Drug action absorption

Define objectives of treatment before initiation of a drug Note frequency and severity for a drug Dependant on age, disease, and individual patient factors Include drug action, absorption, elimination, and protein binding Are they clinically significant ... 

Much work has also 4)een done bearing directly or indirectly on the mode of action of quinine and other anti-malarial drugs. The absorption, distribution and metabolism of quinine has been investigated by various workers of whom Kelsey, Ceiling, Oldham and Dearborn (1944)... 

There is a diversity of opinion regarding definitions and benefits of pharmacogenetics and pharmacogenomics.1 3 For example, pharmacogenetics is often considered to be the study of inter-individual variations in DNA sequence related to drug absorption and disposition (pharmacokinetics, PK) or drug action (pharmacodynamics, PD). Polymorphic variation in the genes that encode the functions of transporters,... 

Drug absorption, quantitative models for, PHARMACOKINETICS DRUG ACTION,... 

Goldstein, A., L. Aranow, and S. M. Kalman. 1974. Structure-activity (chapter 1) Drug absorption and distribution (chapter 2). In Principles of Drug Action The Basis of Pharmacology. New York Wiley. 

Advantages of the intramuscular and subcutaneous routes include an increased reliability and precision in the drug blood level Anally achieved and reasonably rapid absorption and onset of drug action. There are, however, serious disadvantages as well. Pain, tenderness, local tissue necrosis (primarily with highly alkaline injections), microbial contamination, and nerve damage may be associated with these forms of parenteral administration. 

Heparin is prescribed on a unit (lU) rather than milligram basis. Tlie dose must be determined on an individual basis. Heparin is not absorbed after oral administration and therefore must be given parenterally. Intravenous administration results in an almost immediate anticoagulant effect. There is an approximate 2-hour delay in onset of drug action after subcutaneous administration. Intramuscular injection of heparin is to be avoided because of unpredictable absorption rates, local bleeding, and irritation. Heparin is not bound to plasma proteins or secreted into breast mUk, and it does not cross the placenta. 

An often-misunderstood principle is that concentration in the blood rises until the rate of absorption equals the rate at which drug is being removed from the body (the so-called peak). This peak does not occur when absorption is complete but rather when the rate of absorption equals the rate of elimination. The time to peak is therefore determined by both absorption and elimination rates in the individual patient. Patients with faster elimination will have earlier peaks than will patients with slower elimination, even when the rate of drug absorption is the same (Fig. 4.2). The extent of absorption is usually expressed as the fraction absorbed or bioavailability. This is an important determinant of drug action. While rate and extent of absorption are related, they are different. In general, the onset and magnitude of effects are related to the rate of absorption, while the average steady state concentrations are related to the extent of absorption. 

Goldstein A, Aronow L, Kalman SM (1968) The absorption, distribution and elimination of drugs — passage of drugs across the placenta. In Goldstein A, Aronow L, Kalman SM ed. Principles of drug action the basis of pharmacology. New York, Harper and Row, p 179. 

The receptor represents the locus of drug action. However, the pharmacokinetic processes of absorption (drug entry), distribution, metabolism, and excretion play principal roles in determining in vivo lime courses and concentrations of drugs and thus modify actions initiated at receptors. 

Specific Physicochemical and Biological Characteristics of Chitosan Useful for Improvement of Drug Action or Enhancement of Drug Absorption... 

While assessing the contributions of alternative scenarios described above is important to understanding the mechanism of drug action, assessing the benefit or risk posed by the overall effect is a slightly different process. With respect to the first case described above, increased phytosterol absorption due to... 

The pharmacokinetic phase of drug action includes the Absorption, Distribution, Metabolism and Elimination (ADME) of the drug. Many of the factors that influence drug action apply to all aspects of the pharmacokinetic phase. Solubility (see Section 3.3), for example, is an important factor in the absorption, distribution and elimination of a drug. Furthermore, the rate of drug dissolution, that is, the rate at which a solid drug dissolves in the aqueous medium, controls its activity when a solid drug is administered by enteral routes (see Section 2.6) as a solid or suspension. 

Absorption , even ofi large moleeules, is quantitative and instantaneous. This is essential ifi drug action is needed immediately. 

The relationship between drug action and the processes of absorption, distribution, and elimination has been successfully applied in clinical pharmacology for the optimisation and individualisation of therapy. In clinical and forensic toxicology, similar relationships are applied in the interpretation of analytical results. 

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