Bioavailability absorption

The jejunal perfusion approach generates data which may be used to predict absorption/bioavailability and to establish in vivo-in vitro correlation (IVIVC) even for extended release (ER) products. If a dmg is transported mainly by passive diffusion and has a jejunal Peff higher than metoprolol (1.5 x 10-4 cm s 1 = high-permeability compound), it can be expected to be completely absorbed throughout the small and large intestine [5, 46]. 

Mihaly et al. [127] examined the pharmacokinetics of primaquine in healthy volunteers who received single oral doses of 15, 30, and 45 mg of the drug, on separate occasions. Each subject received an intravenous tracer dose of 14C-prima-quine (7.5 pCi), simultaneously with 45 mg oral dose. Absorption of primaquine was virtually complete with a mean absorption bioavailability of 0.96. Elimination half-life, oral clearance, and apparent volume of distribution for both primaquine and the carboxylic acid metabolite were unaffected by either dose size or route of administration. 

The absorption, bioavailability, and retention of radionuclides in mammals are modified by ... 

Keywords Oral absorption Bioavailability Models of small intestine Intestinal permeability Intestinal perfusion techniques Intestinal versus hepatic first-pass metabolism... 

In the event of dietary Ca abundance, Ca in excess of adequate circulating concentrations is deposited in the skeleton. This occurs to the extent of the body s ability to store Ca, and any excess beyond this threshold is excreted. Accrual of Ca into bone is governed by such factors as dietary intake (including the absorption, bioavailability, utilization of nutrients and minerals, and other dietary constituents that influence absorption or retention), calciotropic hormones, genetic potential, lifestyle factors, life stage, general health, and the adaptive response to physical/mechanical stimuli within the constraints of metabolic economy. 

TABLE 6.5 Summary of studies that investigated the absorption/bioavailability of Ca from CCM ingested as a supplement or food fortificant... 

Table 59-3 Oral Drug Absorption (Bioavailability) of Various Drugs in the Neonate Compared with Older Children and Adults. ...

Table 3.4 Approved dosing regimens and pharmacokinetic parameters related to absorption/bioavailability for therapeutic monoclonal antibodies.

Simulation Simulations exploring the effect of the rate of absorption, bioavailability after an extravascular administration, and the rate of activation/inactivation of the anti-migraine effect were performed. To achieve a response rate of 60% at 2 h, the rate of absorption seems to play a minor role if bioavailability fractions of at least 0.2-0.3 can be achieved and kon is >0.081 ml/ng. At later times after administration, higher values of A0ff are associated with faster offset of the response. 

Absorption/bioavailability The percentage or f raction of a drug that reaches the systemic circulation. Drugs administered by the parenteral route (IV, IM, or SC) are assumed to have 100% absorption, Some drugs administered orally have very good > 80%) and some very poor (< 20%) absorption. The percent absorption most betaken into account when changing from the parenteral to the oral route. Some drugs have such a low bioavailability that to achieve systemic effects they must be administered parenterally. 

Rapid oral absorption (bioavailability 64%) distributes extensively into red blcxxl cells (RBCs)... 

Oral Rate and extent are highly variable and dependent on many factors Maximize compliance (convenient) economical usually safe Absorption (bioavailability) may be erratic and Incomplete... 

Bioavailability/Bioequivalence compcirative studies with generic products to establish bioequivalence— treating with statistical analysis special dose forms (e.g., controlled release products) given with studies of the absorption, bioavailability, steady-state kinetic and, where applicable, metabolism and excretion. 

Nasal absorption of insulin has been of interest since 1983 (Moses et al., 1983). More recent clinical studies tested its long-term acceptability and efficacy in Type-I diabetic patients (Fraumann et al., 1987) and assessed the kinetics of intranasal insulin with a medium-chain phospholipid (Drejer et al., 1990). Nasal irritation was only slight and proportional to the insulin dosage. Compared with subcutaneous injection, intranasal insulin has a quicker onset of action and a much more uniform time course of absorption. Bioavailability was 8-11% and 24% in the meal-relevant period. Further studies, however, are needed before widespread clinical use can be recommended. 

In the context of drug-like substances, hydrophobicity is related to absorption, bioavailability, hydrophobic drug-receptor interactions, metabolism and toxicity. Closely related to log P is the octanol-water distribution coefficient (logDpn), accounting for partition of pH-dependent mixture of ionizable species. Ionization of any compound makes it more water soluble and then less lipophilic. The log D can be calculated from log Pand acid dissociation constant pJC, by the following expression [Cronin, Aptula et al, 2002b Livingstone, 2003] ... 

Pharmacokinetics Absorption bioavailability topical and intramuscular complete oral... 

Stabilizing Agonist Lipid Absorption Bioavailability t 2 Binding... 

The octanol-water partition coefficient, or logP, measures the partition of a compound to between 1-n-octanol and water, which in turn is a model for the propensity of a compound to cross membrane barriers via passive diffusion. Basically. logP is the log ratio of the concentrations of the chemicals in the two solvents. logP = log [0]/[W]. where O is octanol and W is water. In addition. logP is a measure of the hydrophobicity and hydrophilicity of a chemical. Because the hydrophobic parameter is related to absorption, bioavailability, ligand-receptor... 

It is also essential to consider how food is ingested, and the possible effect of combinations of different products. The effect of food proteins on the absorption, bioavailability and in vivo antioxidant activity of fruit and vegetable phenolics may be as important as it was in the case of tea [143]. 

The absorption, bioavailability, and retention of radionuclides in mammals are modified by the age, sex, species, and diet of the organism season of collection the chemical form of the radionuclide in tissue and blood residence time in the digestive tract preferential accumulation by selected organs and tissues and many other variables. 

TABLE 5.1 Physicochemistry and Lipid Permeability Classification of Drug Absorption, Bioavailability, Target Access, and Clearance... 

High absorption but very low bioavailability of oral resveratrol in humans was described [31]. The authors examined the absorption, bioavailability, and metabolism of -resveratrol after oral and intravenous doses in six human volunteers. The absorption of a dietary relevant 25-mg oral dose was at least 70%, with peak plasma... 

The following medicine-related physico-chemical aspects may influence the release and absorption (bioavailability) of an active substance and thereby its final efficacy ... 

Anthocyanins are naturally occurring compounds widespread in plant-derived foodstuffs and therefore abundant in our diet. There are evidences regarding the positive association of their intake with healthy biological effects displayed in vivo. This chapter aims to review some concepts regarding anthocyanins bioavailability. It summarizes the latest advances on the ingestion, absorption, bioavailability, and biotransformation of these compounds through different approaches. Attention is also given to the role of microbiota in anthocyanin metabolism and bioavailability. 

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