摘要:

Clinical Pharmacology and Therapeutics(1994)55,247–248; doi:10.1038/clpt.1994.

ISSN:0009-9236    

DOI:10.1038/clpt.1994.23

年代:1994

数据来源: WILEY

摘要:

Clinical Pharmacology and Therapeutics(1994)55,249–255; doi:10.1038/clpt.1994.

ISSN:0009-9236    

DOI:10.1038/clpt.1994.24

年代:1994

数据来源: WILEY

摘要:

Clinical Pharmacology and Therapeutics(1994)55,255–255; doi:10.1038/clpt.1994.

ISSN:0009-9236    

DOI:10.1038/clpt.1994.25

年代:1994

数据来源: WILEY

摘要:

We studied the influence of cytochrome P450 2D6 (CYP2D6) on the steady‐state disposition kinetics and the electrocardiographic effects of flecainide at two doses and during combination with amiodarone. Seven extensive and five poor metabolizers of dextromethorphan were studied during a three‐period crossover study. All subjects received 50 mg flecainide every 12 hours, alone or together with 200 mg amiodarone every 12 hours, and 100 mg flecainide every 12 hours for 5 days. Mean steady‐state plasma concentration of flecainide and QRS change from predrug value did not differ significantly among extensive and poor metabolizer subjects during each study period. Except for a shortened elimination half‐life and nonlinear kinetics in extensive metabolizer subjects, phenotype had no significant influence on flecainide pharmacokinetics. Combination with amiodarone resulted in an increase in mean flecainide plasma concentration and effect in subjects with both phenotypes. Our findings indicate that CYP2D6 phenotype predicts flecainide nonlinear kinetics and flecainide half‐life but has no influence on electrocardiographic effects during repeated administration of flecainide or on the extent of the amiodaroneflecainide interaction.Clinical Pharmacology and Therapeutics(1994)55,256–269; doi:10.1038/

ISSN:0009-9236    

DOI:10.1038/clpt.1994.26

年代:1994

数据来源: WILEY

摘要:

The pharmacokinetics of (+)‐methylphenidate after oral administration of 20 mg racemic methylphenidate hydrochloride and the relationship between clinical effects of plasma (+)‐methylphenidate concentration were investigated in 15 patients with hypersomnia and four healthy volunteers. The elimination half‐life of (+)‐methylphenidate in patients was within the range of 2.6 to 3 hours, and the time to reach the peak concentration ranged from 1 to 3 hours. The values of half‐life and time to reach the peak concentration in the patients were almost the same as the values in healthy subjects. The plasma (+)‐methylphenidate concentration profiles after repeated administration of racemic methylphenidate were similar to those after single administration. No correlation was observed between the plasma (+)‐methylphenidate concentration and the subjective sleepiness as measured by Stanford Sleepiness Scale. On the other hand, a significant correlation was found between the sleep latency as measured by the multiple sleep latency test and the plasma concentrations of (+)‐methylphenidate (r= 0.850). The time course of the sleep latency after repeated administration was similar to that after single administration. The sleep latency of more than 10 minutes was achieved by maintaining the plasma (+)‐methylphenidate concentrations above 3 ng/ml.Clinical Pharmacology and Therapeutics(1994)55,270–276; doi:

ISSN:0009-9236    

DOI:10.1038/clpt.1994.27

年代:1994

数据来源: WILEY

摘要:

A study of choline pharmacokinetics was undertaken in four patients receiving long‐term total parenteral nutrition. On consecutive days, 7, 14, 28, and 56 mmol choline chloride were intravenously infused over a 12‐hour period in each subject. The choline concentration was determined in plasma at baseline, ¼, 1, 3, 6, and 12 hours, and 3 and 12 hours after the infusion ended, and in daily 24‐hour urine collections. Analysis of variance showed the data fit a two‐compartment model in which elimination from the central compartment was saturable significantly better than a one‐compartment model in all four subjects (p<10−8in all cases), and significantly better than a nonsaturating model in three of the four subjects (p= 1.0 × 10−9, 7.5 × 10−6, 9.4 × 10−11, respectively). The model allowed estimates of the rate constant for choline elimination at ambient levels, first‐order rate constants for transfer between central and peripheral compartments, the dissociation constant for the saturable elimination process, the apparent volume of distribution in the central compartment, the steady‐state volume of distribution, and the quantities of choline in the central compartment and in the readily exchangeable pool.Clinical Pharmacology and Therapeutics(1994)55,277–2

ISSN:0009-9236    

DOI:10.1038/clpt.1994.28

年代:1994

数据来源: WILEY

摘要:

The pharmacokinetic profiles of 0.3% ofloxacin and 0.3% tobramycin ophthalmic solutions after multiple administrations in the eyes of 160 healthy volunteers were evaluated. In human tears, ofloxacin and tobramycin were found to have terminal half‐lives of 226 and 154 minutes, respectively. The mean residence time in the ocular tear fluid was 326 minutes for ofloxacin and 106 minutes for tobramycin. The mean duration of time that ofloxacin remained above the MIC90value for five bacterial species evaluated was 605 minutes, compared with 251 minutes for tobramycin. The mean area under the inhibitory curve for the five bacterial species evaluated was greater for ofloxacin (2224) compared with tobramycin (1549). The duration of time above the MIC90for ofloxacin was longer compared with tobramycin for gram‐positive isolates. Overall, the pharmacokinetic and pharmacodynamic profiles of ofloxacin were superior to those of tobramycin for most parameters studied.Clinical Pharmacology and Therapeutics(1994)55,284–292; doi:10.1038/clpt.1

ISSN:0009-9236    

DOI:10.1038/clpt.1994.29

年代:1994

数据来源: WILEY

摘要:

We studied the oxidative andN‐acetylator caffeine metabolic profile in 107 healthy Spanish volunteers. Smokers had significantly higherN‐1‐andN‐3‐demethylations activities than nonsmokers (p= 0.03 andp= 0.02, respectively), and the three caffeine demethylations indexes were strongly correlated with each other (r>0.7;p<0.001). Our in vivo studies suggest that CYP1A2 is involved, at least in part, in the primaryN‐demethylations of caffeine. A non‐normal and possibly bimodal distribution was detected in the xanthine oxidase activity (p= 0.04), with about 4% of subjects deficient of this metabolic activity. The population exhibited a trimodal distribution of acetylator phenotype determined by use of the 5‐acetylamino‐6‐amino‐3‐methyluracil/1‐methylxanthine ratio (normality test;p= 0.004). Seventy subjects (65.4%) were phenotyped as slow acetylators. The mutated gene frequency was 0.81, which is similar to other white populations.Clinical Pharmacology and Therapeutics(1994)55,293–3

ISSN:0009-9236    

DOI:10.1038/clpt.1994.30

年代:1994

数据来源: WILEY

摘要:

Potential interactions between the nonsteroidal anti‐inflammatory etodolac and the anticoagulant warfarin were studied in 18 healthy subjects by use of a randomized, three‐period crossover design. Each treatment lasted 2½ days and consisted of warfarin, etodolac, or both drugs. Prothrombin time was determined daily during each warfarin period to measure pharmacologic effect. Total serum concentration and unbound fraction of both drugs were determined over the dose interval after the last dose of the study drug(s). Concomitant etodolac did not affect the prothrombin time response or the unbound clearance of warfarin. During concomitant etodolac administration, the median peak concentration of total warfarin was significantly decreased by 19% (p= 0.005), median total clearance was significantly increased by 13% (p= 0.0123), and the unbound fraction tended to increase (median unbound fraction of warfarin, 1.245% with etodolac and 1.045% without etodolac;p= 0.0979; not statistically significant). These observations suggest a small displacement of warfarin from serum protein by etodolac or a metabolite of etodolac. No etodolac pharmacokinetic parameter was significantly affected by concomitant warfarin administration. Thus etodolac does not appear to alter the unbound clearance of warfarin or augment its pharmacologic effect. Nevertheless, it is prudent that clinical monitoring be done for individuals taking these two compounds concomitantly.Clinical Pharmacology and Therapeutics(1994)55,305–316; doi:10.1038/clpt.

ISSN:0009-9236    

DOI:10.1038/clpt.1994.31

年代:1994

数据来源: WILEY

摘要:

Quinine‐induced reversible hearing impairment at the frequencies of 1000 and 2000 Hz was investigated in healthy volunteers to analyze the plasma concentration‐effect relationship of the drug. Six subjects were given two identical oral doses of quinine and a constant rate infusion of quinine over 6 hours (15 mg · kg−1) on three separate occasions. A simple pharmacodynamic model, E = k · Cγ(in which E is effect, k is a proportionality constant, C is drug concentration, and the exponent γ is a fitting parameter), was found to describe well the relationship between hearing impairment and quinine concentrations in a hypothetical effect compartment. No statistical differences were found in the estimated parameters when the three dosings were compared, indicating that quinine‐induced hearing impairment is independent of route of administration. The first‐order rate constant (keo), linking plasma concentrations to the concentrations in the effect compartment, was (mean ± SD) 0.71 ± 0.19 and 0.99 ± 0.37 hr−1for 1000 and 2000 Hz, respectively. The corresponding values of k were 0.15 ± 0.10 and 0.12 ± 0.19 and the values of γ were 2.13 ± 0.57 and 3.44 ± 1.04 for 1000 and 2000 Hz, respectively. Effect was also analyzed by semiparametric pharmacodynamic modeling, which gave results comparable to those obtained with the link model. We conclude that a simple power function is a reliable pharmacodynamic model for describing quinine‐induced hearing impairment in healthy subjects.Clinical Pharmacology and Therapeutics(1994)55,317–3

ISSN:0009-9236    

DOI:10.1038/clpt.1994.32

年代:1994

数据来源: WILEY