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Bioavailability and Granule Properties
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
The elimination rate constant (K) is constant for a drug in normal healthy individuals, and it changes when organs responsible for the elimination of the drug (i.e., kidney and liver) exhibit abnormalities. The absorption rate constant (Ka), on the other hand, depends on the route of administration, the dosage form, and the formulation of a drug. And, for hydrophobic drugs and/or when the absorption and dissolution rate is limited, the faster dissolution is generally reflected in the higher value for the absorption rate constant. Therefore, by changing the formulation of a drug or route of administration, one can alter the peak time and the rate of absorption and time for the onset of action.
Computer Applications in Clinical Pharmacokinetics and Pharmacodynamics
Published in Hartmut Derendorf, Günther Hochhaus, Handbook of Pharmacokinetic/Pharmacodynamic Correlation, 2019
Dennis Mungall, Joe Heissler, Mattieu Kaltenbach
The population methods do not rely on drug concentration or function test information to guide therapy and are the least precise method for estimating individual pharmacokinetic values. Dettli31 originally developed this approach by relating the elimination rate constant for renally cleared drugs to creatinine clearance. By using an estimate of creatinine clearance the patient’s elimination rate could be approximated. Hull and Sarubbi32 applied this approach to aminoglyosides.
The Application of Pharmacokinetic Models to Predict Target Dose
Published in Rhoda G. M. Wang, James B. Knaak, Howard I. Maibach, Health Risk Assessment, 2017
Jerry N. Blancato, Kenneth B. Bishoff
The steady-state blood concentration is monitored as is the elimination profile after exposure ceases. From these data the elimination rate constant would be estimated. Then a model is formulated using Equation 32 for the whole body and Equations 28 and 29 written for the specific organs of toxicological interest. Such a model describes the concentration in the cells of the toxicologically affected organ.
In-vitro and in-vivo evaluation of taste-masked ibuprofen formulated in oral dry emulsions
Published in Drug Development and Industrial Pharmacy, 2021
Haojun Qi, Jiening Dun, Feng Zhao, Xiaodan Qi
The peak plasma concentration (Cmax) and the time required to reach the peak (tmax) were read directly from plasma C–t curve. The area under the curve from zero to 8 h (AUC0–8) was calculated using the trapezoidal rule. The elimination half-life (t1/2) was calculated from the relationship 0.693/k, where k represented the first-order elimination rate constant of the drug which was measured by linear regression of the terminal phase of concentration–time plot. Bioavailabilities for test group and control group were calculated by comparing their AUC0–8. Statistical analysis was performed using analysis of variance (ANOVA). The Student's t-test was used to determine the level of significance, and p < 0.05 was considered statistically significant.
Sulpiride gastro-retentive floating microsponges; analytical study, in vitro optimization and in vivo characterization
Published in Journal of Drug Targeting, 2020
Mahmoud A. Younis, Marwa R. El-Zahry, Mahmoud A. Tallat, Hesham M. Tawfeek
SUL plasma concentration versus time curve was plotted and the pharmacokinetics were calculated as previously reported [1,6,33]. Cmax and Tmax were directly-determined from the curve. The method of residual was adapted to obtain the rate constant of absorption (Kabs). The slope of the terminal linear portion of the curve was used to calculate the elimination rate constant (Kel.) from the linear regression analysis. The apparent half-lives of absorption and elimination (t½) were obtained via dividing 0.693 by the corresponding rate constant. Furthermore, the area under plasma concentration-time curve from zero to end time (AUC0–t) and the area under first moment curve from zero to end time (AUMC0–t) were calculated using linear trapezoidal rule. AUC and AUMC from zero-time to infinity (AUC0–∞ and AUMC0–∞) were calculated by Equations 3 and 4, respectively. t is the last measurable concentration at the end time point (t), Kel. is the elimination rate constant of drug. The mean residence time of the drug in the body (MRT) was calculated using Equation (5).
Toxicokinetics and Biliary Excretion of N-Nitrosodiethylamine in Rat Supplemented with Low and High Dietary Proteins
Published in Journal of Dietary Supplements, 2019
S. E. Kuyooro, J. K. Akintunde, F. C. Okekearu, E. N. Maduagwu
Elimination rate constant represented as Ke is a value used in pharmacokinetics to describe the rate at which a drug is removed from the system (Vugmeyster et al. 2012). It is also equivalent to the fraction of a drug removed per unit time measured at any particular time (Vugmeyster et al. 2012). As shown in the study, rats fed a high-protein diet showed high elimination rate constant of NDEA within a shorter time than the low diatary protein groups. The results of this study suggest that a low-protein diet diminished the rate of elimination of NDEA via bile and increased the half-life of the compound. Recent study showed that carboxylic acids, which are highly protein bound, are extensively excreted in bile with increased elimination rate constant. It was also stated that availability of more proteins for binding accounted for increased elimination rate constant of toxic molecules in the bile of high-protein–fed animals (Singh 2006; Vugmeyster et al. 2012). Conversely, the presence of AFB1 increased the excretion of bound nitrosamines with aflatoxins in the presence of both low and high dietary proteins. The mechanism for this cannot be categorically stated. However, it is likely that the molecular weight of activation complex formed between AFB1 and nitosamines facilitated by the intake of dietary proteins is considerably higher than single nitrosamine. This was supported by the previous study that the toxic compounds having elevated molecular mass were vastly eliminated by bile (Li and Chiang 2015).