3. Process of drugs in the body (1) absorption ●① absorption of drugs from alimentary canal o oral ingestion is the route of most drugs administration ● Absorption from mouth: gastrointestinal tract epithelium blood o portal circulation liver+systemic circulation
3. Process of drugs in the body ⚫ (1) absorption ⚫ ①absorption of drugs from alimentary canal ⚫ oral ingestion is the route of most drugs administration. ⚫ Absorption from mouth: gastrointestinal tract epithelium in blood ⚫ portal circulation liver systemic circulation
o first pass elimination drug concentration in the blood is declined because metabolism of drugs as a result of passage through the liver and intestine when absorption in the alimentary tract. O rectal administration 50%of the drainage of the rectal region bypasses the portal circulation; thus, the biotransformation of drugs by the liver is minimized It is also useful if the drug induces vomiting, when given orally or the patient is already vomiting
⚫ first pass elimination: drug concentration in the blood is declined because metabolism of drugs as a result of passage through the liver and intestine when absorption in the alimentary tract. ⚫ rectal administration: 50%of the drainage of the rectal region bypasses the portal circulation; thus, the biotransformation of drugs by the liver is minimized. It is also useful if the drug induces vomiting, when given orally or the patient is already vomiting
●② sublingual administration o Placement under the tongue allows the drug to diffuse into the capillary network and therefore to enter the systemic circulation directly. Both the sublingual and the rectal rout have the additional advantage that they prevent the destruction of the drug by intestine and liver enzyme or by low ph in the stomach o parenteral adminstration
⚫ ② sublingual administration ⚫ Placement under the tongue allows the drug to diffuse into the capillary network and therefore to enter the systemic circulation directly. ⚫ Both the sublingual and the rectal rout have the additional advantage that they prevent the destruction of the drug by intestine and liver enzyme or by low pH in the stomach. ⚫ parenteral adminstration
o intravenous injection o subcutaneous injection o intramuscular iniection o intra-arterial injection ① pulmonary absorption o@2 transdermal administration (2)distribution of drugs o Factors influence distribution of drugs
⚫ intravenous injection ⚫ subcutaneous injection ⚫ intramuscular injection ⚫ intra-arterial injection ⚫ ① pulmonary absorption ⚫ ② transdermal administration ⚫ (2) distribution of drugs ⚫ Factors influence distribution of drugs
redistribution Blood vessel fat heart. liver brain pseudoequilibrium
redistribution pseudoequilibrium liver brain fat heart