Drug effects absorption

Increasing the gastric pH, which causes a decrease in absorption of weakly acidic drugs and results in a decreased drug effect (eg, digoxin, phenytoin, chlorpromazine, and isoniazid)... 

In attempts to improve the oral activity of norfloxacin, prodrug techniques have been employed. In an initial approach, the (5-methyl-2-oxo-l,3-diox-4-yl)-methyl group, which had been shown previously to be effective in a novel ampicillin prodrug, was investigated as a promoiety [ 109]. However, although the ester (77) liberates norfloxacin in the presence of mouse blood, after oral administration to mice, it was found that the blood levels of norfloxacin achieved are lower (approximately with respect to Cmax) than those achieved upon oral administration of an equimolar dose of norfloxacin, itself. This observation has been assumed to be due to an instability of this ester prior to absorption rather than an inability to liberate the parent drug after absorption. 

Blodinger, J. (1982). Formulation of Veterinary Dosage Forms. Marcel Dekker, New York. Borowitz, J.L., Moore, P.F., Yim, G.K.W. and Miya, T.S. (1971). Mechanism of enhanced drug effects produced by dilution of the oral dose. Toxicol. Appl. Pharmacol. 19 164-168. Brandau, R. and Lippold, B.H. (1982). Dermal and Transdermal Absorption. Wissenschaf-tliche, Verlagsgesellschaft mbH, Stuttgart. 

The following sections provide an overview of the application of the IPL for the study of drug absorption. Examples are provided to illustrate the use of the IPL to study drug permeability, absorption profiles, transport mechanisms and the effects of inhaled dose formulation on drug disposition. 

Transderm al Easy Convenient No first-pass metabolism Local or systemic effects Irritation Potent drugs only Absorption affected by site of application Hard to administer Solutions, lotions, sprays, gels, ointments, creams, powders, patches... 

Together, the chemistry of codeine and the drug s absorption into the bloodstream, distribution to various compartments and tissues in the body, metabolism (breakdown of the parent compound into smaller molecules, or metabolites), and excretion are intimately related to how codeine exerts its medicinal or therapeutic effects. Codeine s chemical properties and pharmacologic characteristics explain how, figuratively speaking, a spoonful of codeine can relieve pain, suppress cough, or act as an antidiarrheal. 

Food effect, absorption of most psychotropic drugs is not significantly affected by concomitant intake of food. An exception is buspirone, with a twofold increase of absorption with food intake... 

Pharmacokinetics is defined as the study of the quantitative relationship between administered doses of a drug and the observed plasma/blood or tissue concentrations. The field of pharmacokinetics is concerned with drug absorption, distribution, biotransformation, and excretion or elimination. These processes, in addition to the dose, determine the concentration of drug at the effector or active site and, therefore, the intensity and duration of drug effect. 

For many poorly soluble drugs, the dissolution rate best reLects the bioavailability of the compound (Juncher and Raaschou, 1957 Benge et al., 1977). Indeed, solubility might affect absorption only to the extent that it affects the dissolution rate. Since absorption is a dynamic process, the solubility of a drug might be of limited consequence if the absorption rate is so rapid that solubility is not attained in the biological Luid. The dissolution rate in this instance would be critical since it could establish the effective absorption rate (Berge et al., 1977). 

Pharmacokinetics (PK) is the science that describes the time course of a circulating drug concentration in the body resulting from administration of a certain drug dose. In comparison, pharmacodynamics (PD) is the science that describes the relationship of the time course of drug concentration and the drug effects in the body (Meibohm and Derendorf, 1997). Key determinants of the PK of a drug include absorption, distribution, metabolism, and elimination (ADME) (Lin et al., 2003), as discussed in Chapter 1. 

Surfactants have been the most investigated chemicals to promote drug absorption from all body tracts. In this section, we will focus on work carried out from the early stages on the enhancing effects of surfactants on drug GI absorption as well as on their interactions with the GI membrane and their toxicity. Systems with multifactorial effects such as emulsions and microemulsions are not the focus of this review. 

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