Flashcards in PHARM: Drug Absorption, Distribution, and Excretion Deck (21):
What is drug distribution?
The process of binding of a drug to a plasma protein, a tissue compartment, or a receptor site
What is the order (from fastest to slowest) that barbitol, thiopental, hexobarbital, and phenobarbital are metabolized?
Thiopental, barbital, hexobarbital, phenobarbital
What is the partitioning coefficient (Kp)?
What is the effect of oxygen, sulfur, and nitrogen on the partitioning coefficient?
Decreases (makes more hydrophilic)
True or False: Drugs with a higher partitioning coefficient would pass more slowly through a cell membrane.
What does pK represent with regards to drug ionization?
pK is the pH at which a drug will be 50% ionized and 50% non ionized
True or False: If a drug is ionized in a particular biologic fluid, it has a tendency to stay there and accumulate
What is filtration? What limits distribution in this fashion?
Transfer through pores/ fenestrations in capillaries; molecular weight/ size
What mechanisms of drug transport are saturable?
Active transport, facilitated diffusion, receptor-mediated endocytosis
What are the two major routes of drug administration?
Enteral (through the GI) or Parenteral (outside the GI tract)
What are the routes of parenteral drug administration?
Intravenous, intramuscular, subcutaneous, inhalational, transdermal
What are the advantages and disadvantages of IV drug administration?
Advantages- no absorption; attain desired drug concentration more rapidly, can adjust dosage more readily, can administer irritating solutions, bypasses first-pass effect; Disadvantages- risk of infection, pain/difficult self-admin., no drugs that precipitate in blood or oily vehicles
What is the first-pass effect?
The SI and liver contain a lot of the metabolic enzymes that degrade drugs and so enteral administration causes the drug to be exposed to those enzymes before systemic circulation
What is the mechanism by which a drug administered intramuscularly is absorbed?
How can the absorption rate of a drug delivered IM be altered?
Changing muscle to muscle with different flow or by changing the drug vehicle
What method of parenteral drug admin provides slow and constant absorption
True or False: inhalational administration can be for both systemic and local effects?
What are the disadvantages of inhalational drug administration?
Cumbersome administration and difficulty in dosage regulation
What is the transport mechansim by which drugs are absorbed transdermally?
What are the disadvantages of enteral administration?
Gastric irritation, destruction of drugs in GI, irregular absorption, patient cooperation, first-pass effect