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G R Matzke

Publications and source records attributed to G R Matzke.

At least 109 records · Page 6Linked to original sources
PubMed1984

Pharmacokinetics of vancomycin in patients with various degrees of renal function.

The pharmacokinetics of vancomycin were characterized in 56 patients with different degrees of renal function after an intravenous dose of 18.4 +/- 4.7 mg kg-1 (mean +/- standard deviation). Seven subjects had a creatinine clearance (CLCR) of greater than 60 ml min-1 (group I), 13 had a CLCR of 10 to 60 ml min-1 (group II), and 36 had a CLCR of less than 10 ml min-1 (group III). Serial serum samples (range, 3 to 8) were collected during the 168 h after drug administration. The serum concentration-time profile in all patients demonstrated monoexponential decay. The mean half-lives were 9.1, 32.3, and 146.7 h in groups I, II, and III, respectively. A significant decline in serum clearance (CLS) was also noted (62.7 to 28.3 to 4.87 ml min-1 in groups I, II, and III, respectively). The steady-state volume of distribution varied from 0.72 to 0.90 liter kg-1. There was no significant relationship between the steady-state volume of distribution and CLCR. The observed relationship between CLS and CLCR (CLS = 3.66 + 0.689 CLCR; r = 0.8807) can be utilized to devise dosage schedules for patients with any degree of renal impairment. This relationship was utilized to develop a nomogram for initial and maintenance dosing of vancomycin.

Adolescent↗
PubMed1984

Pharmacokinetics of vancomycin in patients undergoing continuous ambulatory peritoneal dialysis.

The pharmacokinetics of vancomycin were studied in four patients on continuous ambulatory peritoneal dialysis. After a single intravenous infusion of 10 mg/kg of total body weight, multiple blood, urine, and dialysate samples were collected during a 72-h evaluation period. The steady-state volume of distribution was 0.73 +/- 0.07 (mean +/- standard deviation) liters/kg with a beta half-life of 90.2 +/- 24.2 h. The continuous ambulatory peritoneal dialysis clearance of vancomycin was 1.35 +/- 0.35 ml/min, and the serum clearance was 6.4 +/- 1.1 ml/min. Peritoneal dialysate concentrations of vancomycin were rapidly attained after the intravenous infusion and averaged 2.2 +/- 0.7 mg/liter throughout the 72-h observation period. A loading dose of 23 mg/kg followed by a maintenance dose of 17 mg/kg every 7 days should attain and maintain therapeutic serum and dialysate concentrations. More frequent dosing may be necessary for less susceptible organisms.

Adult↗
PubMed1984

Analytical accuracy of determinations of aminoglycoside concentrations by enzyme multiplied immunoassay, fluorescence polarization immunoassay, and radioimmunoassay in the presence of heparin.

The accuracy of gentamicin, netilmicin, and tobramycin concentration determinations by enzyme multiplied immunoassay technique (EMIT; Syva Corp., Palo Alto, Calif.), fluorescence polarization immunoassay (TDx; Abbott Diagnostics, Irving, Tex.), and radioimmunoassay were compared in the presence of 0 to 3,000 USP units of porcine heparin per ml. Gentamicin, netilmicin, and tobramycin concentrations determined by EMIT decreased by 10 and 50% in the presence of 75 and 1,000 USP units/ml, 2 and 5 USP units/ml, and 2 and 7.5 USP units/ml, respectively. Accuracy of the TDx and radioimmunoassay determinations, however, were not affected by the presence of heparin. Blood samples for the determination of gentamicin, netilmicin, and tobramycin by EMIT should not be collected in evacuated heparinized tubes.

Aminoglycosides↗
PubMed1984

Stability of gentamicin and tobramycin in concentrate solutions for automated peritoneal dialysis.

Stability of gentamicin and tobramycin in 30 and 50% dextrose peritoneal dialysate concentrate (PDC) fluids was determined at room temperature. All solutions were prepared and stored at 23 degrees C and aliquots were obtained at 0, 1, 2, 4, 8, 12, 24, and 48 h. A degradation rate constant Kdeg was calculated from the concentration time curve of each solution. The length of time required for the gentamicin and tobramycin concentrations to decline to 90% of the initial concentration (t90) was also calculated. The Kdeg of gentamicin in all solutions was less than the Kdeg of tobramycin. The Kdeg increased markedly for gentamicin and tobramycin as the dextrose concentration increased in the PDC. Gentamicin is stable in the 30 and 50% PDC for at least 24 h at 23 degrees C. Tobramycin, however, demonstrated more than a 10% loss of activity in some PDC solutions. If tobramycin is to be added to PDC, especially the 50% dextrose solution, it should be used within 12 h after admixture.

Drug Stability↗
PubMed1984

Heparin interferes with tobramycin serum concentration determinations by Emit.

Enzyme multiplied immunoassay (Emit) commonly is used to determine aminoglycoside concentrations. Its accuracy generally is comparable to that of radioimmunoassay (RIA). Poor reproducibility and questionable quantitation by the Emit assay have been reported when heparinized, severely lipemic, or icteric samples have been used. However, the significance of these interferences is documented poorly. We observed a ESRD patient in whom the underestimation by Emit of the tobramycin concentration in a plasma sample (heparin concentration of 41 U/ml) could have resulted in excessive drug administration and potential toxicity. Tobramycin therapy was initiated with a loading dose of 1.6 mg/kg and three tobramycin concentrations were obtained (2, 12, and 36 hours post-infusion) to define the patient's pharmacokinetic parameters. The first and third samples were collected in serum specimen tubes while the second sample was collected in a plasma tube. The tobramycin concentration in the plasma sample measured by Emit was 82 percent lower than the RIA value. Analyses of other samples by both procedures revealed no clinically significant differences. This case demonstrates that the presence of heparin may interfere with the Emit tobramycin assay in the clinical setting. The degree of reduction in tobramycin concentrations may be dramatic and potentially can alter a patients apparent tobramycin dosing requirements. Further investigation is warranted.

Adult↗
PubMed1984

Trimethoprim-sulfamethoxazole pharmacokinetics during continuous ambulatory peritoneal dialysis.

Eight adult patients without peritonitis maintained on chronic ambulatory peritoneal dialysis (CAPD) were administered a single oral dose of 320 mg trimethoprim (TMP) and 1600 mg sulfamethoxazole (SMX) to characterize the pharmacokinetics of TMP and SMX. Ten blood samples were drawn following the dose. TMP and SMX-active (SMXA) concentrations were quantified in serum and dialysate. The half-life of TMP and SMXA determined by model independent methods were 33.7 +/- 10.5 h (mean +/- SD) and 13.8 +/- 2.2 h respectively. Total body clearance of TMP was 32.8 +/- 10.1 ml/min and SMXA was 21.9 +/- 6.4 ml/min. CAPD clearance of TMP was 2.27 +/- 0.81 ml/min and SMXA was 1.72 +/- 0.93 ml/min. The average peritoneal dialysate concentrations over the 72-hour collection period of TMP and SMXA were 0.9 +/- 0.1 mg/l and 5.3 +/- 0.8 mg/l respectively. A dose of 320 mg TMP and 1600 mg SMX every 48 hours is recommended for CAPD patients with mild to moderate systemic infections.

Administration, Oral↗
PubMed1983

Cefsulodin pharmacokinetics in patients with various degrees of renal function.

The pharmacokinetics of cefsulodin were characterized in 19 patients with different degrees of renal function after a single 500-mg, 30-min intravenous infusion. Six subjects had a creatinine clearance (Clcr) of greater than 100 ml min-1 (group I), eight had a Clcr of between 12 and 42 ml min-1 (group II), and five had a Clcr of less than 10 ml min-1 (group III). Nine plasma and four urine samples were collected in the first 36 h. The plasma concentration-time data were fitted to a two-compartment open model. The mean beta-phase half-life was 1.77, 6.37, and 10.12 h in groups I, II, and III, respectively. A significant decline in plasma clearance (Clp) was also noted between the three groups: 136 to 49.6 to 27.2 ml min-1 in groups I, II, and III, respectively. Steady-state volume of distribution was 0.26 liter kg-1, regardless of renal function. The observed linear relationship between Clp and Clcr (Clp = 24.09 + 0.765 Clcr; r = 0.9566) can be utilized to revise dosage schedules for patients with any degree of renal impairment. The nonrenal clearance of cefsulodin was also noted to be significantly lower in groups II and III than in group I. Further investigations will be necessary to elucidate the mechanism(s) responsible for the decrease in the nonrenal clearance of cefsulodin.

Adult↗
PubMed1983

Gentamicin and tobramycin dosing guidelines: an evaluation.

The provision of pharmacokinetic dosing services has become a cornerstone of clinical pharmacy practice in many institutions. As these services expand, more pharmacists will become involved, and the need for a structured, uniform approach to the provision of these services may be necessary. Therefore, this article discusses specific approaches (i.e., guidelines) to the most common clinical conditions that the pharmacist may encounter. The goal is to promote consistent interpretation and application of clinical and kinetic data by the members of our aminoglycoside dosing service. The guidelines provide a structured yet adaptive approach to the clinical use of gentamicin and tobramycin. The major areas of controversy that were encountered in developing these guidelines are discussed, and the guidelines are presented. These guidelines currently are used to standardize our pharmacokinetic dosing service and as a tool for educating new pharmacists to their role and responsibilities as members of the pharmacokinetic consultation team. Additionally, these guidelines are being used as criteria for the assessment of quality assurance in the area of clinical pharmacokinetics.

Adult↗
PubMed1983

Bumetanide: a new loop diuretic (Bumex, Roche Laboratories).

Bumetanide is a recently introduced diuretic that inhibits sodium transport in the thick ascending limb of the loop of Henle. It is structurally and pharmacologically similar to furosemide, but is approximately 40 times as potent on a milligram-for-milligram basis. After oral administration, it is rapidly absorbed, with peak serum concentrations attained at approximately 30 minutes. Its pharmacokinetic parameters are similar to those of furosemide. Bumetanide has demonstrated efficacy in the management of edema associated with congestive heart failure, hepatic cirrhosis, and renal insufficiency. Bumetanide has demonstrated an adverse-reaction profile similar to that of furosemide, although the incidence of hypochloremia and hypokalemia is greater with bumetanide. The incidence of hyperglycemia and ototoxicity is greater with furosemide. The principal indication for bumetanide may be in patients with increased risk of ototoxicity. Cost considerations should relegate bumetanide to a secondary role for the treatment of sodium and fluid retention in most clinical settings.

Animals↗
PubMed1982

Evaluation of three gentamicin serum assay techniques.

This investigation was designed to compare the enzyme-modified immunoassay (Syva--EMIT) with a radioimmunoassay (New England Nuclear--RIA) and the radiometric assay (Johnston--BACTEC) to determine the optimal assay for use in our aminoglycoside dosing service. The serum concentration determinations obtained via the three assay methods were analyzed by linear regression analysis. Significant positive correlations were noted between the three assay techniques (p less than 0.005) during both sample collection phases. The coefficients of determination for EMIT vs BACTEC and RIA vs BACTEC were 0.73 and 0.83 during phase 1, respectively, and 0.65 and 0.68 during phase 2, respectively. The slope of the regression lines also varied markedly during the two phases; 0.49 and 0.42 for EMIT and for RIA vs BACTEC, respectively, during phase 1 compound with 1.12 and 0.77, respectively, during phase 2. The differences noted in these relationships during phase 1 and 2 may be related to the alteration of the pH of the control sera utilized in the BACTEC assay. In contrast, RIA vs EMIT regression analysis indicated that existence of a highly significant relationship (p less than 0.0005 and r2 = 0.90). The EMIT technique was the easiest and most accurate for determination of serum gentamicin concentrations, whereas the BACTEC method was judged unacceptable for clinical use.

Carbon Radioisotopes↗
PubMed1981

The treatment of hypertension in pregnancy.

The drug treatment of hypertension occurring during pregnancy is described. Diagnostic problems and management are outlined, and the available literature regarding the use of standard hypotensive agents in pregnancy is reviewed by drug class. Based on currently published literature and opinion, the following drugs are recommended when needed during pregnancy (with proper monitoring) : methyldopa, hydralazine, and furosemide. Caution is recommended when the following drugs are used during pregnancy: propranolol, and thiazide diuretics. The following drugs are not recommended for use during pregnancy based on currently available information: reserpine, clonidine, chlorthalidone, prazosin, minoxidil, spironolactone, ethacrynic acid, metoprolol, nadolol, and guanethidine.

Adrenergic beta-Antagonists↗
PubMed1981

Elevated serum phenytoin concentrations in a uremic patient when measured by enzyme-multiplied immunoassay.

A patient with chronic renal failure did not respond to "therapeutic" serum phenytoin concentrations as measured by enzyme-multiplied immunoassay (EMIT). Her seizure disorder was not controlled despite phenytoin concentrations of 25-35 micrograms/ml. When her serum samples were reassayed by high pressure liquid chromatography and gas-liquid chromatography, the phenytoin serum concentrations were found to be approximately 1/2 of the previously reported values, that is, 16.0 micrograms/ml vs. 33 micrograms/ml. The precise reason for this discrepancy is currently unknown. Our findings suggest that the EMIT assay may yield falsely elevated serum phenytoin concentrations in uremic subjects.

Female↗
PubMed1981

Nephropathy as a hazard of analgesic abuse.

Analgesic nephropathy is discussed. It has been estimated that 5-7% of all patients with chronic renal failure have a history of excessive analgesic use. Chronic analgesic abusers are predominantly women (3:1), and the peak incidence is between the ages of 40-60. Most analgesic abusers have some psychoneurosis with a history of headaches, backaches, arthritis, or ulcers. Several mechanisms for this nephrotoxicity have been proposed. It is thought that the ingestion of aspirin with phenacetin modifies the metabolism or alters the renal tissue response to one of these two drugs in such a manner as to increase toxicity. It has been proposed that the oxidative metabolites of phenacetin act in conjunction with aspirin to cause papillary necrosis. Chronic renal failure, a history of excessive analgesic use, radiological evidence of papillary necrosis, and clinical evidence of hematuria and mild proteinuria may confirm the diagnosis of analgesic nephropathy. Pharmacists should be aware of the indicence of analgesic nephropathy, and the general profile of patients who abuse analgesics. Early detection and cessation of analgesic use may avert progressive renal failure. Pharmacists should advise patients on the long-term complications of chronic analgesic use.

Adult↗
PubMed1980

Development of competency standards for quality assurance in clinical pharmacokinetics.

In response to an editorial in Hospital Pharmacy which called for "in-house credentialling" of pharmacists engaged in the application of clinical pharmacokinetics, a method of introducing quality assurance in pharmacokinetics is presented. The evolution of a pharmacokinetic dosing service in which each pharmacist is responsible for the provision of dosage recommendations on his/her patient care area is discussed, along with the difficulties which had to be overcome in order to establish uniform guidelines for our clinical pharmacy staff to follow when providing this service. Finally, the establishment of acceptable levels of competence, means of obtaining those levels, and methods for the determination of competence are presented.

Aminoglycosides↗