ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:The pharmacokinetics of intravenous theophylline were prospectively studied in 179 premature babies. Interrelated variables were analyzed for their influence on theophylline serum clearance. Gestational age, gender, duration of treatment, body weight, and Apgar scores were not found to correlate significantly with theophylline clearance. Weak but statistically significant correlations were found between serum clearance and postnatal (p < 0.005) and postconceptional age (p < 0.01). No significant difference in mean serum clearance (Cls) values was found between small‐for‐gestational‐age (SGA) patients (Cls= 17.9 ± 5.3 ml/kg/h) and appropriate‐for‐gestational‐age (AGA) patients (Cls= 18.8 ± 5.8 ml/kg/h). Conversely, asphyxiated patients had significantly lower mean clearance values than nonasphyxiated patients (16.4 ± 5.3 ml/kg/h vs. 20.2 ± 5.4 ml/kg/h, respectively, p < 0.001). Volume of distribution for theophylline (n = 147) was 0.77 ± 0.17 L/kg; there was no significant difference in distribution volumes between asphyxiated and nonasphyxiated patients or between SGA and AGA patients. Step‐wise multiple regression analysis revealed postnatal age as the most important determinant of theophylline clearance among the variables analyzed (p < 0.01). Postconceptional age had a statistically significant association with theophylline clearance in the entire group (n = 179, p < 0.05). Duration of treatment had a small and statistically borderline effect (p < 0.10) on theophylline clearance among nonasphyxiated infants when age factors were considered. Analysis of covariance confirmed the statistical effects of both postnatal age and asphyxia on theophylline serum clearance.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:The pharmacokinetics of intravenous rifampin (280 ± 78 mg/m2) were investigated during multiple dose administration in 12 pediatric patients aged 3 months to 12.8 years. Serum rifampin concentration data were fit to a linear one‐compartment model. There was a significant effect of duration of therapy on rifampin clearance (Cl) and half‐life (t1/2) (p = 0.027 and p = 0.048, respectively). A mean increase of 52.0% in Cl (3.10‐4.72 L/h/m2) and a mean decrease of 27.0% in t1/2(2.38‐1.73 h) were observed when data collected during the first 2 days of therapy were compared with data collected following 8 or more days of therapy. Peak concentrations extrapolated to the end of infusion were 27.0 ± 8.2 &mgr;g/ml, and concentrations at 8 h after the dose were only 1.9 ± 1.5 &mgr;g/ml. There was no significant effect of duration of therapy on these concentration values. There was no correlation between Cl and age or administered dose. Intrapatient variation in Cl was great, as evidenced by the lack of correlation of initial Cl values with subsequent values in individual patients (r= 0.259). It would appear that dosage intervals may need to be shortened from 12 to 8 h during continuous therapy, and that periodic measurement of rifampin concentration may be required.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:The absolute bioavailability of oral rifampin was determined in 20 pediatric patients. Intravenous doses of rifampin (mean 287 mg/m2) were compared with p.o. doses (mean 324 mg/m2). Serum concentrations of rifampin, 25‐O‐desacetylrifampicin, and 3‐formylrifamycin SV were determined by high performance liquid chromatography. Following a ½‐h intravenous infusion, serum rifampin concentrations declined in a monoexponential fashion. Pharmacokinetic analysis of the rifampin serum concentration data indicated that only 50 ± 22% of a freshly prepared p.o. suspension was absorbed. The rifampin elimination half‐life following i.v. administration (2.25 ± 0.64 h) was not different from that observed following p.o. dose administration (2.61 ± 1.35 h). Peak rifampin concentrations were significantly higher following i.v. administration when corrected to a 300 mg/m2dose (27.4 vs. 9.1 &mgr;g/ml, respectively, p < 0.0001) than after p.o administration. The peak concentration following a p.o. dose occurred at 2.0 ± 0.9 h. The ratio of desacetylrifampicin to rifampin areas under the curves were similar for i.v. and p.o. routes of administration (0.23 vs. 0.19), suggesting linear metabolism of rifampin to this metabolite. 3‐formylrifamycin SV concentrations were lower than those of desacetylrifampicin and were detectable in less than half of the patients. The results of this study indicate the need for larger p.o. doses when serum concentrations similar to those obtained following intravenous doses are desired.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:Plasma nor1‐chlorpromazine (nor1‐CPZ) and chlorpromazine concentrations were measured by gas chromatography—mass fragmentometry in 15 inpatients receiving stable doses of chlorpromazine. Nor1‐CPZ concentrations averaged 20% of chlorpromazine concentrations and were highly correlated with them. Relative concentrations of nor1‐CPZ increased with age. Nor1‐CPZ concentrations per milligram dose were higher in black than in white patients.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:The effect of total drug concentration on the free fraction was studied in vitro using sera of uremic and nonuremic subjects. Both therapeutic and toxic concentrations of radiolabeled phenytoin, diazepam, and propranolol were used. The free fraction was separated by a pressure ultrafiltration method at 37°C and determined from 200‐&mgr;l aliquots of serum and the ultrafiltrate. Sera from 11 acutely uremic and 10 chronically uremic patients and from 10 healthy control subjects were used. Only slight increases in the free fraction were found over the concentration range studied in both nonuremic and uremic subjects. The concentration‐dependent increases in the unbound fraction of phenytoin and diazepam were quite negligible compared with the two‐ to threefold increases caused by uremia itself. Thus, variation in total concentrations of phenytoin, diazepam, and propranolol does not change the free fractions to a clinically significant degree even in uremic patients with a compromised binding capacity.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:A method to assess heparin kinetics and individualize dosages was examined in 27 patients during chronic hemodialysis. Pretreatment heparin sensitivities were determined to establish the relationship between heparin concentration and activated clotting times (ACTs). Distribution volume was calculated by dividing the heparin loading dose by the 5‐min heparin concentration. Assessments were made during three different dialysis periods. There was a 10‐fold range in pretreatment heparin sensitivities. Intrapatient heparin sensitivity remained relatively consistent between dialysis periods. The degree of heparin sensitivity was significantly correlated to baseline ACT. Patients post‐splenectomy were more sensitive to heparin. Large intra‐ and interpatient variation in distribution volume was also observed. Men, patients <60 years old, and patients post‐splenectomy represented variables that contributed to higher heparin dose requirements.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:Chlorpromazine (CPZ), chlorpromazine sulfoxide (CPZSO), and chlorpromazineN‐oxide (CPZNO) were each incubated (37°C), for various timed intervals up to 60 min, with pooled human whole blood. Plasma and red blood cells were then separated and analyzed by a high performance liquid chromatographic method that avoids the use of alkaline extraction procedures. It was found that CPZ, CPZSO, and CPZNO were remarkably stable in whole blood under physiological conditions. CPZ was converted into CPZSO to a small extent (1%). Reports of 15‐50% conversion of CPZ into CPZSO are largely due to artifacts, which result when red blood cell materials come into contact with alkali. CPZNO was recovered (85%) unchanged from the plasma. A small portion (1%) of the CPZNO was reduced to CPZ in the red blood cells. Thus, on the basis of these in vitro data, blood does not appear to be an important tissue for the metabolism of CPZ, CPZSO, or CPZNO.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Summary:In order to determine the suitability of using tears and saliva to estimate theophylline concentrations, simultaneous plasma, tear, and saliva samples were obtained in 22 adult male patients taking theophylline. Unbound theophylline concentrations were determined by equilibrium dialysis for nine of the subjects and compared with the concentrations determined in saliva and tears. The mean tear/unbound and saliva/unbound ratios were 0.94 ± 0.12,r= 0.88, and 1.25 ± 0.14,r= 0.91, respectively. Tear/plasma ratios ranged from 0.36 to 0.76 (mean 0.58 ± 0.11), and tear concentrations correlated well with plasma concentrations (r= 0.94). Saliva/plasma ratios ranged from 0.52 to 1.16 (mean 0.79 ± 0.19), and there was a positive correlation between plasma and saliva concentrations (r= 0.84). The mean tear/unbound and saliva/unbound ratio predicted the unbound concentration within 1 &mgr;g/ml in 50 and 78% of the cases, respectively. Saliva and tears have limited clinical value in estimating the unbound concentration of theophylline.

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0163-4356    

出版商:OVID    

年代:1986

数据来源: OVID