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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.
General toxicology
Published in Timbrell John, Study Toxicology Through Questions, 2017
The values in column 4 above (the residuals) were plotted against time and displayed a linear relationship (see graph page 36). From this graph, was calculated to be . From this the absorption rate constant can be calculated:
A pharmacometric approach to evaluate drugs for potential repurposing as COVID-19 therapeutics
Published in Expert Review of Clinical Pharmacology, 2022
Thanaporn Wattanakul, Palang Chotsiri, Ivan Scandale, Richard M. Hoglund, Joel Tarning
A literature search was performed to identify available pharmacokinetic information of the investigated drugs. If a population pharmacokinetic model was published, the reported structural pharmacokinetic parameters were used for simulations; including absorption parameters (e.g. absorption rate, lag-time, and mean-transit absorption time), elimination clearance, inter-compartmental clearance(s), and volume of distribution(s). Reported inter-individual variability and inter-occasion variability on each structural parameter in the population pharmacokinetic model was also used in the simulation. Additional covariates reported for the population were considered and included in the simulations. When more than one population pharmacokinetic model was available, the model based on a dense sampling schedule and/or a greater number of participants was selected. If a population pharmacokinetic model was not available, results from a non-compartmental pharmacokinetic analysis was used to derive key pharmacokinetic parameters used for simulations; absorption rate constant (approximated by using the time to peak concentration), elimination clearance and total volume of distribution. A one-compartment disposition model with first order-absorption was assumed since compartment-specific parameters are not derived in a non-compartmental analysis. Additionally, an inter-individual variability of 30% was assumed for all pharmacokinetic parameters to reflect an expected population variability.
Tebipenem, the first oral carbapenem antibiotic
Published in Expert Review of Anti-infective Therapy, 2018
Akash Jain, Luke Utley, Thomas R. Parr, Thomas Zabawa, Michael J. Pucci
The pharmacokinetics of TBPM-PI and tebipenem were evaluated in a Phase 2 clinical study in adults with otolaryngologic infection (ME-1211–3) [52]. TBPM-PI was administered in both as 150 mg TID, 250 mg BID or 300 mg TID. The mean pharmacokinetic parameters of the 3 treatment groups were similar between the two studies; absorption rate constant (ka) ranged from 2.51 to 5.64 hr−1. and mean Cmax and AUC0–8 or AUC0–12 of tebipenem in plasma were shown to increase in proportion to dose. The tmax and t½ did not change in proportion to dose.
Formulation optimization and the absorption mechanisms of nanoemulsion in improving baicalin oral exposure
Published in Drug Development and Industrial Pharmacy, 2018
The SPIP study was performed as follows: Rats were first anesthetized with chloral hydrate. After a midline incision was made, about 10 cm of duodenum, jejunum, ileum, and colon were measured with a fine line, and the both ends were intubate with a plastic tube and ligated. The selected segments were washed with physiological saline, attached to the constant-current pump (HL-2 constant-current pump, Shanghai, China) and equilibrated with Krebs-Ring’s solution for 15 min. The flow rate was set at 1.0 mL/min. The animals were maintained constant body temperature, and the incision was covered with gauze soaked in physiological saline. The studied formations (baicalin nanoemulsion and baicalin suspension) were diluted with Krebs-Ringer’s solution to obtain the desired drug concentration (97.66 μg/mL), maintained at 37 °C, and then perfused through intestine for 30 min to obtain a state of equilibrium. At this time, the flow rate was adjusted to 0.2 mL/min. Thereafter, samples were collected every 20 min for 120 min. In the end, the perfused segments were cut out, and the length and inner diameter were measured. Then, 200 μL of the collected perfusion sample was diluted with methanol, sonicated for 30 min, filtered through filter membrane (0.22 μm). After that, the filtrate was measured by HPLC. In SPIP study, the absorption rate constant (Ka) and apparent permeability coefficients (Papp) were used to calculate the drug uptake in the intestine, and the equation was as follows: Cin is the concentration of perfusate solution, Cout is the concentration of collected samples. ΔMin and ΔMout are their weight, Q and V were the flow rate of the inlet solution and volume of perfused segment, R and L were their radius and length.