Absorption, drugs definition

Answer A. The key word is absorption. By definition, IV injection does not involve absorption processes because drug is injected directly into the systemic circulation (choice B is wrong). All of the other modes of administration are associated with absorption. The mhalational mode is the most rapid because of the great area of the absorptive surface and the close proximity to the blood. 

The overall objective of clinical trials is to establish a drug therapy that is safe and effective in humans, to the extent that the risk-benefit relationship is acceptable. The ICH process has developed an internationally accepted definition of a clinical trial as Any investigation in human subjects intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of one or more investigational medicinal product(s), and/or to identify any adverse reactions to one or more investigational medicinal product(s) and/or to study absorption, distribution, metabolism and excretion of one or more investigational medicinal product(s) with the object of ascertaining its (their) safety and/or efficacy. ... 

Whenever a drug is administered by an extra-vascular route, there is a danger that part of the dose may not reach the blood (i.e., absorption may not be complete). When the intravenous route is used, the drug is placed directly in the blood therefore an IV injection is, by definition, 100% absorbed. The absolute bioavailability of an extravascular dosage form is defined relative to an IV injection. If IV data are not available, the relative bioavailability may be defined relative to a standard dosage form. For example, the bioavailability of a tablet may be defined relative to an oral solution of the drug. 

Pharmacokinetic Definition of Intestinal Absorption (fa), Presystemic Metabolism (Ec and Eh) and Absolute Bioavailability (F) of Drugs Administered Orally to Humans... 

Definition ofi Absorption and Bioavaiiabiiity of Drugs following Oral Administration... 

Definition of Absorption and Bioavailability of Drugs following Oral Administration 499... 

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,... 

Oral bioavailability is one of principal pharmacokinetic properties in drug discovery. It represents the percentage of an oral dose that is available to produce pharmacological actions, in other words, the fraction of the oral dose that reaches the system circulation in an active form. By the definition, when a drug is administered intravenously, its bioavailability is 100%. However, when a medication is administered via other routes, especially orally, its bioavailability decreases due to incomplete absorption and first-pass metabolism. 

In its broadest terms the discussion of HPLC detection for chiral species must include the analysis of mixtures with achiral substances as well as the quality testing of, for example, the enantiomeric purity of a chemically pure drug form. The distinction between the definitions of chemical purity versus optical purity can not be overemphasized. In an efficient chiral HPLC system the latter problem is trivial, and if retention times are significantly different then any conventional detector such as RI, electrochemical, absorption, etc., could be used. Co-elutions are a major experimental concern in separations of mixtures and at this juncture it is not only prudent but absolutely necessary to involve a chiroptical detector to preferentially identify the chiral analyte. 

The logarithmic expression in the definition of AP has no physicochemical basis and is used for numerical reasons only pH= 6.5 was selected as the representative pH of small intestines, where most of the absorption of drugs takes place. The incorporation of the terms Pc and fun in the numerator of (6.2) means that the pH-partition hypothesis governs gastrointestinal absorption. Plausibly, AP was considered proportional to solubility and inversely proportional to the dose in accord with classical dissolution-absorption considerations. The volume term V corresponds to the small-intestinal volume content, which was set arbitrarily... 

Bioavailability studies quantify rate and extent of absorption. They compare the efficiency of the disposition of several drug formulations, e.g. immediate-release vs. extended-release or capsule vs. tablet or tablet A vs. tablet B etc., or they compare the disposition of different routes of administration, e.g. oral vs. subcutaneous or oral vs. intravenous. According to the definition, a comparison to the intravenous bolus injection yields the absolute bioavailability. 

The hygroscopicity of a drug and pharmaceutical substances is a potential parameter to be considered in tablet formulation. The moisture uptake rate is quite variable depending on the type of drug and excipients as well as the environmental conditions. So, a concise definition of hygroscopicity is not possible. Powders can absorb moisture by both capillary imbibition and swelling. The instantaneous water absorption prosperties of pharmaceutical excipients correlate with total surface area while the total absorption capacity correlates with powder porosity [22],... 

Schedule for medication administration. Patients must be made aware of appropriate intends between drug doses. Timing of administration may affect absorption and blood or ocular levels of the drug. Clinicians should provide verbal definition of label instructions (e g., before meals, after meals, at bedtime two, three, or four times daily every 4,6, or 12 hours on an empty stomach). As directed is considered an inappropriate form of patient instruction. 

---