AMPICILLIN LEVELS IN HUMAN BILE

Updates on Antibiotic Regimens in Acute Cholecystitis

Acute cholecystitis is one of the most common surgical diseases, which may progress from mild to severe cases. When combined with bacteremia, the mortality rate of acute cholecystitis reaches up to 10-20%. The standard of care in patients with acute cholecystitis is early laparoscopic cholecystectomy. Percutaneous cholecystostomy or endoscopic procedures are alternative treatments in selective cases. Nevertheless, antibiotic therapy plays a key role in preventing surgical complications and limiting the systemic inflammatory response, especially in patients with moderate to severe cholecystitis. Patients with acute cholecystitis have a bile bacterial colonization rate of 35-60%. The most frequently isolated microorganisms are Escherichia coli, Klebsiella spp., Streptococcus spp., Enterococcus spp., and Clostridium spp. Early empirical antimicrobial therapy along with source control of infection is the cornerstone for a successful treatment. In these cases, the choice of antibiotic must be made considering some factors (e.g., the severity of the clinical manifestations, the onset of the infection if acquired in hospital or in the community, the penetration of the drug into the bile, and any drug resistance). Furthermore, therapy must be modified based on bile cultures in cases of severe cholecystitis. Antibiotic stewardship is the key to the correct management of bile-related infections. It is necessary to be aware of the appropriate therapeutic scheme and its precise duration. The appropriate use of antibiotic agents is crucial and should be integrated into good clinical practice and standards of care.

Antibiotics in the Biliary Tract: A Review of the Pharmacokinetics and Clinical Outcomes of Antibiotics Penetrating the Bile and Gallbladder Wall

Biliary tract infections (BTIs), including cholangitis and cholecystitis, are common causes of bacteremia. Bacteremic BTIs are associated with a mortality rate of 9-12%. The extent to which antibiotics are excreted in the bile and the ratio of their exposure to the minimum inhibitory concentration of the infecting organism are among the important factors for the treatment of BTIs. This review updates health care professionals on the distribution of antibiotics in the common bile duct, gallbladder, and gallbladder wall. Antibiotic efficacy in treating BTIs based on the latest available clinical studies is also discussed. The efficacy and pharmacokinetics of 50 antibiotics are discussed. Overall, most antibiotic classes exhibit biliary penetration that translates into clinical efficacy. Only seven antibiotics (amoxicillin, cefadroxil, cefoxitin, ertapenem, gentamicin, amikacin, and trimethoprim/sulfamethoxazole) had poor biliary penetration profiles. Three antibiotics (ceftibuten, ceftolozane/tazobactam, and doripenem) had positive clinical outcomes despite the lack of pharmacokinetic studies on their penetration into the biliary tract. Conflicting efficacy data were reported for ampicillin despite adequate biliary penetration, whereas conflicting pharmacokinetic data were reported with cefaclor and moxifloxacin. Even in the absence of supportive clinical studies, antibiotics with good biliary penetration profiles may have a place in the treatment of BTIs.

Drug monitoring in nonconventional biological fluids and matrices

Determination of the concentration of drugs and metabolites in biological fluids or matrices other than blood or urine (most commonly used in laboratory testing) may be of interest in certain areas of drug concentration monitoring. Saliva is the only fluid which can be used successfully as a substitute for blood in therapeutic drug monitoring, while an individual's past history of medication, compliance and drug abuse, can be obtained from drug analysis of the hair or nails. Drug concentrations in the bile and faeces can account for excretion of drugs and metabolites other than by the renal route. Furthermore, it is important that certain matrices (tears, nails, cerebrospinal fluid, bronchial secretions, peritoneal fluid and interstitial fluid) are analysed, as these may reveal the presence of a drug at the site of action; others (fetal blood, amniotic fluid and breast milk) are useful for determining fetal and perinatal exposure to drugs. Finally, drug monitoring in fluids such as cervical mucus and seminal fluid can be associated with morpho-physiological modifications and genotoxic effects. Drug concentration measurement in nonconventional matrices and fluids, although sometimes expensive and difficult to carry out, should therefore be considered for inclusion in studies of the pharmacokinetics and pharmacodynamics of new drugs.

Cefoperazone compared with ampicillin plus tobramycin for severe biliary tract infections

In a prospective, randomized, multicenter study, the efficacy and safety of cefoperazone and the combination ampicillin-tobramycin as initial therapy for patients with severe acute biliary tract infections were compared. Of 77 patients initially entered in the study, definite severe biliary tract infection was confirmed in 67. Sixty-four patients completed treatment. At the end of treatment, 35 of 36 (97%) patients given cefoperazone and 23 of 28 (82%) given ampicillin-tobramycin were cured of their infection (P = 0.07). Pathogens were recovered from the bile in 32 patients; microbiological cures were observed in 18 of 19 (94%) patients receiving cefoperazone and 8 of 13 (62%) receiving ampicillin-tobramycin (P = 0.03). Thirteen patients had septicemia. None (0%) of the eight septicemic patients from the cefoperazone group, but two of five (40%) from the ampicillin-tobramycin group, were clinical failures. Of the isolated pathogens, 51% were resistant to ampicillin, while the resistance rate was 4% for tobramycin and 1% for cefoperazone (P less than 0.001). Biliary concentrations of cefoperazone were maintained at high levels--236 +/- 87 micrograms/ml up to 12 h after administration. Even in the presence of severe obstruction, cefoperazone levels in the bile and gallbladder wall were above MICs for most pathogens. Cefoperazone may be considered as an excellent alternative in the therapy of severe biliary tract infections.

Biliary excretion of amoxycillin and ceftriaxone after intravenous administration in man

1 Plasma and biliary concentrations of amoxycillin and ceftriaxone were measured after bolus intravenous administration (500 mg) in four subjects with normal hepato-biliary and renal function. 2 The mean plasma elimination half-life for ceftriaxone (t 1/2 = 330 +/- 30 min) was considerably longer than that for amoxycillin (t 1/2 = 60 +/- 9 min). 3 The biliary concentration of ceftriaxone was above plasma concentration of the drug throughout the study period, whereas amoxycillin concentration in the bile was lower than that in plasma. 4 Both plasma and biliary concentrations of ceftriaxone were substantially higher than previously determined minimum inhibitory concentration (MIC) values for E. coli (and several other common biliary tract pathogens) for over 6 h following drug administration. Amoxycillin concentration in plasma fell below MIC by 2 h, and did not reach inhibitory concentrations in bile.

Biliary excretion of drugs in man

Biliary excretion is an important route for the elimination of some drugs and drug metabolites in man. The factors which determine elimination via the biliary tract include characteristics of the drug such as chemical structure, polarity and molecular size as well as characteristics of the liver such as specific active transport sites within the liver cell membranes. A drug excreted in bile may be reabsorbed from the gastrointestinal tract or a drug conjugate may be hydrolysed by gut bacteria, liberating original drug which can be returned to the general circulation. Enterohepatic circulation may prolong the pharmacological effect of certain drugs and drug metabolites, but the quantitative importance of this in man appears to be less than in animals. Biliary elimination may play a role in the interindividual differences in drug response observed in healthy subjects and in patients with certain diseases. Cholestatic disease states, in which normal bile flow is reduced, will influence drug elimination by this route resulting in increased risk of drug toxicity. Bile may serve as an alternate route of elimination in renal failure, but this has not been determined in man. Lack of reliable information regarding the biliary excretion of drugs in man is partly due to the relative inaccessibility of the human biliary tract. Most studies of drug excretion in human bile have been performed in post-surgical patients with T-tube drainage. This method of bile collection is not ideal because bile flow and composition are often severely altered during the period of study, not all bile is collected and enterohepatic circulation is partially interrupted. Recent advances in the methods of collection of bile may improve future studies of drug excretion in human bile.

Prophylactic use of cephazolin against wound sepsis after cholecystectomy

A trial of antibiotic prophylaxis with cephazolin against postoperative wound sepsis was carried out on 201 patients undergoing routine cholecystectomy. Wound sepsis occurred in 11 out of 65 controls (16.9%), who were not given the drug; two out of 63 patients (3.2%) given a single dose preoperatively; and four out of 73 patients (5.5%) given the single preoperative dose plus a five-day course postoperatively. The difference between the controls and patients given the single preoperative dose was significant.

Comparative biliary concentrations of cephazolin and cephalothin in patients with biliary tract disease

The concentration of cephazolin in the serum, gall bladder bile, common duct bile, and gall bladder wall were consideredably higher than cephalothin especially with IV administration and indicate that cephazolin should be a useful antibiotic in the surgical treatment of acute cholecystitis.

Biliary tract excretion of cefazolin, cephalothin, and cephaloridine in the presence of biliary tract disease

The biliary tract excretion of three cephalosporins, cefazolin, cephaloridine, and cephalothin, was compared in patients with biliary tract disease. In the absence of obstruction, mean antibiotic levels in bile from gall bladder and common duct in patients undergoing cholecystectomy were highest for cefazolin (17 and 31 mug/ml, respectively) than either cephaloridine (7 and 9 mug/ml) or cephalothin (1 and 4 mug/ml). Biliary tract levels generally paralleled serum levels. In no patient with cystic duct obstruction were any of the cephalosporins detectable in appreciable amounts in gall bladder bile. In patients with T-tube drainage given each of the three different cephalosporins on separate days, concentrations of cefazolin in bile were many-fold higher than either cephaloridine or cephalothin. Peak levels of cefazolin in T-tube bile averaged 51 mug/ml after intravenous and 26 mug/ml after intramuscular administration, whereas mean peak levels of cephalothin and cephaloridine were only 6 and 16 mug/ml, respectively. Here, too, T-tube levels reflected serum concentrations and obstruction to biliary flow impaired excretion of each of the drugs.

Effect of probenecid on the excretion of ampicillin in human bile

1. Ampicillin concentrations were determined in serum and bile after intravenous injection into patients with T-tube bile drainage of 1 gram ampicillin before and during probenecid medication. The concentrations were followed up to fifteen hours after injection.2. Probenecid increased the half-life of ampicillin in serum from 74 minutes to 137 minutes.3. Ampicillin concentrations in bile were higher following probenecid medication and a concentration over 5 mug/ml was obtained for 3 h longer than before probenecid.4. The ampicillin concentrations in bile were approximately the same as those in serum both before and during probenecid medication suggesting passive transport of ampicillin from blood to bile.5. A combined treatment of ampicillin and probenecid might be of clinical value in the therapy of cholangitis and typhoid carriers.

Rifamide in acute cholecystitis and biliary surgery

Determination of the minimum inhibitory concentrations of rifamide necessary to inhibit organisms isolated from the biliary tract showed that the organisms were almost invariably sensitive to concentrations which are readily attainable in the biliary tract. Three cases of severe acute inflammation of the biliary tract were treated and this led to rapid clinical improvement. In 61 patients undergoing biliary surgery a random group was given rifamide 150 mg twice daily, beginning 24 hours before operation and continuing for three days afterwards. In the untreated group eight patients had infected bile at operation and five subsequently developed a wound infection. In the rifamide group three had infected bile at operation and only one developed a wound infection. A similar number of postoperative chest infections occurred in each group of patients. There is some evidence of reduction in length of hospital stay in the treated patients.

Ampicillin levels in human bile in the presence of biliary tract disease

Ampicillin levels were measured in the serum and in the bile from both the gall bladder and the common bile duct in patients undergoing surgery for biliary tract diseases. In patients with radiologically non-functioning gall bladders ampicillin was either not present or its concentration was lower than normal. Therapeutic levels were present in the common bile duct of all patients except those with obstruction of the common bile duct. Hence ampicillin fails appreciably to penetrate the obstructed viscus in obstructive biliary tract disease, and it is unlikely to be effective in treating infection associated with this.