Overview of Drug Metabolism Flashcards
What are the four key processes in drug disposition?
Absorption, distribution, metabolism, and excretion (ADME).
Why is drug absorption important?
Adequate drug absorption ensures sufficient concentration of the drug reaches the target tissues to exert its effect.
What factors influence drug absorption?
Factors include physicochemical properties (e.g., solubility, ionization), formulation (e.g., tablet or solution), biological factors (e.g., gut pH, motility), and interactions with food or other drugs.
What are the main routes of drug administration?
Routes include oral, sublingual, rectal, injection (IV, IM, SC), inhalation, topical, transdermal, and application to other epithelial surfaces (e.g., nasal sprays, eye drops).
What is the main site of drug absorption in the GI tract?
The small intestine is the primary site due to its large surface area (~200 m²) and high blood flow (~1 liter/min).
How does lipophilicity affect drug absorption?
Lipophilic drugs (Log P > 0) are absorbed more rapidly via the transcellular route, while hydrophilic drugs (Log P < 0) are absorbed more slowly via paracellular routes.
What is the pH-partition hypothesis?
The hypothesis states that ionization affects drug distribution between compartments with different pH. Weak acids accumulate in high pH environments, and weak bases in low pH environments.
How does pKa influence drug absorption?
Drugs with pKa values allowing partial ionization at physiological pH are better absorbed. Strong acids or bases are poorly absorbed.
What are the effects of protein binding on drugs?
Protein binding reduces drug excretion and pharmacological effect, but it can also prevent drug displacement by other drugs and reduce toxicity.
How can lipophilicity lead to drug accumulation?
Lipophilic drugs can dissolve in adipose tissue, leading to accumulation. This can prolong drug half-life or cause toxicity, especially in individuals with high body fat percentages.
What are the mechanisms of drug absorption?
Mechanisms include passive diffusion, facilitated diffusion, and active transport.
What is the role of first-pass metabolism?
First-pass metabolism occurs in the liver and reduces the concentration of orally administered drugs before they reach systemic circulation.
What is the Henderson-Hasselbalch equation used for?
It calculates the ratio of ionized to unionized drug forms at a given pH, influencing drug absorption across membranes.
What are the advantages of IV drug administration?
IV administration provides rapid drug delivery, avoids first-pass metabolism, ensures 100% bioavailability, and achieves precise control over plasma concentration.
What factors affect GI drug absorption?
Factors include gut pH, motility, bile flow, gut flora, malabsorption states, and food or drug interactions.
