Moxalactam pharmacokinetics during hemodialysis.

To establish dosage recommendations, moxalactam elimination kinetics were studied in six anephric patients during hemodialysis and in four anephric patients during the interdialytic period. After a single 1-g intravenous bolus injection, moxalactam elimination half-life was 18.0 plus or minus 0.6 h with a volume of distribution of 20.2 plus or minus 3.6 liters and a plasma clearance of 12.8 plus or minus 2.0 ml/min in four nondialyzed patients. Moxalactam elimination half-life was decreased to 2.7 plus or minus 0.2 h during hemodialysis in six patients. After 4 h, 48.5% of the dose was recovered in the dialysate. The maintenance dose of moxalactam should be decreased to 15% of a normal dose in patients with creatinine clearances less than 10 ml/min, and 50% of a loading dose should be given after hemodialysis.     

Nizatidine disposition in subjects with normal and impaired renal function

To test the hypothesis that renal insufficiency alters nizatidine disposition, we determined the pharmacokinetics of nizatidine and its major metabolite after a single oral dose in normal volunteers and patients with various degrees of renal dysfunction, after a single intravenous dose in normal volunteers and patients with severe renal failure and during hemodialysis. After intravenous administration the elimination half-life increased from 1.5 +/- 0.2 hours in normal volunteers to 6.9 +/- 3.3 hours in patients with renal failure. The plasma clearance decreased from 0.59 +/- 0.07 L/kg/hr in normal volunteers to 0.14 +/- 0.02 L/kg/hr in patients with renal failure. Nizatidine bioavailability was nearly 100% in normal volunteers but decreased to 75% in patients with renal failure. The volume of distribution was 1.3 +/- 0.1 L/kg in normal volunteers and was not different in patients with renal failure. Nizatidine protein binding was about 30% in normal and uremic plasma. The drug was not substantially removed by hemodialysis. Patients with creatinine clearances less than 50 ml/min/1.73 m2 should receive 150 mg nizatidine once each evening. Patients with creatinine clearances less than 20 ml/min/1.73 m2 should receive 150 mg nizatidine every other night.     

Pharmacokinetics of enoxacin and its oxometabolite following intravenous administration to patients with different degrees of renal impairment.

Enoxacin is a fluorinated quinolone with potential clinical use in the treatment of serious infections. Twenty-three patients (age, 19 to 87 years) with different degrees of renal function, including a group undergoing chronic hemodialysis, received enoxacin (400 mg) by intravenous infusion (1 h). Blood samples were collected before infusion; at the end of infusion; and at 5, 10, 20, 30, 45, 60, 90, and 120 min and 3, 4, 6, 12, 18, 24, 48, and 72 h after infusion. Enoxacin and oxoenoxacin concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic parameters (mean +/- standard deviation) were calculated by using a noncompartmental PK model according to creatinine clearances (in milliliters per minute). Total clearance of enoxacin decreased from 4.95 +/- 1.16 ml/min per kg in the group with normal creatinine clearance to 0.76 +/- 0.21 ml/min per kg in the patients with severe renal failure (creatinine clearance, less than 15 ml/min), whereas the elimination half-life increased from 4.5 +/- 1.0 to 20 +/- 5 h, respectively. The elimination of oxoenoxacin (the main metabolite of enoxacin) in urine was markedly decreased when creatinine clearance was less than 15 ml/min. Hemodialysis removed an insignificant amount of enoxacin and oxoenoxacin. These data indicate that as creatinine clearance falls below 30 ml/min, the daily enoxacin dose should be reduced by half. During prolonged administration of enoxacin to patients with creatinine clearances of less than 30 ml/min, the accumulation of oxoenoxacin might lead to unexpected side effects.     

Ceftriaxone pharmacokinetics in patients with various degrees of renal impairment

The effects of renal impairment on the pharmacokinetics of ceftriaxone in humans were examined after intravenous infusion of a 1-g dose over 15 min to 30 renally impaired patients. The study included 12 dialysis patients and 18 patients with severe, moderate, or mild renal impairment. Plasma and, where appropriate, urine and dialysate samples were collected at predetermined times and analyzed for ceftriaxone by high-pressure liquid chromatography. The elimination half-life (group mean ranged from 11.7 to 17.3 h) and plasma clearance (group mean ranged from 529 to 705 ml/h) did not correlate linearly with creatinine clearance. The renal clearance and fraction of dose excreted unchanged in urine were related linearly, however weakly, with creatinine clearance. Ceftriaxone was not removed from plasma to a significant extent during hemodialysis. The half-life was prolonged twofold, the plasma clearance was lowered less than 50%, and the volume of distribution was relatively unchanged in renally impaired patients compared with young or elderly healthy subjects with normal renal function at an equivalent dose. Since these changes are moderate, adjustment in the dosage regimen of ceftriaxone for patients with impaired renal function should not be necessary when ceftriaxone dosage is 2 g or less per day (2 g every 24 h or 1 g every 12 h). It was reported that the elimination half-life of ceftriaxone is substantially prolonged in a small percentage of patients with end-stage renal disease maintained on hemodialysis. Therefore, plasma concentrations of ceftriaxone should be monitored in dialysis patients to determine whether dosage adjustments are necessary.     

Pharmacokinetics of intravenous piperacillin in patients undergoing chronic hemodialysis.

The pharmacokinetic properties of piperacillin, a piperazine derivative of ampicillin, were determined in seven patients with creatinine clearances less than 7 ml/min who were undergoing chronic, intermittent hemodialysis. A two-compartment linear model was used to analyze the data. Mean elimination half-life was 1.26 +/- 0.1 h; the mean elimination constant was 0.95 +/- 0.08 h-1; the mean volume of distribution was 0.16 +/- 0.02 liters/kg of body weight; the mean volume of the central compartment was 0.10 +/- 0.01 liters/kg of body weight; and the mean clearance was 0.09 +/- 0.01 liters/h per kg of body weight. Mean elimination half-life while off dialysis of 2.1 h.     

Multiple-dose pharmacokinetics of amdinocillin in healthy volunteers.

The pharmacokinetics of amdinocillin (mecillinam) after multiple intravenous doses to healthy subjects are described. Assay of plasma and urine samples was carried out with a sensitive and specific high-pressure liquid chromatographic technique. A dose of 10 mg/kg of body weight was administered every 4 h for six doses. No accumulation was noted. Mean peak plasma concentrations were approximately 50 micrograms/ml, and the plasma half-life was approximately 53 min. Total plasma clearance was 4.6 ml/min per kg after the first dose, which declined slightly to 4.1 ml/min per kg after the last dose. Renal clearance remained fairly constant at approximately 2.9 ml/min per kg, or twice the creatinine clearance. The fraction excreted unchanged totaled 63% during the 4-h interval after the first dose and was nearly 70% overall. The steady-state volume of distribution was calculated to be 0.26 liter/kg. Urinary concentrations of amdinocillin were far in excess of the usual inhibitory concentrations for susceptible pathogens and were as high as 3,000 micrograms/ml. Dose of amdinocillin every 4 h provide plasma and urine concentrations which should be effective for the treatment of infections.     

Pharmacokinetics of ceftizoxime in subjects with various degrees of renal function.

The pharmacokinetics of ceftizoxime (FK-749) were studied in 20 volunteers with various degrees of renal function. Creatinine clearances ranged from zero to 157 ml/min per 1.73 m2. One gram of ceftizoxime was administered by a 30-min drip infusion, and blood and urine samples were collected for up to 48 h after drug administration. For volunteers with a creatinine clearance of greater than or equal to 80 ml/min per 1.73 m2 (group I), the mean half-life was 1.65 h, whereas for volunteers with a creatinine clearance of less than 10 ml/min per 1.73 m2 (group IV), the half-life was 34.7 h. The volume of distribution at steady state (Vdss) and the volume of distribution area (Vdarea) were calculated for each group and ranged from 0.377 to 0.263 and 0.421 to 0.264 liters/kg for groups I and IV, respectively. Total body clearance of ceftizoxime correlated with creatinine clearance (r = 0.953), and the mean urinary recovery of unchanged drug in normal volunteers was 72.4%. A 4-h hemodialysis procedure reduced serum ceftizoxime concentrations by approximately 52%; however, serum concentrations at 48 h after drug administration were still greater than 10 micrograms/ml in dialysis subjects. By using the relationship between total body clearance of ceftizoxime and creatinine clearance, a nomogram was developed to assist in the administration of ceftizoxime to patients with renal dysfunction.     

Pharmacokinetics of Cefamandole in Patients with Renal Impairment

Cefamandole pharmacokinetics were investigated in 24 adult males with stable renal function and creatinine clearances of 0 to 139 ml/min. After intramuscular injection of 1.0 g of cefamandole, peak plasma concentrations were achieved between 1 and 2 h. Maximum plasma concentration and drug half-life increased as creatinine clearance decreased; i.e., with normal renal function the half-life was 1.49 +/- 0.10 h, and in anephrics the half-life was 11.48 +/- 1.91 h. The greatest increase in half-life occurred when the creatinine clearance was less than 20 ml/min. At these levels of renal impairment, there was significant variance in calculated half-life among patients. The maximum urine concentration and rate of cefamandole urinary excretion decreased as renal function declined. Evidence suggesting renal and nonrenal methods of drug elimination is presented. Hemodialysis resulted in increased cefamandole elimination.     

Pharmacokinetics and dosage adjustment of cefotiam in renal impaired patients

The pharmacokinetics of cefotiam were investigated after intravenous administration of 1 g to 2 healthy volunteers with normal renal function and to 16 patients whose creatinine clearance ranged from 4.7 to 0.1 l/h (78 to 1.66 ml/min). The elimination half-life varied from 1.1 h in normal subjects to 13 h in patients and the total plasma clearance from 21 to 0.6 l/h (350 to 10 ml/min). The urinary recovery decreased from 62% of the dose in normal subjects to 1.1% in patients, and the renal clearance from 15 to 0.01 l/h (250 to 0.5 ml/min). Plasma and renal clearances of cefotiam correlated well with the creatinine clearance. The dosage schedule for cefotiam in patients with normal renal function can be used in the presence of renal failure when the creatinine clearance is equal to or greater than 1 l/h (16.6 ml/min). For patients whose creatinine clearance is less than 1 l/h, the dose must be decreased to 75% of that for a patient with normal renal function only when it is given every 6 or 8 h.     

Cefoxitin pharmacokinetics: relation to three different renal clearance studies in patients with various degrees of renal insufficiency.

The pharmacokinetics of cefoxitin were examined in 4 healthy volunteers, 6 patients with normal renal function (inulin clearance, greater than 80 ml/min per 1.73 m2), and 35 patients with various degrees of renal insufficiency (inulin clearance, 80 to less than 5 ml/min per 1.73 m2). A single dose of 30 mg of cefoxitin per kg of body weight was injected intravenously over 3 min. Antibiotic concentrations in plasma were determined by the agar diffusion technique. The cefoxitin half-life increased progressively from 39 min in subjects with normal renal function to 23.5 h in oligoanuric patients. Correspondingly, total body clearance decreased from 340 to 13 ml/min per 1.73 m2. In addition to the study of cefoxitin kinetics, in 29 of the 41 patients, three different renal clearance tests were performed (inulin, p-aminohippurate, and creatinine clearances). Of these, p-aminohippurate clearance showed the best correlation with the elimination rate constant beta as well as total body clearance of cefoxitin; but with respect to beta, the differences between the p-aminohippurate and creatinine clearances were quantitatively negligible. Therefore, even in substances which are eliminated predominantly by active tubular secretion, creatinine clearance could be recommended for dosage adjustments.     

Pharmacokinetics of ceftazidime in normal and uremic subjects.

The pharmacokinetics of ceftazidime, administered as a single intravenous dose of 15 mg/kg given in a bolus injection over 3 min, were investigated in 5 normal subjects and in 19 uremic patients. The subjects studied were divided into five groups according to values for endogenous creatinine clearance (CLCR): group I, five subjects with CLCR greater than 80 ml/min; group II, five patients with CLCR = 30 to 80 ml/min; group III, six patients with CLCR = 10 to 30 ml/min; group IV, four patients with CLCR = 2 to 10 ml/min; and group V, four anuric patients on hemodialysis. A two-compartment open model was used to calculate the pharmacokinetic parameters. In normal subjects, the mean apparent elimination half-life was 1.57 +/- 0.13 h. The central distribution volume and the apparent volume of distribution were 0.127 +/- 0.023 and 0.230 +/- 0.015 liter/kg, respectively. Of the injected dose, 83.6 +/- 3.6% was eliminated in the urine as parent drug within 24 h. The terminal half-life increased with impairment of renal function to about 25 h in severely uremic patients. Impairment of function did not significantly modify the half-life at alpha phase, central distribution volume, or apparent distribution volume. A 6- to 8-h hemodialysis procedure reduced concentrations of ceftazidime in plasma by approximately 88%, and the elimination half-life was 2.8 +/- 0.2 h. There was no evidence of accumulation of ceftazidime in four patients with severe and chronic impairment of function who received doses of 0.5 to 1.0 g every 24 h for 10 days.     

Pharmacokinetics of Amoxicillin: Dosage Nomogram for Patients with Impaired Renal Function

Amoxicillin pharmacokinetics after intravenous administration were studied in patients with normal renal function, with impaired renal function, and during hemodialysis. The average urinary recovery was 68% in patients with normal renal function. Serum half-life was highly correlated (r = 0.967) with creatinine clearance corrected for body weight. Expected half-life was 71 min for a corrected creatinine clearance of 100 ml/min per 70 kg and 16 h in the anephric patient. Average amoxicillin half-life on hemodialysis was 3.6 h. We present a dosage nomogram for making appropriate adjustments to loading dose based on patient weight and maintenance dose based on corrected creatinine clearance.     

Effects of impaired renal function, hemodialysis, and peritoneal dialysis on the pharmacokinetics of mezlocillin

The pharmacokinetics of mezlocillin were examined in 8 patients with normal renal function (inulin clearance, > 80 ml/min per 1.73 m2), 32 patients with moderately reduced renal function (inulin clearances, 80 to 5 ml/min per 1.73 m2), and 12 patients maintained by hemodialysis or peritoneal dialysis because of severely impaired renal function. A single dose of 60 mg of mezlocillin per kg of body weight was infused intravenously over 30 min. Antibiotic concentrations in plasma, urine, and dialysate were determined by the agar diffusion technique. The half-life of mezlocillin increased with decreasing renal function from an average of 53 min in subjects with normal function to 165 min in oligoanuric patients. The urinary recovery of this drug in 24 h decreased from 65% at a glomerular filtration rate of 92 ml/min to 7.6% at a glomerular filtration rate of 6.7 ml/min. Volume of distribution was not changed by the renal insufficiency, amounting on the average to 22.5% of body weight. Intermittent hemodialysis or peritoneal dialysis contributed to only a minor degree to the 24-h mezlocillin kinetics. The pharmacokinetic properties of mezlocillin permit a normal dosage over wide ranges of renal insufficiency; however, when the glomerular filtration rate is below 10 ml/min, the dosage interval should be increased from 8 to 12 h.     

Pharmacokinetics of piperacillin in patients with moderate renal failure and in patients undergoing hemodialysis.

The pharmacokinetics of piperacillin administered intravenously were studied in five patients with stable mild to moderate renal impairment and in five patients undergoing hemodialysis. Patients with stable renal failure given 1 g of piperacillin intravenously had peak serum concentrations within 30 min ranging from 78 to 280 micrograms/ml. The mean serum half-life was 3.57 +/- 1.36 h; the mean apparent volume of distribution was 28.6 +/- 13.5 liters/100 kg; and the plasma clearance was 4.10 +/- 1.46 liters/h per 1.73 m2. Neither serum half-life nor clearance correlated with serum creatinine, implying significant nonrenal elimination. Patients undergoing hemodialysis had peak serum concentrations within 30 min of 66 to 138 micrograms/ml after 1 g of piperacillin infused intravenously. During hemodialysis, the serum half-life was 3.6 +/- 2.5 h; the mean apparent volume of distribution was 26.7 +/- 16.7 liters/100 kg; and the plasma clearance was 3.28 +/- 0.76 layers/h per 1.73 m2. Mean hemodialysis clearance was 0.484 +/- 0.282 liters/h per 1.73 m2, and only 10.0 +/- 5.3% of the total dose could be recovered in the dialysate.     

Pharmacokinetics of tobramycin and gentamicin in abusers of intravenous drugs.

The kinetics of aminoglycoside elimination were determined in 18 hospitalized narcotics abusers receiving gentamicin or tobramycin for treatment of severe infection. Rapid aminoglycoside elimination (requiring doses of greater than 5 mg/kg per day to maintain adequate drug levels) was noted in 12 of the 18 patients (18 of 27 clearance studies). Patients found to have rapid elimination were younger (P less than 0.01) and had larger drug distribution volumes (P less than 0.005), greater measured creatinine clearances (P less than 0.05), and lower creatinine levels in serum (P less than 0.001) than those with normal elimination. Nevertheless, by regression analysis, age, creatinine levels in serum, creatinine clearances, and drug distribution volumes proved to be unreliable predictors of individual aminoglycoside clearance. Measured drug half-life in serum appeared to be the only reliable predictor of drug clearance (r = 0.93). Patients with rapid drug elimination had aminoglycoside clearances 16 to 43% greater than measured creatinine clearances, suggesting an extraglomerular route of drug elimination. We conclude that in drug abuse patients a significant and clinically unpredictable interpatient variation occurs in aminoglycoside elimination and that accurate serum kinetics are needed to determine therapeutic dosing. In addicts younger than 35 years, with a creatinine level of less than 1.0 mg/100 ml in serum, the risk of inadequate therapy is high if standard dosing guidelines are followed. For this group, initial dosing of 8 mg/kg per day, with a drug half-life determination on the first dose, is recommended. Pharmacokinetic analysis is critical for all drug abusers treated with aminoglycosides for serious infection.     

Disposition kinetics of cefamandole during continuous ambulatory peritoneal dialysis.

Cefamandole disposition kinetics were examined in six male subjects with renal impairment who were undergoing continuous ambulatory peritoneal dialysis. Creatinine clearance values ranged from less than 1 to 11 ml/min. Cefamandole was given as a 1-g intravenous dose infused over 30 min. Cefamandole concentrations were determined in serum, urine, and dialysis fluid by a high-performance liquid chromatographic method. The following average parameter values were obtained (range): half-life, 6.1 h (4.6 to 9.7); systemic clearance, 21.9 ml/min (8.4 to 35.5); renal clearance, 11.5 ml/min (0.03 to 22.3); dialysis clearance, 0.92 ml/min (0.7 to 1.3); nonrenal clearance, 12.2 ml/min (2.9 to 27.0); volume of distribution, 0.18 liter/kg (0.09 to 0.25); steady-state volume of distribution, 0.17 liter/kg (0.09 to 0.24). Approximately 5% of the dose was dialyzed (range, 2.8 to 8.3), indicating that there is no need to supplement a dosing regimen of cefamandole due to loss by dialysis. There was a positive correlation between creatinine clearance and the terminal elimination rate constant of cefamandole (r2 = 0.41) and cefamandole renal clearance (r2 = 0.83).     

Pharmacokinetics of moxalactam in patients with renal insufficiency.

Moxalactam pharmacokinetics were determined in 18 patients with renal insufficiency (creatinine clearance, 0 to 99 ml/min). Each patient was given 0.5 g of moxalactam intramuscularly. Drug half-life ranged from 4.1 to 49.1 h and correlated inversely with creatinine clearance (r = -0.97). Total body drug clearance ranged from 0 to 88 ml/min, and renal clearance ranged from 0 to 57 ml/min. In four patients studied during hemodialysis, drug half-life was 21.7 +/- 7.5 h (mean +/- standard error) between dialyses and 4.4 +/- 0.5 h during dialysis. Moxalactam dialysance averaged 44 +/- 2 ml/min per m2 of dialyzer surface area, and approximately 50% of the drug was removed during a single hemodialysis. We confirmed that moxalactam is eliminated from the body primarily by renal excretion. Recommendations are given for dosage adjustment in patients with renal insufficiency.     

Pharmacokinetics of Azlocillin in Subjects with Normal and Impaired Renal Function

The pharmacokinetics of azlocillin were investigated in five healthy subjects and in 16 subjects with chronic renal failure. After intravenous bolus injection of a single dose of 30 mg/kg in normal subjects, pharmacokinetic data were calculated, using a two-compartment open body model. The mean distribution serum half-life (T_1/2α) was 0.11 h, and the mean elimination serum half-life (T_1/2β) was 0.89 h. The volume of the central compartment (V_C) was 7.36 liters/1.73 m², and the apparent volume of distribution (V_dss) was 14.15 liters/1.73 m², i.e., 21.9% of body weight. The T_1/2β after a 30-min intravenous infusion of 80 mg/kg to the same healthy subjects was 1.11 h. Serum clearances (C_S) for the 30- and 80-mg/kg doses were 215.0 and 152.9 ml/min per 1.73 m². The mean renal clearances (C_R) were 145.2 and 94.1 ml/min per 1.73 m² for the respective doses. Between 61.8 and 69.6% of the injected dose was recovered in urine during the first 24 h. The elimination half-life in subjects with chronic renal impairment increased with the degree of renal insufficiency. After a 30-min intravenous infusion of 80 mg/kg the T_1/2β values were 2.03, 4.01, and 5.66 h with creatinine clearances (C_cr) within 30 to 50, 10 to 30, and <10 ml/min per 1.73 m², respectively. Urinary elimination was inversely related to the degree of renal impairment. In four patients out of and on a 6-h hemodialysis session mean elimination half-life values were 6.53 and 2.81 h, respectively. The fraction of drug removed by dialysis was 45.8%. The linear relationships between the elimination of half-life (T_1/2β) and serum creatinine and the elimination rate constant (β) and creatinine clearance (C_cr) provided a basis for adjustment of dosage in renal failure.     

Pharmacokinetics of tobramycin in patients with stable renal impairment, patients undergoing peritoneal dialysis, and patients on chronic hemodialysis

The pharmacokinetics of tobramycin were studied in five patients with stable renal impairment, four patients requiring peritoneal dialysis, and four patients on chronic hemodialysis. The half-life of the drug varied with the level of the serum creatinine in the first group of patients, and the average volume of distribution was 15 liters. Only 49% of the administered dose of tobramycin was recovered during 36 h of peritoneal dialysis. The average clearance of tobramycin during hemodialysis was 49.1 ml/min, and 51.5% of the administered dose was recovered during a 6-h dialysis.     

Pharmacokinetics of cefixime (CL 284,635; FK 027) in healthy subjects and patients with renal insufficiency.

The pharmacokinetics of the extended-half-life, broad-spectrum oral cephalosporin cefixime (CL 284,635; FK 027) were studied in 7 healthy volunteers and 35 patients with various degrees of renal insufficiency, including patients undergoing continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis. Apparent total body, renal, and apparent nondialysis-nonrenal clearances and protein binding declined and elimination half-life increased with decreasing creatinine clearance. All of these alterations became statistically significant as the creatinine clearance fell below 20 ml/min per 1.73 m2. Cefixime concentrations in urine exceeded the MICs for most urinary tract pathogens for up to 24 h postdose, even in patients with severe renal insufficiency. CAPD removed an insignificant fraction of cefixime body burden over the 72-h study period (1.57 +/- 0.60% [mean +/- the standard error of the mean]). Area under the curve data suggested that hemodialysis similarly removed an insignificant fraction of the cefixime body burden. Volume of distribution at steady state was not altered significantly by renal insufficiency. It is recommended that standard doses of cefixime be administered at extended intervals, especially in patients with creatinine clearances less than 20 ml/min per 1.73 m2. In addition, supplemental doses are not necessary during CAPD and at the end of hemodialysis.