PHAR 315 Lecture Notes - Lecture 1: Therapeutic Index, Drug Metabolism, Choroid Plexus
23 Feb 2016
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Physiochemical properties of the drug (phase at rt, mw, if they are a protein, lipid, hormone, or carb) determine absorption/distribution. Absorption/distribution may dictate or be affected by route of administration (roa) Roas = po, iv, im, ip (intra peritoneal), sub q (sub cutaneous), intra-nasal, inhalation, transcutaneous/transdermal, epidural, sl, pr, pessary (vaginal device), intrathecal (into the spine) When the absorbed drug passes through the liver before distribution = substantial metabolism of the drug roas such as sl, intra-nasal, pr, and epidural avoid this. When drug concentrations equilibrate on either side of a membrane, there is no driving force for the drug to move across. In the body elimination of the drug is always happening, so there is always a concentration gradient. We can use ph differences (i. e. in the blood and urine) to drive the drug across the membrane. Ionized drugs cannot (usually) cross membranes, but are water soluble. When the drug moves through water compartments (i. e. cytosol, interstitial space).
