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  • Electronic Resource  (7)
  • Column liquid chromatography  (4)
  • NONMEM  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 53 (1998), S. 337-341 
    ISSN: 1432-1041
    Keywords: Key words Amikacin ; Neonate ; Pharmacokinetics ; NONMEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The population pharmacokinetics of amikacin, in neonates, was investigated using the nonlinear mixed effects model (NONMEM). Methods: One hundred and six steady-state amikacin serum levels were obtained from 53 black neonates with a mean gestational age of 35.1 weeks and mean age at the start of treatment of 3.1 days. A one-compartment model was used to fit the data. Results: The final models for clearance (CL) and volume of distribution (V) were: where WT = birth weight (kg) and P = 1.28 for girls and 1.0 for boys. Inclusion of other fixed effect parameters in the model did not significantly improve the fit of the data. The inter-individual variability for CL and V were 18% and 13%, respectively. Intra-individual variability was 29%. Mean (95% CI) values of CL, V and half-life were 0.048 (0.045, 0.051) l· h−1· kg−1, 0.434 (0.414, 0.453) l· kg−1 and 6.4 (6.2, 6.6) h respectively. Conclusion: Birth weight was an important determinant of both CL and V and, in this data set, gender was also found to influence CL. Mean population pharmacokinetic values were within the range of those previously derived for other neonatal populations using traditional methods.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 54 (1998), S. 359-362 
    ISSN: 1432-1041
    Keywords: Key words Carbamazepine ; Population pharmacokinetics ; Children ; NONMEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To derive a model describing carbamazepine (CBZ) clearance in children, in terms of individual patient characteristics. Methods: One hundred and eighteen steady-state serum carbamazepine concentration measurements were gathered during normal routine care of 72 compliant out-patients (2.3–16.3 years old). Levels were obtained from patients receiving monotherapy (55%), concomitant valproate (26%), or concomitant inducers (phenytoin, phenobarbitone; 19%). A one-compartment model was used to fit the data with the computer programme Nonlinear Mixed Effects Model (NONMEM). Results: Weight, age and concomitant medication were all important determinants of clearance. The final model for clearance (l · h−1) was: CL = [0.7(WT)0.4] · M, where WT is patient weight (kg) and M is a scaling factor for concomitant medication, with a value of 1 for patients on CBZ monotherapy or concomitant valproate and 1.4 for those receiving concomitant inducers. For the purposes of this analysis, bioavailability (f) was assumed to be complete, i.e., f is thus included in the term CL. Conclusions: CBZ clearance decreased with increasing age. As age and weight were correlated, either variable was a satisfactory predictor. The influence of both the inducers and valproate on CBZ clearance was as expected. This model, which describes clearance in terms of patient-specific details, can be used when predicting the maintenance dose required to achieve a target mean steady-state CBZ concentration in children.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 48 (1995), S. 381-383 
    ISSN: 1432-1041
    Keywords: Phenobarbitone ; children ; population pharmacokinetics ; NONMEM ; concomitant medication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Non-linear Mixed Effects Modelling (NONMEM) was used to estimate phenobarbitone population clearance values for South African children, using 52 serum levels gathered from 32 patients during their routine care. NONMEM was also used to evaluate the influence of fixed effects such as weight, age and concomitant medication. The final model describing phenobarbitone clearance was CL=[Exp(0.0288 Wt−2.53)] M, where CL=clearance (l·h−1), Exp=the base of the natural logarithm, Wt=patient weight (kg) and M=a scaling factor for concomitant medication with a value of 1 for patients on phenobarbitone monotherapy, 0.62 for those receiving concomitant valproate and 0.87 for those patients receiving concomitant carbamazepine or phenytoin. Mean (95% confidence interval) phenobarbitone clearance values were 7.6 ml·h−1·kg−1 (6.2, 9.0 ml·h−1·kg−1) for the monotherapy group, 5.0 ml·h−1·kg−1 (4.0, 6.0 ml·h−1·kg−1) in the presence of concomitant valproate and 6.8 ml·h−1·kg−1 (5.6, 8.0 ml·h−1·kg−1) in the presence of concomitant carbamazepine or phenytoin. These values are similar to those previously reported from both traditional and NONMEM pharmacokinetic studies.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbidopa and levodopa in plasma ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A validated reversed-phase high-performance liquid chromatographic procedure employing electrochemical detection (LCEC) for the analysis of carbidopa and levodopa in human plasma is reported. The method is sensitive and specific with amperometric detection at a glassy carbon working electrode with Eapp=0.75 V vs. Ag/AgCl. The retention times of levodopa, internal standard, and carbidopa are 3.3, 4.5, and 9.7 minutes, respectively, with an overall chromatographic run time of 12.0 minutes. The peak height ratio versus plasma concentration is linear over the range of 5.0 to 500 ng/mL for each analyte and exhibits correlation coefficients of 0.9957 or better (n=9). The mean absolute recovery of carbidopa and levodopa using the described assay is 36.6 and 66.0%, respectively. The inter- and intra-day accuracy and precision are within 11.8% of the actual values for all concentrations. Also, due to the demonstrated instability of carbidopa and levodopa in plasma a procedure is provided to circumvent this. Blood collected in pre-treated Vacutainer tubes can be stored in an ice bath for up to 4 hours without any significant degradation, thereby providing a practical means for processing several clinical samples simultaneously.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Dipyridamole injection ; Stability studies ; Degradation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The development and subsequent validation of an isocratic high-performance liquid chromatographic (HPLC) procedure employing ultraviolet (UV) detection for the determination of degradation products in Dipyridamole Injection is reported. The development of this assay involved the evaluation of several factors including buffer type, ionic strength, pH, organic composition, and column type. The described method is simple, reproducible, accurate, and selective. The precision, relative standard deviation (RSD), amongst five sample preparations for total degradation products was not more than (NMT) 10.2 %, while the individual degradation products were NMT 12.1%. Intermediate precision, as determined from fifteen sample preparations, generated by two Analysts on different HPLC systems over three days, exhibited an RSD for total and individual degradation products of 8.2 % and NMT 27.5 %, respectively. The mean absolute recovery of dipyridamole using the described method is 102.1±1. 9%, (mean±SD, n=12) over the concentration range of 0.03 % to 5.0 % of its label claim of 5 mg mL−1. The limit of detection and limit of quantitation were 0.1 and 0.3 μg mL−1, respectively. The linearity of the peak response was verified with respect to dipyridamole concentration over a range of 0.3 and 50 μg mL−1 (0.03 % to 5.0 % label claim). The Standard and Assay Preparations are stable for up to 48 hours at room temperature. The selectivity was evaluated by subjecting the finished product (Dipyridamole Injection) to thermal, acidic, basic, oxidative and fluorescent radiation stress conditions. No interference in the analysis of degradation products was observed, showing the method is stability-indicating.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzalkonium chloride ; Tramadol ; Ophthalmic solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic procedure employing ultraviolet detection for the analysis of benzalkonium chloride in 0.5% Tramadol ophthalmic solution is reported. The method requires minimal sample pretreatment and is sensitive, accurate, and reproducible. The peak area versus BAK concentration is linear over the range of 50–150% of its label claim of 0.05 mg/mL. The mean absolute recovery of BAK using the described method is 100.2±1.2%, (mean ±SD, n=10). A stress study with heat, acid, base and UV radiation indicates that the method is stabilityindicating with no interference from drug or degradation products.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 40 (1995), S. 204-206 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stability-indicating method ; 17β-Estradiol-3-phosphate ; Ophthalmic solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic (HPLC) procedure using ultra-violet (UV) detection for the analysis of 17β-estradiol-3-phosphate in an ophthalmic solution is reported. The method is selective, accurate, and reproducible. The peak area versus 17β-estradiol-3-phosphate concentration is linear over the range of 50–150% of its label claim of 1.0 mg/mL, with a detection limit of 20 ng/mL. The mean absolute recovery of 17β-estradiol-3-phosphate using the described method is 99.8±0.6% (mean ±SD, n=10). A stress study with heat, acid, base and UV radiation indicates that the method is stability-indicating with no interference from excipients or degradation products.
    Type of Medium: Electronic Resource
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