Pharmacokinetics - PHARMACOKINETICS Page 1 PK sometimes described as what the body does to a drug refers to the movement of drug into through and out of

Pharmacokinetics - PHARMACOKINETICS Page 1 PK sometimes...

This preview shows page 1 - 3 out of 8 pages.

Page 1 PHARMACOKINETICS PK, sometimes described as what the body does to a drug , refers to the movement of drug into, through, and out of the body the time course of its absorption, bioavailability, distribution, metabolism and excretion (see Drug Excretion ).
Image of page 1
Page 2 DRUG PERMEATION or DRUG UPTAKE It is the passage of drug molecules across biological membranes Process of Uptake of Drug or Drug permeation 1. in between cells (paracellular transport) 2. through cells (transcellular transport) 3. via transporter or carrier proteins a. active transport b. facilitated transport 4. via endocytosis and exocytosis or trancytosis Drug permeation In-between cells Drug Uptake Through Cells It is an aqueous diffusion allowing water soluble, large (abt 30,000Da) and charged drug molecules to pass in between cells It is a lipid diffusion diffusion of lipophilic drugs thru the lipid bilayer Conc. driven a passive diffusion frm high conc. to low conc. Also conc. driven a passive diffusion frm high conc. to low conc. Does not cost the cell energy Does not energy to the cell No competition; so transport of the drug is not limited No competition; so transport of the lipophilic drug is not limited Does not involve the use of aided transport (i.e. carrier transport) Also does not involve the use of aided transport (i.e. carrier transport) Occurs through every biological memb. except thru physiological barriers (Blood-testis barrier, Blood- Brain Barrier) Occurs thru biological membranes including physiological barriers Determined by membrane potential Determined by lipid to aqueous partition coefficient; High lipid to aq. PC favours lipid diffusion Drug permeation via transporters The transporters move molecules into or out of a cell Characteristics a. It is selective ; it can transport only a specific group of drug because of their structure b. There is competition btw drugs of similar structure for uptake by the transporter. So drug uptake is limited c. it is saturable d. E.g. of the transporters ABC (ATP-Binding Cassette) family of transporter esp. p-glycoprotein in the brain, testis and other tissue. it is also used in tumor cells resistant to some chemotherapeutics e. divided into (i) Active transport and (ii) facilitated diffusion Active transport Facilitated Transport a. Not conc. driven ; movt. of molecules occur against a conc. gradient or electrochemical gradient b. It is the MOST RAPID mode of membrane permeation c. it cost the cell energy , making use of Primary transporters (energy-dependent transporters coupled to ATP hydrolysis) and Secondary transporters d. Site of active transport include: Neuronal membranes, Choroid plexus, renal tubular cells, Hepatocytes etc… a. is conc. driven ; movt of molecules is along conc. or electrochemical gradient b. Does not require energy from ATP c. e.g. include movt. of water soluble nutrients into cells (e.g. sugar, a.as, purines, pyrimidine, …) Drug uptake via Endocytosis + Exocytosis (=Transcytosis) A process in which extracellular Macromolecules (MW > 1000) captured
Image of page 2
Image of page 3

You've reached the end of your free preview.

Want to read all 8 pages?

  • Spring '17
  • DR SHITTU
  • Route of administration, Vomiting

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes