Pharmacokinetics of sulfamethoxazole--trimethoprim combination during chronic peritoneal dialysis: effect of peritonitis

A Physiologically-Based Pharmacokinetic Model of Trimethoprim for MATE1, OCT1, OCT2, and CYP2C8 Drug-Drug-Gene Interaction Predictions

Trimethoprim is a frequently-prescribed antibiotic and therefore likely to be co-administered with other medications, but it is also a potent inhibitor of multidrug and toxin extrusion protein (MATE) and a weak inhibitor of cytochrome P450 (CYP) 2C8. The aim of this work was to develop a physiologically-based pharmacokinetic (PBPK) model of trimethoprim to investigate and predict its drug–drug interactions (DDIs). The model was developed in PK-Sim^®, using a large number of clinical studies (66 plasma concentration–time profiles with 36 corresponding fractions excreted in urine) to describe the trimethoprim pharmacokinetics over the entire published dosing range (40 to 960 mg). The key features of the model include intestinal efflux via P-glycoprotein (P-gp), metabolism by CYP3A4, an unspecific hepatic clearance process, and a renal clearance consisting of glomerular filtration and tubular secretion. The DDI performance of this new model was demonstrated by prediction of DDIs and drug–drug–gene interactions (DDGIs) of trimethoprim with metformin, repaglinide, pioglitazone, and rifampicin, with all predicted DDI and DDGI AUC_last and C_max ratios within 1.5-fold of the clinically-observed values. The model will be freely available in the Open Systems Pharmacology model repository, to support DDI studies during drug development.

The Antimicrobial Implications of the Pharmacokinetics of Cotrimoxazole in CAPO Patients

Cotrimoxazole (TMP/SMX) has been used to treat continuous ambulatory peritoneal dialysis (CAPD) associated peritonitis. It is considered bactericidal for some species. The most common single organism responsible for this type of peritonitis is Staph. epidermidis (SE). When the drug is given orally, the typical ratio of TMP to SMX achieved in the peritoneal fluid is 1:5, which is different from the optimal combination for antimicrobial synergy of 1:19. This study investigated the antimicrobial activity of TMP alone and TMP/SMX by agar dilution at ratios of 1:19, 1:10 and 1:5 against 99 strains of Staphylococcus epidermis (SE). The majority of strains were susceptible to TMP and to all ratios of TMP/SMX by the routine agar dilution methods. We studied the bactericidal activity of TMP/SMX against one strain each of SE and of Staph. aureus (SA) in pooled uninfected spent dialysate by killing curve experiments. TMP at concentrations of 0.5 to 2.0 μg/ml was bacteriostatic. TMP/SMX became slowly bactericidal when 5 % lysed horse blood, a source of thymidine phosphorylase, was added to the dialysate.

It is concluded that susceptibility tests of inhibition do not predict bactericidal activity of TMP/SMX in recovered dialysate. Inhibition of TMP/ SMX is most likely due to thymidine present in dialysate. TMP alone was as effective against SE as TMP/ SMX. Until it is shown that bactericidal activity is not required for cure of CAPD-related peritonitis, cotrimoxazole should not be used routinely for its treatment.

Trimethoprim-Sulfamethoxazole Pharmacokinetics during Continuous Ambulatory Peritoneal Dialysis (CAPD)

Ten adult patients on continuous ambulatory peritoneal dialysis (CAPO) received one dose of trimethoprim320 mg (TMP) and sulfamethoxazole 1600 mg (SMX) orally (p.o.), intravenously (i.v.), and intraperitoneally (i.p.) on three separate occasions to characterize the pharmacokinetics of both drugs. Concentrations of both TMP and SMX were measured in serum and dialysate by HPLC to 48 h. Half-life, total body clearance (TBC), and peritoneal clearance (PCI) were determined. The mean half-life of TMP was 28 h, while for SMX it was 12.5 h. Relative to the i.v. dose, the bioavailability following oral administration for TMP was 98% and 87% for SMX. Intraperitoneal bioavailability was 73% for TMP and 65% for SMX after a 4-h dwell.

After 24 h, regardless of the route of administration, less than 3% of TMP and less than 6% of SMX appeared in dialysate.

We conclude that peritoneal losses contribute insignificantly to TMPISMX elimination during CAPO.

Drugs and Peritoneal Dialysis

This paper is a review of the literature describing drug disposition in patients with end-stage renal disease (ESRD) during either intermittent peritoneal dialysis (IPD) or continuous ambulatory peritoneal dialysis (CAPD). The removal of drugs by peritoneal dialysis and drug absorption after intraperitoneal administration are examined. Detailed pharmacokinetic data extracted from the literature are presented in tabular form and are accompanied by specific dosage recommendations for dialyzed patients. Accepted literature values for parameters reflecting the effects of ESRD alone are also included. The construction of a rational dosage regimen with emphasis on the use of the aminoglycosides and the cephalosporins is described.

Bladder catheterization increases susceptibility to infection that can be prevented by prophylactic antibiotic treatment

Catheter-associated urinary tract infections (CAUTI) are the most common hospital-associated infections. Here, we report that bladder catheterization initiated a persistent sterile inflammatory reaction within minutes of catheter implantation. Catheterization resulted in increased expression of genes associated with defense responses and cellular migration, with ensuing rapid and sustained innate immune cell infiltration into the bladder. Catheterization also resulted in hypersensitivity to Enterococcus faecalis and uropathogenic Escherichia coli (UPEC) infection, in which colonization was achieved using an inoculum 100-fold lower than the ID₉₀ for infection of an undamaged urothelium with the same uropathogens. As the time of catheterization increased, however, colonization by the Gram-positive uropathogen E. faecalis was reduced, whereas catheterization created a sustained window of vulnerability to infection for Gram-negative UPEC over time. As CAUTI contributes to poorer patient outcomes and increased health care expenditures, we tested whether a single prophylactic antibiotic treatment, concurrent with catheterization, would prevent infection. We observed that antibiotic treatment protected against UPEC and E. faecalis bladder and catheter colonization as late as 6 hours after implantation. Thus, our study has revealed a simple, safe, and immediately employable intervention, with the potential to decrease one of the most costly hospital-incurred infections, thereby improving patient and health care economic outcome.

Cotrimoxazole - optimal dosing in the critically ill

The optimum dosage regimen for cotrimoxazole in the treatment of life threatening infections due to susceptible organisms encountered in critically ill patients is unclear despite decades of the drug's use. Therapeutic drug monitoring to determine the appropriate dosing for successful infection eradication is not widely available. The clinician must utilize published pharmacokinetic, pharmacodynamic, and effective inhibitory concentration information to determine potential dosing regimens for individual patients when treating specific pathogens. Using minimum inhibitory concentrations known to successfully block growth for target pathogens, the pharmacokinetics of both trimethoprim and sulfamethoxazole can be utilized to establish empiric dosing regimens for critically ill patients while considering organ of clearance impairment. The author's recommendations for appropriate dosing regimens are forwarded based on these parameters.

Semi-automated protein binding methodology using equilibrium dialysis and a novel mixed-matrix cassette approach

A semi-automated protein binding assay using equilibrium dialysis (ED) and a novel mixed-matrix methodology has been developed. This method decreases mass spectrometer run time and reduces the likelihood of experimental artifacts. In this cassette-based approach, a single matrix is prepared following dialysis by mixing dialyzed plasma and buffer containing different test compounds from the same dialysis plate. This approach differs from the traditional mixed-matrix method where fresh plasma and fresh buffer are mixed with opposing dialyzed samples. This new mixed-matrix methodology is compatible with various high-throughput ED and ultrafiltration devices, many liquid handling systems, and can be used for plasma, serum, albumin, alpha-1 acid glycoprotein, microsomal, and fine tissue homogenate binding studies. The utility of the method can be further enhanced by varying the number of replicates, concentrations, and matrices with simple modifications. Using 29 structurally diverse marketed drugs with a wide range of protein binding values reported in the literature, we have shown the new procedure reduces the total number of samples by nearly half compared to traditional methods, eliminates the need for standard curves, and increases the uniformity of the sample matrix for LC/MS/MS analysis.

Novel approach to antibiotic prophylaxis in percutaneous endoscopic gastrostomy (PEG): randomised controlled trial

OBJECTIVE

To evaluate a new and simpler strategy of antibiotic prophylaxis in percutaneous endoscopic gastrostomy (PEG).

DESIGN

Single centre, two arm, randomised, controlled, double blind clinical trial.

SETTING

Endoscopy unit in Karolinska University Hospital, Stockholm, Sweden, between 3 June 2005 and 31 October 2009.

PARTICIPANTS

234 patients with an indication for PEG who gave informed consent to participate.

INTERVENTION

A single 20 ml dose of the oral solution of sulfamethoxazole and trimethoprim (also known as co-trimoxazole or Bactrim; F Hoffmann-La Roche Ltd, Basel, Switzerland) deposited in the PEG catheter immediately after insertion. The control group received standard prophylaxis consisting of a single intravenous dose of 1.5 g cefuroxime (Zinacef; GlaxoSmithKline, London) administered before insertion of the PEG tube.

MAIN OUTCOME MEASURE

Primary outcome was the occurrence of clinically evident wound infection within 14 days after insertion of the PEG catheter. Secondary outcomes were positive bacterial culture and blood tests (highly sensitive C reactive protein and white blood cell count). All randomised patients were included in an intention to treat analysis.

RESULTS

Of the 234 patients included in this study, 116 were randomly assigned to co-trimoxazole and 118 to cefuroxime. At follow-up 7-14 days after insertion of the PEG catheter, wound infection was found in 10 (8.6%) patients in the co-trimoxazole group and 14 (11.9%) in the cefuroxime group, which corresponds to a percentage point difference of -3.3% (95% confidence interval -10.9% to 4.5%). The per protocol analysis, which comprised 100 patients in each group, gave similar results-10% and 13% infection in the co-trimoxazole and cefuroxime groups, respectively (percentage point difference -3.0%, 95% CI -11.8% to 5.8%). Both these analyses indicate non-inferiority of co-trimoxazole compared with cefuroxime because the upper bounds of the confidence intervals are lower than the pre-determined non-inferiority margin of 15%. Analyses of the secondary outcomes supported this finding.

CONCLUSION

20 ml of co-trimoxazole solution deposited in a newly inserted PEG catheter is at least as effective as cefuroxime prophylaxis given intravenously before PEG at preventing wound infections in patients undergoing PEG. Trial registration Current Controlled Trials ISRCTN18677736.

Automated peritoneal dialysis: new implications for pharmacists

OBJECTIVE

To review the new automated peritoneal dialysis (APD) modalities that are available to patients with end-stage renal disease (ESRD), and to examine their potential pharmacokinetic and drug dosing consequences.

DATA SOURCES

A MEDLINE search (from January 1966 to June 1996) of English-language literature pertaining to peritoneal dialysis was performed. Additional references were obtained by reviewing the references of pertinent articles identified through the search. Tertiary sources were also used.

DATA EXTRACTION

Data regarding peritoneal dialysis techniques and pharmacokinetics were extracted from the literature. Data were evaluated according to the study design, population, results, and conclusions.

DATA SYNTHESIS

ESRD is the result of progressive chronic renal insufficiency and requires renal replacement therapy. APD is the fastest growing renal replacement therapy by percentage in the US and provides dialysis exchanges via a machine while the patient sleeps, thereby improving patient convenience, peritoneal dialysis compliance rates, and decreasing peritonitis rates. Well-designed pharmacokinetic studies involving APD have not been conducted. Consequently, no formal drug dosing recommendations are available for APD, and pharmacists must rely on established dosing guidelines for continuous ambulatory peritoneal dialysis (CAPD) when recommending dosing regimens. This article describes the new APD treatment modalities available and the potential pharmacokinetic differences between CAPD and APD.

CONCLUSIONS

Well-designed studies are needed to fully characterize the pharmacokinetic parameters of drugs in APD. Until then, pharmacists should recommend that intraperitoneally administered drugs be given during the longest peritoneal dialysate dwell of the day and that serum concentrations of drugs with narrow therapeutic indices be monitored closely.

Clinical use of trimethoprim/sulfamethoxazole during renal dysfunction

This article reviews the pharmacokinetics, clinical use, and adverse effects of trimethoprim/sulfamethoxazole (TMP/SMX) in renally impaired patients. Renal dysfunction changes the pharmacokinetics of both component drugs. TMP and SMX disposition are not significantly altered until creatinine clearance is less than 30 mL/min, when SMX metabolites and TMP accumulate and may lead to toxicity. Renal dysfunction, however, does not preclude the use of TMP/SMX to treat susceptible infections, even when creatinine clearance is less than 15 mL/min. Adverse effects may occur more frequently in renally impaired patients but are not clearly related to increased serum concentrations of either drug. Guidelines for appropriate dosing and monitoring of TMP/SMX therapy in these patients are presented.

Pharmacokinetics of cefradine, sulfamethoxazole and trimethoprim and their metabolites in a patient with peritonitis undergoing continuous ambulatory peritoneal dialysis

Cefradine and co-trimoxazole pharmacokinetics were studied in a patient with peritonitis that complicated continuous ambulatory peritoneal dialysis (CAPD). Concentrations in the plasma reached after oral administration of 500 mg cefradine four times daily and 400/80 mg co-trimoxazole four times daily were for cefradine 100 micrograms/ml, for trimethoprim 15 micrograms/ml, and for sulfamethoxazole 100 micrograms/ml, respectively. In the dialysate concentrations were reached of 35-70 micrograms/ml cefradine, 2-5 micrograms/ml trimethoprim and 8-17 micrograms/ml sulfamethoxazole. The values for sulfamethoxazole are regarded too low to be clinically effective. Half-lives, protein binding values and CAPD clearances are presented. Low CAPD clearances were obtained during the night and high values during the day. The dosage yielded too high plasma trimethoprim concentrations, while sulfamethoxazole dialysate concentrations were too low. It seems questionable therefore whether co-trimoxazole can be used orally for the treatment of CAPD peritonitis.

Pharmacokinetics of ornidazole in patients with renal insufficiency; influence of haemodialysis and peritoneal dialysis

The pharmacokinetics of ornidazole (Tiberal) was studied after intravenous administration of a single 500 mg dose in eight patients with advanced chronic renal failure (ACRF) (creatinine clearance 2-16 ml/min), in seven patients treated by haemodialysis (residual renal creatinine clearance 0-5 ml/min) and in five patients treated by continuous ambulatory peritoneal dialysis (CAPD) (residual renal creatinine clearance 0-6 ml/min). In ACRF patients, the half-life of ornidazole was 10.8 +/- 1.4 h, the total plasma clearance 46.3 +/- 2.3 ml/min and the volume of distribution 0.73 +/- 0.06 l/kg. During haemodialysis, ornidazole was partly removed: the dialyser extraction ratio was 42 +/- 5% and the dialysis clearance 64 +/- 7 ml/min. During CAPD, peritoneal excretion was low: the dialysis clearance was 3.0 +/- 0.4 ml/min and in 48 h 6.0 +/- 1.1% of the administered dose was found in the peritoneal fluids. In these patients, the half-life of ornidazole was 11.8 +/- 0.8 h and total plasma clearance was 48.3 +/- 5.5 ml/min, values which were close to those determined in non dialysed patients. In patients with end-stage renal disease, the half-life of ornidazole is comparable to that of subjects with normal renal function. This is due to the predominantly extra-renal elimination of the drug. Therefore, there is no need to modify the usual dosage of ornidazole for these patients. Because of the large elimination of the drug during haemodialysis it is necessary to administer the drug after the dialysis session.

Increased peritoneal permeability in patients with peritonitis undergoing continuous ambulatory peritoneal dialysis

The distribution of cefuroxime (250 mg) was studied in patients with renal failure undergoing continuous ambulatory peritoneal dialysis (CAPD). 10 uninfected patients received the drug intravenously and intraperitoneally, while 9 patients with peritonitis were randomly allocated to intravenous or intraperitoneal administration. Samples were taken over the first 6 hour dialysis period. In the infected patients, more drug (p less than 0.01) crossed into the peritoneal cavity following intravenous injection and reached the systemic circulation following intraperitoneal administration than in the uninfected group. This increased permeability of the peritoneal membrane during infection may result in unexpected systemic toxicity in patients treated with intraperitoneal antibiotics.

The pharmacokinetics of antibiotics used to treat peritoneal dialysis-associated peritonitis

Antibiotics continue to be used frequently to treat CAPD-associated peritonitis. Selection of appropriate antibiotic doses and routes of administration has been based largely upon clinical experience. Early pharmacokinetic studies utilized patients being treated with IPD. The relevance of these studies to CAPD remains unknown. Little information exists on the effects of peritonitis on peritoneal drug transport. Until the effects of peritonitis during CAPD are better understood, pharmacokinetic data will be of limited value in designing specific treatment recommendations for this common complication of peritoneal dialysis.

Drug prescribing in renal failure: dosing guidelines for adults

The data base for rational guidelines to safe, efficacious drug prescribing in adults with renal insufficiency are presented in tabular form. Current medical literature was extensively surveyed to provide as much specific information as possible. When information is lacking, however, recommendations are based on pharmacokinetic variables in normal subjects. Nephrotoxicity, important adverse effects, and special considerations in renal patients are noted. Adjustments are suggested for hemodialysis and peritoneal dialysis when appropriate.

Pharmacokinetics of common antibiotics used in continuous ambulatory peritoneal dialysis

To establish therapeutic guidelines for the use of antibiotics in patients receiving continuous ambulatory peritoneal dialysis (CAPD), we studied the single-dose pharmacokinetics of cefazolin, tobramycin, and vancomycin given intravenously (IV) and intraperitoneally (IP) as well as cephalexin given orally. By the IV or oral route, the antibiotics exhibited half-lives similar to those described in nondialysed, functionally anephric patients. CAPD accounted for only a negligible fraction of the total body clearance when the drugs were given by the IV route. However, when given IP, the drugs were promptly absorbed and achieved therapeutic serum concentrations. The kinetic principle of superposition was applied to predict plasma concentrations after repetitive IP dosing. Therapeutic guidelines are provided.