Comparison of Fluconazole Pharmacokinetics in Serum, Aqueous Humor, Vitreous Humor, and Cerebrospinal Fluid Following a Single Dose and at Steady State

1998 ◽  
Vol 14 (5) ◽  
pp. 459-471 ◽  
Author(s):  
UMAR K. MIAN ◽  
MARTIN MAYERS ◽  
YOGENDER GARG ◽  
QING-FENG LIU ◽  
GIRARD NEWCOMER ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Single Dose ◽  
Steady State ◽  
Aqueous Humor ◽  
Vitreous Humor

Role of active transport of chloride in formation of dogfish cerebrospinal fluid

1960 ◽  
Vol 199 (1) ◽  
pp. 124-126 ◽  
Author(s):  
C. Adrian M. Hogben ◽  
Per Wistrand ◽  
Thomas H. Maren
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Active Transport ◽  
Aqueous Humor ◽  
Extracellular Fluid ◽  
Chloride Concentration ◽  
Potential Difference ◽  
Fluid Formation

A significant steady state or d.c. potential difference exists between the cerebrospinal and extracellular fluids of the anesthetized dogfish. Since the cerebrospinal fluid is negative with respect to the extracellular fluid and the chloride concentration is greater in cerebrospinal fluid, the formation of cerebrospinal fluid must involve at least one process: active transport of Cl–. While acetazolamide abolishes the gradient of chloride between dogfish cerebrospinal fluid and plasma, its administration did not demonstrably change the potential difference. Though the active transport of Cl– is clearly part of the process of cerebrospinal fluid formation, it is probably only part of the process. No potential difference was observed between dogfish aqueous humor and extracellular fluid.

scholarly journals PENETRATION OF RADIOACTIVE SODIUM AND CHLORIDE INTO CEREBROSPINAL FLUID AND AQUEOUS HUMOR

1948 ◽  
Vol 31 (3) ◽  
pp. 259-268 ◽  
Author(s):  
Jun-Ch'uan Wang
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Aqueous Humor ◽  
Ion Concentration ◽  
Exponential Equation ◽  
Rate Of Penetration ◽  
Radioactive Sodium ◽  
Time Required ◽  
Radioactivity Measurements ◽  
Immersion Type

1. Experiments were performed on six dogs to determine the rate of penetration of Cl33 and Na24 across the blood-aqueous humor and blood-cerebrospinal fluid barriers after intravenous injection of the radioactive ions. The radioactivity measurements were made with an immersion type of Geiger-Müller counter. 2. The concentrations of the labelled ions in the anterior chamber and the cisterna magna increase slowly to approach that of plasma. The rate of penetration k is calculated from a simple exponential equation with the half-value interval t0.5 or the time required for the labelled-ion concentration in the fluid to reach 50 per cent of that of plasma. The average t0.5 for Cl38 and Na24 in aqueous humor are 34.3 ± 9 and 27.3 ± 9 minutes, respectively, while those for cerebrospinal fluid are 90 ± 6 and 95 ± 6 minutes, respectively. 3. A study of the radioactivity in plasma was made to determine the per cent remaining after a steady state was reached. By means of this determination the sodium and chloride space was calculated to be 33 ± 5 per cent.

scholarly journals Bio-Distribution and Pharmacokinetics of Topically Administered γ-Cyclodextrin Based Eye Drops in Rabbits

2021 ◽  
Vol 14 (5) ◽  
pp. 480
Author(s):  
Martin Kallab ◽  
Kornelia Schuetzenberger ◽  
Nikolaus Hommer ◽  
Bhavapriya Jasmin Schäfer ◽  
Doreen Schmidl ◽  
...  
Keyword(s):  
Single Dose ◽  
Drug Concentration ◽  
Vitreous Humor ◽  
Controlled Study ◽  
Eye Drops ◽  
Corneal Tissue ◽  
Single Administration ◽  
Local Tolerability ◽  
Dose Administration ◽  
Retinal Tissue

The purpose of this study was to evaluate the ocular pharmacokinetics, bio-distribution and local tolerability of γ-cyclodextrin (γCD) based irbesartan 1.5% eye drops and candesartan 0.15% eye drops after single and multiple topical administration in rabbit eyes. In this randomized, controlled study, a total number of 59 New Zealand White albino rabbits were consecutively assigned to two study groups. Group 1 (n = 31) received irbesartan 1.5% and group 2 (n = 28) candesartan 0.15% eye drops. In both groups, single dose and multiple administration pharmacokinetic studies were performed. Rabbits were euthanized at five predefined time points after single-dose administration, whereas multiple-dose animals were dosed for 5 days twice-daily and then euthanized 1 h after the last dose administration. Drug concentration was measured by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the retinal tissue, vitreous humor, aqueous humor, corneal tissue and in venous blood samples. Pharmacokinetic parameters including maximal drug concentration (Cmax), time of maximal drug concentration (Tmax), half-life and AUC were calculated. To assess local tolerability, six additional rabbits received 1.5% irbesartan eye drops twice daily in one eye for 28 days. Tolerability was assessed using a modified Draize test and corneal sensibility by Cochet Bonnet esthesiometry. Both γCD based eye drops were rapidly absorbed and distributed in the anterior and posterior ocular tissues. Within 0.5 h after single administration, the Cmax of irbesartan and candesartan in retinal tissue was 251 ± 142 ng/g and 63 ± 39 ng/g, respectively. In the vitreous humor, a Cmax of 14 ± 16 ng/g for irbesartan was reached 0.5 h after instillation while Cmax was below 2 ng/g for candesartan. For multiple dosing, the observed Cmean in retinal tissue was 338 ± 124 ng/g for irbesartan and 36 ± 10 ng/g for candesartan, whereas mean vitreous humor concentrations were 13 ± 5 ng/g and <2 ng/g, respectively. The highest plasma concentrations of both irbesartan (Cmax 5.64 ± 4.08 ng/mL) and candesartan (Cmax 4.32 ± 1.04 ng/mL) were reached 0.5 h (Tmax) after single administration. Local tolerability was favorable with no remarkable differences between the treated and the control eyes. These results indicate that irbesartan and candesartan in γCD based nanoparticle eye drops can be delivered to the retinal tissue of the rabbit’s eye in pharmacologically relevant concentrations. Moreover, safety and tolerability profiles appear to be favorable in the rabbit animal model.

Resistance to Outflow of Cerebrospinal Fluid Determined by Bolus Injection Technique and Constant Rate Steady State Infusion in Humans

Neurosurgery ◽  
1985 ◽  
Vol 16 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Michael Kosteljanetz
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Bolus Injection ◽  
Point Of View ◽  
Injection Technique ◽  
Communicating Hydrocephalus ◽  
Constant Rate ◽  
High Degree ◽  
Infusion Technique

Abstract Two methods for the determination of resistance to the outflow of cerebrospinal fluid, the bolus injection technique and the constant rate steady state infusion technique, were compared. Thirty-two patients with a variety of intracranial diseases (usually communicating hydrocephalus) were studied. There was a high degree of correlation between the resistance values obtained with the two methods, but values based on the bolus injection technique were systematically and statistically significantly lower than those obtained with the constant rate infusion test. From a practical point of view. both methods were found to be applicable in a clinical setting.

Single-Dose and Steady-State Pharmacokinetics of Diltiazem Administered in Two Different Tablet Formulations

1992 ◽  
Vol 71 (4) ◽  
pp. 305-307 ◽  
Author(s):  
Lona L. Christrup ◽  
Jan Bonde ◽  
Søren N. Rasmussen ◽  
Jørn Møller Sonnergaard ◽  
Bodil H. Jensen
Keyword(s):  
Single Dose ◽  
Steady State ◽  
Tablet Formulations

Exchange of inulin and dextran between blood and cerebrospinal fluid

1961 ◽  
Vol 201 (6) ◽  
pp. 1145-1148 ◽  
Author(s):  
Arthur R. Rothman ◽  
Emil J. Freireich ◽  
James R. Gaskins ◽  
Clifford S. Patlak ◽  
David P. Rall
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Venous System ◽  
Bulk Flow ◽  
Entry Rate ◽  
Important Means ◽  
Subarachnoid Spaces

C14-labeled inulin (mol. wt. 5,000) and C14-labeled dextran (mol. wt. 12,800 and 77,700) were studied for entry rate into CSF and steady state ratio of drug in cerebrospinal fluid (CSF) to drug in plasma, in nephrectomized dogs. For all three of these compounds the entry rates and steady state ratios were very similar. Exit rates of C14-inulin and C14-dextran (mol. wt. 77,700) were studied in nephrectomized and nonnephrectomized dogs. The exit rates were rapid and very similar for the two compounds. Acetazolamide increased the steady state ratio and decreased the exit rates significantly. These data suggest the presence of leaks in the blood CSF barrier of at least 60 A in diameter and indicate that bulk flow of CSF from the subarachnoid spaces to the venous system is an important means of exit of substances present in the CSF. Compounds which enter the CSF slowly fail to achieve diffusion equilibrium because of their relatively rapid exit by means of bulk flow.

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