Search PubMed⌕ Search

Biomedical subjects

K Chiba

Publications and source records attributed to K Chiba.

At least 451 records · Page 25Linked to original sources
PubMed1981

[Analysis of RIA standard curve by log-logistic and cubic log-logit models (author's transl)].

In order to improve goodness-of-fit in RIA standard analysis, programs for computing log-logistic and cubic log-logit were written in BASIC using personal computer P-6060 (Olivetti). Iterative least square method of Taylor series was applied for non-linear estimation of logistic and log-logistic. Here "log-logistic" represents Y = (a--d)/(1+log(X)/c)b)+d As weights either 1, 1/var(Y) or 1/sigma 2 were used in logistic or log-logistic and either Y2(1--Y)2, Y2(1-Y)2/var(Y), or Y2(1--Y)2/sigma 2 were used in logistic or log-logistic and either Y2(1--Y)2, Y2(1--Y)2/var(Y), or Y2(1--Y)2/sigma 2 were used in quadratic or cubic log-logit. The term var(Y) represents squares of pure error and sigma 2 represents estimated variance calculated using a following equation log(sigma 2 + 1) = log(A)+J log(y). As indicators for goodness-of-fit, MSL/Se2, CMD% and WRV (see text) were used. Better regression was obtained in case of alpha-fetoprotein by log-logistic than by logistic. Cortisol standard curve was much better fitted with cubic log-logit than quadratic log-logit. Predicted precision of AFP standard curve was below 5% in log-logistic instead of 8% in logistic analysis. Predicted precision obtained using cubic log-logit was about five times lower than that with quadratic log-logit. Importance of selecting good models in RIA data processing was stressed in conjunction with intrinsic precision of radioimmunoassay system indicated by predicted precision.

Computers↗
PubMed1981

Pharmacokinetics and relative bioavailability of intramuscular phenobarbital sodium or acid in infants.

Phenobarbital pharmacokinetics after a single intramuscular dose of approximately 10 mg/kg of phenobarbital sodium or acid were studied in twelve infants with febrile convulsions. The mean peak time after phenobarbital sodium (0.92 hr) was significantly (p less than 0.01) shorter than that after phenobarbital acid (5.83 hr), whereas the mean peak levels (16.2 vs 13.8 microgram/ml) did not reach statistical difference (p less than 0.2) between both dosage forms. The values of the absorption rate constant and the area under the curves calculated from 0- to up to 6-hr periods were significantly higher (P less than 0.001 to 9.005) after the sodium form. There were no significant differences in such parameters as t1/2, Vd/F, and C1/F between the two preparations. The overall mean values of these variables were: t1/2, 64.0 hr, Vd/F, 0.667 1/kg, and C1/F, 0.136 m1/min/kg. Some delay in rising phenobarbital concentration in cerebrospinal fluid (CSF) as compared with that in plasma after phenobarbital sodium was observed, though the absolute values of phenobarbital concentrations in CSF were similar from both dosage forms around the time when peak plasma levels were attained.

Biological Availability↗
PubMed1980

Pharmacokinetics of ketoprofen following single oral, intramuscular and rectal doses and after repeated oral administration.

The pharmacokinetics of ketoprofen was studied in the same healthy subjects after single oral, intramuscular and rectal doses, and after repeated oral administration. No significant difference in the mean t1/2 (1.13-1.27 h) was observed after the different modes of administration. The mean [AUC] 0 infinity after rectal administration of a suppository showed the minimum significant difference (p < 0.05) from that after oral administration of the capsule. The apparent volume of distribution (Vd/F) was approximately 10-15% of body weight. The renal contribution (mean, 0.10-0.15 ml/min/kg) to the plasma clearance of free ketoprofen was assumed to be, at most, 8.3-12.9%. The projected cumulative excretion of total (free plus conjugated) ketoprofen via urine exceeded 63-75% of the dose, of which approximately 90% was ketoprofen glucuronide. A mean of 71-96% and 73-93% of the oral capsule was estimated to be systemically available after administration of the intramuscular preparation and rectal suppository, respectively. In four of seven subjects, CPK concentration was elevated after the intramuscular injection. The mean steady-state concentration of ketoprofen in plasma ranged from 0.43 to 5.62 microgram/ml after the final dose of a 50 mg q. i. d. regimen. The disposition data and plasma levels observed at steady-state were in agreement with those predicted from the single oral dose study. The accumulation ratio was 1.08 +/- 0.08. The results suggest that the rectal suppository can be recommended as an extravascular mode of administration of this drug.

Administration, Oral↗
PubMed1980

Michaelis-Menten pharmacokinetics of diphenylhydantoin and application in the pediatric age patient.

Michaelis-Menten pharmacokinetics were evaluated for diphenylhydantoin given to 104 patients 0.5 to 16 years of age with seizures. A method for individualizing the dosage regimen of DPH for each patient was evaluated retrospectively. The Vmax was inversely related to age (r = 0.552, P less than 0.001) but there was no such relationship for Km. The individual pharmacokinetics were characteristic of that person and could be used to adjust dosage so that toxicity would be avoided. We present a nomogram for adjusting the dosage of DPH in the pediatric age groups.

Adolescent↗
PubMed1980

Apparent Michaelis-Menten kinetic parameters of phenytoin in pediatric patients.

In a retrospective study of 104 pediatric patients (0.5-16 yr) with seizures, the effects of concurrently administered anticonvulsants on Michaelis-Menten kinetic parameters of phenytoin were investigated. Individual kinetic parameters (Km and Vmax) for phenytoin were estimated from at least two reliable steady-state plasma concentration and dose data. Km tended to increase and to become more variable as the number of coadministered anticonvulsants increased. Significant difference was found in a group of patients taking three or more coadministered anticonvulsants. On the contrary, Vmax was not affected by those drugs in the higher age groups. Additive inhibitory rather than inductive effects of commonly used anticonvulsants appeared likely to cause an increase in Km. These observations suggest that dosage regimen adjustment of phenytoin based on the averaged Vmax in a given pediatric age group rather than the Km is recommended for a particular patient with inadequate therapeutic control of seizure or toxicity of this drug.

Adolescent↗