Absorption Flashcards
(23 cards)
What is drug absorption in pharmacokinetics?
Drug absorption is the process of incorporation of a drug into the bloodstream or the movement of a drug from its site of administration into the central compartment
For which route of drug administration is the absorption process NOT needed?
For the intravenous (IV) route of administration, the absorption process is not needed because the drug is directly introduced into the bloodstrea
Where does absorption occur for oral drug administration?
Absorption from oral administration primarily occurs in the gastrointestinal (GI) tract, especially through the intestinal villi
Where does absorption occur for parenteral (SC, IM) drug administration?
Absorption from subcutaneous (SC) and intramuscular (IM) parenteral routes occurs through continuous capillaries
What is Fick’s First Law of Diffusion in the context of drug absorption?
Fick’s First Law of Diffusion describes that the rate of drug absorption is proportional to the concentration gradient across the membrane and the surface area available for absorption
What is the partition coefficient (P) and how does it relate to drug absorption?
The partition coefficient (P) is the ratio of concentrations of a compound in an organic phase (representing the lipid bilayer) and an aqueous phase (representing body fluids) at equilibrium. A higher P value generally indicates better lipophilicity and, thus, better absorption across cell membranes
Explain the importance of pH in drug absorption.
The pH at the site of administration influences the ionization of weak acid or weak base drugs. Weak acids are more unionized in acidic environments (like the stomach), while weak bases are more unionized in basic environments (like the intestine
How does the ionization state of a drug affect its absorption?
Only the unionized (non-ionized) form of a drug can generally partition across biological membranes, provided it is lipophilic.
What is first-pass metabolism and how does it affect absorption?
First-pass metabolism occurs when orally administered drugs are absorbed from the GI tract, enter the portal vein, and pass through the liver before reaching the systemic circulation. During this process, the drug can be metabolized, reducing the amount of unchanged drug that reaches the bloodstream and thus decreasing bioavailability
What is bioavailability (F)?
Bioavailability (F) represents the fraction of an administered dose of a drug that reaches the systemic circulation in its unchanged form. It can be calculated as F = Fa x Fg x Fh
What is drug reabsorption?
Drug reabsorption is the process of re-incorporation of a drug into the bloodstream from excreting organs. Passive diffusion is the main mechanism for this re-transfer. Examples include reabsorption in the GI tract (gall bladder, large intestine) and the kidney. The pH can also affect the reabsorption of drugs in organs like the kidney.
What are some dosage forms for topical use?
Dosage forms for topical use include cream, lotion, and tinctures
What are the two main categories of solute transport across cell membranes?
Active transport and passive transport.
What are some routes of drug administration where absorption is required?
◦Enteral (Oral, Sublingual, Rectal)
◦Parenteral (Subcutaneous, Intramuscular)
◦Transdermal
◦Inhaled (Pulmonary)
◦Topical
What are some factors affecting drug absorption related to the drug’s properties?
◦pH
◦Partition coefficient (P value)
◦Lipophilicity
◦Solubility
◦pKa
What are the main components typically found in a dosage form?
◦ Active drug component(s), which provide biological effects.
◦ Nondrug component(s), used for stability, desirable color(s)/form(s), and necessary characteristics to deliver the active compound(s).
What is a drug dosage form?
A drug dosage form is the physical form of a drug used to allow for the effective delivery of the active compound to the patient.
Describe active transport. Does it require energy?
Active transport requires ATP hydrolysis or ion gradients to aid the transport of solutes against a concentration gradient. It also requires transporters or carriers
What are some common dosage forms for oral ingestion?
Common dosage forms for oral ingestion include tablets, pills, liquids, and syrup
Describe passive transport. Does it require energy?
Passive transport does not require ATP hydrolysis. It involves the movement of solutes from a compartment with high concentration to a compartment with low concentration
What property of drug molecules significantly affects their rate of diffusion across lipid bilayers in passive transport?
The polarity of drug molecules affects their rate of diffusion across lipid bilayers. Lipophilic (nonpolar) molecules generally diffuse more readily
Which mechanism of solute transport is described as the most important and common route of drug transfer across membranes?
Passive diffusion is the most important and common route of drug transfer across membranes
What are the two types of active transport mentioned?
◦ Primary active transport: ATP-coupled.
◦ Secondary active transport: driven by ion gradients
