Preparation for Child Psych PRITE and Boards
Revision as of 18:55, 22 August 2011 by Eugene Grudnikoff MD (Talk | contribs) (Absorption)

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Introduction

Although our website is oriented toward child and adolescent psychiatry, this review of drug metabolism will not be limited to pediatric topics. The subject matter is very important for all doctors and is extensively tested on PRITEs and Boards. Child-specific considerations will be addressed in a dedicated section below.

Absorption

Absorption is the process of getting the drug into the bloodstream.

Bioavailability, a subcategory of absorption, is fraction of medication that reaches systemic ciculation. Absorption of PO medications takes place in the GI tract, maily in the small intestine, and thus affected by a number of factors:

  • GI tract conditions (acidity, presence of food, chronic inflammation, gut flora, acute diarrhea or emesis, gastric emptying rate)
  • Physcial properties of the drug (pKa, solubility, hydrophobicity)
  • Presence of specific drugs and foods that interact with the medication
  • First-pass metabolism (may vary significantly from person to person)

Bioavailablity of IV medications is by definition 100%.

Pharmacodynamics

CYP450