- Conclusions—Ciprofloxacin treatment 12 decreased the ethanol elimination rate by bic bacteria is almost comparable to that of on September 25, 2021 by guest. Protected copyright. 9.4%, with a concomitant decrease in anaerobic bacteria. Under these conditions and intestinal aerobic and facultative anaero- in the presence of exogenous ethanol, the ADH bic bacteria, faecal ADH activity, and mediated bacterial reaction can oxidise ethanol acetaldehyde production. As ciprofloxacin to acetaldehyde in a reaction in which nicotinamide adenine dinucleotide (NAD) acts as an has no eVect on liver blood flow, hepatic 13 ADH activity, or cytochrome CYP2E1 electron acceptor. Microbial catalases, in the presence of H2O2, can also oxidise ethanol to activity, these eVects are probably caused 14 by the reduction in intestinal flora. acetaldehyde. Research Unit of (Gut 1999;44:347–352) Ciprofloxacin possesses excellent in vitro Alcohol Diseases, and in vivo antibacterial activities against most University of Helsinki, Keywords: ciprofloxacin; ethanol; colonic bacteria; aerobic and facultative anaerobic bacteria, Tukholmankatu 8 F, metabolism; alcohol dehydrogenase; acetaldehyde including Enterobacteriaceae.15 16 Further- 00290 Helsinki, Finland more, ciprofloxacin is partly eliminated J Tillonen 17 N Homann through the intestinal wall, and the concen- M Salaspuro The most important route of ethanol elimina- trations of ciprofloxacin in the faeces and tion is its metabolism in the liver, with small intestinal mucosa are higher than the corre- Anaerobe Reference amounts excreted in the breath (0.7%), urine sponding serum levels.18 This transintestinal Laboratory, National (0.3%), and sweat (0.1%).1 Three principal elimination pattern may explain the ability of Public Health hepatic enzyme systems are involved: alcohol this drug to modify the colonic flora. Institute, Helsinki, dehydrogenase (ADH), the microsomal etha- Treatment with ciprofloxacin was recently Finland 2 M Rautio nol oxidising system (MEOS), and catalase. It shown to reduce the rate of ethanol elimination H Jousimies-Somer is generally agreed that the major part of etha- by 9% in rats, and this was associated with a nol is metabolised by cytosolic ADH.2 The Correspondence to: contribution of the MEOS to ethanol elimina- Professor Salaspuro. Abbreviations used in this paper: ADH, alcohol tion is limited, and only a minor part (1–5%) of dehydrogenase; EER, ethanol elimination rate; GOX, Accepted for publication the total metabolism in vivo is carried out by glucose oxidase; MEOS, microsomal ethanol oxidising 23 September 1998 the cytochrome P450 dependent MEOS.3 system; NAD, nicotinamide adenine dinucleotide. 348 Tillonen, Homann, Rautio, et al

reduction in faecal aerobic flora and faecal Faecal samples were collected before and after ADH activity.19 The aim of the present study medication, and samples were frozen to −80°C was to evaluate the role of microbial ethanol within six hours. oxidation in the total elimination of ethanol in Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from man by reducing human gut flora with BACTERIAL ANALYSIS ciprofloxacin. The second aim was to study The faecal samples were thawed, and1gof possible changes in faecal flora and faecal each specimen was suspended and serially enzyme activities participating in both ethanol diluted (10-fold) from 10−1 to 10−6 in peptone oxidation and acetaldehyde production before yeast extract broth. Undiluted sample and a 10 and after administration of ciprofloxacin for µl aliquot of the appropriate dilutions were one week. inoculated and spread on several selective and non-selective agar media for the enumeration Materials and methods and isolation of total counts and main groups SUBJECTS of aerobic and anaerobic bacteria and yeasts. After approval by the Ethical Committee at the The aerobic plates were incubated at 35°Cin

University Central Hospital of Helsinki, eight an atmosphere containing 5% CO2 for up to healthy men, with an age range of 21–31 years ﬁve days; anaerobic plates were incubated in participated in the in vivo studies. Mean body anaerobic jars ﬁlled with the evacuation

weight was 78 (3) kg, and body mass index replacement method with mixed gas (90% N2, 2 23.8 (0.4) kg/m . None of the subjects had 5% CO2,5%H2) for seven days for the first received any antibiotics for four weeks preced- inspection and up to 14 days for the final ing the study or was using any other drugs dur- inspection. The sensitivity of this method was ing the study days. One of the subjects was a 3000 colony forming units (cfu)/g faeces. The light smoker. All were moderate consumers of bacteria were enumerated and identified by alcohol, with a weekly average consumption of established methods.20 21 70 g or less of ethanol. All participants were told to refrain from ethanol for at least 36 hours FAECAL ACETALDEHYDE PRODUCTION before the study. To measure acetaldehyde production capacity, faecal samples were lyophilised for 24 hours STUDY DESIGN (Micromodulyo 1.5K Freeze Dryer, RV5 A paired design in which each subject served as Rotatory Vane Pump, Edwards High Vacuum his own control was used (open, non- Int., UK). Thereafter dried faecal samples were randomised, no placebo control). Two study dissolved in 0.1 M potassium phosphate days were separated by a one week interval. (KPO) buVer (pH 7.4) at a concentration of 20 The volunteers were admitted to the University mg/ml. To obtain supernatant, the solution was Central Hospital of Helsinki, and all studies first homogenised (10 × 5 seconds, 1200 min−1; http://gut.bmj.com/ started between 8 00 and 9 00 am. Two intra- Potter S Homogenizer, B. Braun Melsungen venous lines (Viggo, 1.22 mm/18GL32mm, AG, Germany) and then sonicated (8 × 20 sec- BOC Ohmeda AB, Helsingborg, Sweden) were onds, 20 kHz, Sonics & Materials, USA), placed into the antecubital veins at the surrounded by ice to avoid protein coagulation. beginning of each study day, one for the This was followed by centrifugation of the administration of ethanol and one for obtaining sonicate at 100 000 g at 5°C for 60 minutes, repeated blood samples. Ethanol (0.63 g/kg and supernatant was collected and used for

body weight) was mixed in 5% glucose solution measurements. A 250 µl aliquot of supernatant on September 25, 2021 by guest. Protected copyright. at 7% concentration and was administered at a was incubated for 60 minutes in closed glass constant rate over a 30 minute period intrave- vials with 50 µl ethanol/buVer mixture (final nously. This application was chosen to avoid concentration 22 mM ethanol, 0.1 M KPO the influence of the first pass metabolism and buVer, pH 7.4) at 37°C after adding diVerent alterations in gastric motility on ethanol coenzymes. The coenzymes used were nicoti- pharmacokinetics. Eating and smoking were namide adenine dinucleotide (NAD; final con- prohibited during the study. Blood samples (3 centration in the reaction mixture 3 mM) to ml) were taken into vacutainer tubes contain- activate ADH, glucose oxidase (GOX; final ing 0.06 ml EDTA for measurement of blood concentration 0.03 µmol/min) and glucose alcohol levels by head space gas chromatogra- (final concentration 10 mM) to produce

phy. Baseline samples were taken before hydrogen peroxide (H2O2) and to activate cata- ethanol administration had started (time 0) lase, or both. All the reagents were obtained and at five minute intervals during the first from Sigma Chemical Co. (St Louis, Missouri, hour, at 15 minute intervals during the second USA). Reactions were stopped by injecting 50 hour, and at 20 minute intervals until the µl of 6 mol/l perchloric acid (PCA) through the breath ethanol analyser (Lion Laboratories, rubber septum of the vial; the final volume in Barry, UK) showed no detectable blood vials was 500 µl. Acetaldehyde was analysed ethanol levels. The protocol was exactly the using headspace gas chromatography as de- same on both study days. During the seven scribed previously.22 To control for non- days between the experiments, the volunteers enzymatic artefactual acetaldehyde formation received 750 mg ciprofloxacin (Ciproxin, Bayer from ethanol during the protein precipitation,23 AG, Leverkusen, Germany) orally twice a day. PCA was added simultaneously with ethanol The drug intake was started on the evening of into additional incubation vials (incubation the first infusion day and the last tablet was time 0) and the revealed values were subtracted taken one hour prior to the administration of from acetaldehyde values obtained after the intravenous ethanol on the second study day. 60 minute incubation period. Acetaldehyde Ciprofloxacin decreases ethanol elimination in humans 349

Table 1 EVects of ciproﬂoxacin on ethanol pharmacokinetics after the absorption and distribution of the dose is completed. The y intercept of the Before CIP After CIP p Value regression line (C0) is the concentration of Peak ethanol (mM) 22.47 (1.00) 23.27 (1.26) NS ethanol in blood if the dose of 0.63 g/kg was Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from V (l/kg) 0.70 (0.02) 0.70 (0.02) NS d distributed into total body water immediately C0 (mM) 19.68 (0.54) 19.71 (0.58) NS EER (mg/kg/h) 107.0 (5.3) 96.9 (4.8) 0.001 after the infusion started. The ratio of dose of AUC (mM/h) 58.9 (2.9) 65.5 (3.3) 0.0004 ethanol (g/kg) divided by the parameter C0 is Time 0 (h) 5.99 (0.31) 6.61 (0.32) 0.0003 the apparent volume of distribution of ethanol

Results expressed as mean (SEM). (Vd). The ethanol elimination rate (EER) from CIP, ciprofloxacin. the body was obtained by dividing the dose given (0.63 g/kg) by the estimated time of production was related to the protein concen- reaching zero concentration of ethanol in blood tration of the supernatant determined by the (time ). The time parameter corresponds to method of Lowry et al.24 0 0 the x intercept of the concentration-time regression equation. The areas under the FAECAL ENZYME ACTIVITIES concentration-time profiles (AUCs) were To measure ethanol oxidising enzymes, ADH determined by the trapezoidal method from and catalase, supernatant, prepared as above, the beginning of ethanol administration to the was used. ADH activity of the supernatant was time when it was no longer detectable. determined spectrophotometrically by following the reduction of NAD (final concentration 3 mM in 0.1 M KPO, pH 7.4) using 25 mM or STATISTICAL ANALYSIS 1.5 M ethanol (in KPO) at 37°C. Catalase The results are expressed as mean (SEM). The activity of the supernatant was determined statistical significance of the diVerences before spectrophotometrically at 240 nm after the and after the ciprofloxacin intake was analysed ° by Student’s paired test. A p value of less than addition of 10 mM H2O2 at 37 C (in 0.1 M t KPO, pH 7.4).25 Enzyme activities were related 0.05 was considered to be significant. The pos- to the protein concentrations of the superna- sible correlations were tested by using simple tant. linear regression analysis.

HEPATIC ADH ACTIVITY Human liver tissue was obtained from a patient Results undergoing surgery. Liver tissue was first EFFECT OF CIPROFLOXACIN ON ETHANOL homogenised in the ratio of 1:4 (in 0.1 M PHARMACOKINETICS KPO, pH 7.4) The homogenate was then cen- Figure 1 represents the mean (SEM) values of trifuged at 1000 g at 4°C for 10 minutes, the concentration-time profiles of ethanol in followed by centrifugation at 100 000 g at 5°C blood and regression lines to the elimination http://gut.bmj.com/ for 60 minutes to obtain cytosol. Cytosolic phase of the curves for eight subjects. Table 1 ADH activity was determined spectrophoto- summarises the pharmacokinetic parameters metrically by following the reduction of NAD of ethanol derived from blood concentration− (final concentration 3 mM in 0.1 M KPO, pH time data. The time to reach zero ethanol con-

7.4) using 25 mM ethanol (in KPO). The centration in blood (time0) increased after cip- eVect of ciprofloxacin on ADH activity was rofloxacin medication, and accordingly there tested by adding increasing drug concentra- was a highly significant decrease (p=0.001) in on September 25, 2021 by guest. Protected copyright. tions (final concentrations 1, 10, 20 µg/l) to the the EER. The mean (SEM) ethanol elimina- buVer used. tion rates were 107.0 (5.3) mg/kg/h before the ciprofloxacin treatment and 96.9 (4.8) mg/kg/h PHARMACOKINETICS OF ETHANOL IN BLOOD after treatment for one week. The overall The concentration-time profiles of ethanol decrease in EER was 9.4%. The individual rate were evaluated according to zero order kinet- of ethanol elimination decreased in all volun- ics. This pharmacokinetic model assumes a teers (fig 2). The highest decrease in EER was rectilinear disappearance of ethanol from blood 17.6% and the lowest 5.1%.

25 Before ciprofloxacin After ciprofloxacin 20

20 15 * 15 * * * * ** * 10 ** *** 10 *** * ** Ethanol (mM) * Ethanol (mM) ** * * * 5 5 * * * *

0 0 0 100 200 300 400 500 600 0 50 100 150 200 250 300 350 400 Time (minutes) Time (minutes)

Figure 1 Blood ethanol concentrations (mean (SEM)) before and after ciproﬂoxacin treatment. *p<0.05, **p<0.001, ***p<0.0001. 350 Tillonen, Homann, Rautio, et al

140 Before ciprofloxacin cfu/g in two subjects out of eight after After ciprofloxacin ciprofloxacin administration. The total count 130 of anaerobic bacteria declined slightly. This was mainly due to a drop in the number of Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from 120 Bifidobacterium sp., initially present in six subjects, and present after ciprofloxacin ad- 110 ministration in three of eight subjects. Table 2 summarises the bacteriological results for the 100 faecal samples.

90 EFFECT OF CIPROFLOXACIN ON FAECAL ENZYMES AND ACETALDEHYDE PRODUCTION 80 The mean ADH activity of the faecal samples

Ethanol elimination rate (mg/kg/h) measured before ciprofloxacin treatment was 70 significantly (p<0.05) higher at both ethanol Figure 2 The eVect of ciprofloxacin treatment (750 mg concentrations than that of the samples taken twice a day) for seven days on individual ethanol elimination rates in eight volunteers. after treatment (table 3). The high ethanol concentration was used in order to saturate all Table 2 EVects of ciprofloxacin on faecal bacteriological microbial ADH isoenzymes. The catalase counts activity, however, remained unchanged after Before CIP After CIP ciprofloxacin dosing (table 3). The acetaldehyde production capacity of the faecal samples Anaerobes also decreased significantly after ciprofloxacin Total counts 3.5 × 10−9 6.9 × 10−8 Bifidobacterium sp. 4.3 × 10−8 2.6 × 10−4 treatment when NAD was used as a cofactor to B fragilis-gr 3.8 × 10−8 3.2 × 10−8 activate ADH, but remained unaltered when −5 −4 Clostridium sp. 6.2 × 10 8.9 × 10 glucose + glucose oxidase was used to activate Aerobes Total count 1.1 × 10−8 6.5 × 10−6 catalase (table 4). Enterobacteriaceae 1.0 × 10−8 0 Ciprofloxacin did not have any significant in Enterococcus sp. 1.2 × 10−6 0 −6 −4 vitro e ect on the activity of human hepatic Streptococcus sp. 1.2 × 10 5.1 × 10 V Staphylococcus sp. 1.3 × 10−3 8.8 × 10−4 ADH at the concentrations used. ADH activity Lactobacillus sp. 4.9 × 10−6 6.1 × 10−6 was 100.3%, 98.9%, and 102.5% compared × −6 × −4 Corynebacterium sp. 1.5 10 1.0 10 with the control samples without the drug, Results expressed as mean cfu/g (n=8). when 1, 10, and 20 µg/l (final concentrations) CIP, ciprofloxacin. of ciprofloxacin, respectively, were used. Although the individual rate of ethanol EFFECT OF CIPROFLOXACIN ON FAECAL BACTERIA elimination decreased in all subjects, no corre- Ciprofloxacin treatment for seven days pro- lation could be found between the decrease in http://gut.bmj.com/ duced a clear decline in the number of faecal the individual EERs and the reduction in bac- aerobic bacteria from 1.1 × 108 cfu/g to 6.5 × 6 terial counts. On the other hand, there was a 10 cfu/g (p=0.04, Wilcoxon signed rank test). statistically significant positive correlation Before drug intake, Enterobacteriaceae was the (r=0.75, p<0.001) between faecal ADH activ- predominant aerobic flora present in every vol- ity at 1.5 M ethanol and acetaldehyde produc- unteer. Enterococcus sp. were found in five of the tion from ethanol.

eight subjects. After ciprofloxacin these species on September 25, 2021 by guest. Protected copyright. totally disappeared from the stool samples. Discussion Streptococcus sp. were initially present in five This study shows that treatment with cipro- subjects, Staphylococcus sp. in one, Lactobacillus floxacin for one week reduces the ethanol sp. in three, and Corynebacterium sp. in four elimination rate in man by 9.4% without subjects. These bacteria responded variably, aVecting the apparent volume of distribution. either disappearing in some cases, persisting in The intravenous administration of ethanol others, or even arising after medication. Yeasts excludes the possible eVects of altered gastric were not originally present in any volunteer, emptying and gastric first pass metabolism on × 4 × 4 but appeared at levels of 1.0 10 and 6 10 ethanol pharmacokinetics.26 Ciprofloxacin did Table 3 EVects of ciprofloxacin on faecal enzyme activities not inhibit hepatic ADH activity in vitro in concentrations exceeding serum concen- Before CIP After CIP p Value trations18 known to exist in the liver tissue dur- 27 ADH (25 mM) 1.17 (0.31) 0.47 (0.12) 0.013 ing treatment. Ciprofloxacin has, however, ADH (1.5 M) 2.98 (0.28) 1.28 (0.17) 0.006 been reported to reduce the hepatic metabo- Catalase 75.42 (8.97) 56.56 (8.76) NS lism of coadministered xanthines, such as Enzyme activities expressed as nmol NADH/min/mg protein for ADH; nmol/min/mg protein for theophylline and caVeine, leading to increased catalase. serum concentrations and reduced elimination CIP, ciprofloxacin. of these substances.28 The mechanism behind Table 4 EVect of ciprofloxacin on faecal acetaldehyde production this eVect has been suggested to be the specific inhibition of CYP1A2 activity.29 In addition, Before CIP After CIP p Value ciprofloxacin decreases cytochrome CYP3A4 After the addition of NAD 0.91 (0.15) 0.39 (0.08) 0.007 mediated biotransformation, but it does not After the addition of GOX 0.35 (0.06) 0.35 (0.05) NS inhibit the metabolism of substrates that are After the addition of both 0.94 (0.14) 0.57 (0.06) 0.044 specific for the CYP2E1 and CYP4A1 30 Results expressed as nmol/min/mg protein. isoenzymes. The isoenzyme CYP2E1 is the CIP, ciprofloxacin. major contributor to the MEOS in humans, Ciprofloxacin decreases ethanol elimination in humans 351

although CYP1A2 has also been considered to This is the first study to show that human play a role.31 Thus the inhibitory eVect of stool samples possess ADH and catalase activi- ciprofloxacin on the ethanol elimination rate ties and produce acetaldehyde from ethanol in could at least partly be the consequence of the vitro. The faecal ADH activity and acetalde- Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from drug’s interference with cytochrome mediated hyde production capacity decreased signifi- ethanol oxidation. The contribution of the cantly after ciprofloxacin treatment for one MEOS to ethanol metabolism, however, is at week, whereas catalase activity remained unal- most 5%.3 Hence it is obvious that possible tered. Furthermore, there was a significant interactions between ciprofloxacin and ethanol correlation between faecal ADH activity and oxidising enzymes in the liver can explain only acetaldehyde production. These results a small part of the reduction in the ethanol strongly suggest that ethanol oxidation by elimination rate. Hepatic metabolism of etha- colonic bacteria in man is mainly due to ADH nol may also be reduced because of the changes associated reactions. in hepatic blood flow. Ciprofloxacin, however, Jokelainen et al recently reported a 9% has no eVect on the clearance of indocyanine (p<0.02) reduction in ethanol elimination in green, a dye highly extracted by the liver, which rats after high dose ciprofloxacin treatment for indicates a lack of eVect on hepatic blood four days, with a concomitant decrease in fae- flow.32 Thus the decrease in ethanol elimination cal aerobic bacteria and ADH activity; yet an found in this study is unlikely to be the result of acute intraperitoneal dose of ciprofloxacin 60 minutes prior to ethanol administration had no decreased hepatic blood flow. 19 It has been shown in earlier experiments that eVect on the rate of ethanol elimination. This human colonic contents are capable of produc- implies that ciprofloxacin itself and/or its ing significant amounts of acetaldehyde when metabolites have no eVect on the hepatic clear- incubated with ethanol concentrations known ance of ethanol in vivo in rats. Neither were rat hepatic ADH nor MEOS activities a ected by to exist in the colon during social drinking.22 V the ciprofloxacin treatment. This animal study Furthermore, many aerobic Gram negative supports our present findings regarding hu- bacteria belonging to the family Enterobacte- mans. In contrast, another human study with riaceae and representing normal colonic flora ciprofloxacin (500 mg twice a day for three in man possess notable NAD dependent ADH days) showed no eVect on ethanol pharmacoki- activity, and are able to produce significant netics (AUC, EER, peak ethanol concentra- amounts of acetaldehyde when incubated in 38 33 tion) after an oral ethanol dose of 0.38 g/kg. vitro with ethanol. In vivo microbially derived In that study, as well in the present one, the last ethanol oxidation and acetaldehyde production dose of ciprofloxacin was taken one hour prior have been shown to occur in rats with a self fill- to the administration of ethanol. The explana- ing diverticulum and concomitant bacterial tion for these contradictory findings could be 34 35 http://gut.bmj.com/ overgrowth, and in the colon of pigs. These the notable interindividual variations (±20%) findings strongly suggest that intestinal mi- in ethanol elimination rates. In order to crobes are able to oxidise ethanol by a eliminate the eVects of this variation we used a bacteriocolonic pathway for ethanol study design in which each volunteer served as 93536 oxidation. his own control. This enables detection of The results of this study suggest that the small diVerences in EER that might be hidden decrease in ethanol elimination produced by in a placebo controlled study if the sample size

ciprofloxacin is most probably due to the is too small. An additional explanation is that in on September 25, 2021 by guest. Protected copyright. reduction in gut aerobic flora and the conse- the earlier study the dosage of the drug was quent inhibition of ethanol oxidation via lower and the duration of medication shorter colonic bacteria. The findings from the bacte- than in our study. Accordingly, it is possible riological analysis support this hypothesis. The that the elimination of colonic flora was not species of the family Enterobacteriaceae, which suYcient to reach the rate limiting threshold has been shown to possess ADH activity and to for bacterial ethanol oxidation. Due to a higher produce acetaldehyde from ethanol in vitro,33 ciprofloxacin dose we cannot entirely rule out disappeared from the stool after ciprofloxacin the possibility that other factors, such as inter- treatment. Also, Enterococcus species were actions with cytochrome enzymes, might also absent after medication. The bacterial flora of have influenced the results. the human large intestine forms an extremely Bacterial ethanol oxidation is a novel finding complex ecosystem, and there is almost never and of interest for the field of gastroenterology. empty territory in the gut. When one compart- It has been shown previously that intracoloni- ment of this ecosystem is disturbed, other bac- cally formed acetaldehyde is only poorly terial strains grow and fill this bare area. As can metabolised by colonic mucosa,39 40 and been seen in this study, the number of Lactoba- bacteria41 and that it can also be transported to cillus species, which have been shown to be able the liver via portal circulation.42 There is to metabolise ethanol to acetaldehyde poorly,37, evidence that a low dose of acetaldehyde deliv- were unchanged. In addition, the number of ered to rats in drinking water produces micro- Staphylococcus species were even more numer- vesicular fatty infiltration of the liver even in the ous after the medication. The growth of other absence of ethanol.42 Accordingly, acetalde- aerobic microbes that are not capable of hyde of extrahepatic origin (formed by bacte- ethanol oxidation probably makes it impossible rial ADHs from ethanol in the colon), may to find any correlations between the decrease in contribute to the pathogenesis of alcoholic liver the individual EERs and the reduction in total disease. Furthermore, intracolonically formed bacterial counts. acetaldehyde may increase intestinal 352 Tillonen, Homann, Rautio, et al

permeability,43 and chronic alcoholism may 19 Jokelainen K, Nosova T, Koivisto T, et al. Inhibition of bac- 44 teriocolonic pathway for ethanol oxidation by ciprofloxacin alter the composition of gut flora. These fac- in rats. Life Sci 1997;61:1755–62. tors may lead to elevated blood endotoxin 20 Summanen P, Baron EJ, Citron DM, et al. Wadsworth levels45 and may thereby contribute to the anaerobic bacteriology manual. 5th edn. Belmont, California: Gut: first published as 10.1136/gut.44.3.347 on 1 March 1999. Downloaded from 46 47 Star Publishing, 1993. pathogenesis of alcoholic liver disease, sug- 21 Murray PR, Baron EJ, Pfaller MA, et al,eds.Manual of clini- gesting the use of antibiotics in the treatment of cal microbiology. 6th edn. Washington DC: ASM Press, 1995. such disease. Nevertheless, we cannot exclude 22 Jokelainen K, Roine RP, Väänänen H, et al. In vitro the possibility that the bacteriocolonic pathway acetaldehyde formation by human colonic bacteria. 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