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describes action of drugs wihtin body and absorption, [How drugs move in body and how quickly] distrib, metabolism and elimination of drugs in addition to the rate or kinetics at which drug's actions begin and their duration. "ADD ME" (sp?) scheme
looks at how drugs act in the body and deals with [At the site of action, what the drug does] mechanisms of action in addition to the actions of different drug concentrations or doses
rate and extent that the drugs leaves site of administration. a)how long it takes for an oral drug to enter bloodstream from small intestine and how much of the drug makes it. b. bioavailability: [how much of a drug makes it into the bloodstream] what fraction of the dose of a drug reaches its site of actino or a body fluid where the drug has accss to its action.
Factors that affect bioavailability
a. first pass hepatic metabolism: first pass metabolism refers to drugs entering hepatic portal system from intestines, b. drug solubility: very hydrophilic or hydrophobic drugs have difficulty crossing cell membranes and entering most drugs prefer to be hydrophobic and a little hydrophilic so they can pass cell membranes easily., c. chemical instability: some drugs may be affected by stomach's pH or various degradative enzymes in GI tract., d. chemicophysical properties of the drug(suzem salt form)
physiochemical makeup helps determine how easy or difficult drug passes thru membranes (concentration gradient, how lipophilic and surface area of cell)
charge of drug
determine how readily crosses membrane. uncharged chemicals more easily pass membranes. weak acids and bases can be charged or uncharged, but each drug's charge changes based on interaction with body's pH
administration of drugs
administration routes of drugs play large role in drug absorption, 2 major mehtods: a) enteral means thru gastroint tract. b)parenteral: entrance outside of GI tract, usually via injection.
cons of oral/enteral administration
reduced drug absorption, emesis due to gastrointestinal irritation, destruction of some of drug thru enzymatic degradation and gastric acid, inconsisten absorption, and patient compliance issues
Enteral administration. a. enteric coated pills, b.controlled release pills
a)enteric coated allows drug to pass thru stomach without being destroyed by gastric acid. b)controlled release preparation allows drug to release a uniform stream to absorption site over relatively long period of time (disadvantages of this include differences between patients, failure of controlled release causing dose dumping or reduced drug release)other forms of enteral administration
sublingual and rectal administration
(sublingual allows drug to bypass intestines and liver preventing first pass metabolism), rectal(only 50 % of drug enters the liver and is metabolism. disadvantages include irregular and incomplete absorption and irritation of the rectal mucosa)
parenteral administration (a. IV, b. subcutaneous, c. intramuscular, d. intraarterial, e. intrathecal)
a. intravenous: aqueous solution injected into a vein, b. subcutaneous: inject below skin in subc tissues, c. intramuscular into muscles, d. intraarterial: rare b/c makes bleed a ton, e. intrathecal: inject into cerebrospinal fluid of spinal subarachnoid space. OVERALL: parenteral have many advantages over oral admin including more rapid extensive and predictable admin, can be given to unconscious patients. disadvantages include necessity for aseptic protocols/pain/difficult self-med.
the prcoess thru which the drug leaves the bloods tream and enters interstitium (absorption is about intestines, distrib is about bloodstream). 4 aspects: blood flow, capillary permeability, drug structure, degree of binding to proteins
degree of blood flow in brain/liver/kidneys, skeletal muscles and skin, adipose tissues
brain, liver, kidneys have excellent blood flow, skeletal muscles and skin less, adipose tissues even less.
most drugs reversibly bind to plasma proteins. drugs bound to albumin is going to be inactive. albumin is the most common protein in the plasma, albumin keeps blood within the blood vessels. As plasma concentration of the drug increases, more binding occurs.
class I vs class II drugs
clas I: drugs where the dose is less than albumin's capacity to bind (when administered, there will be excess albumin for further binding). class II:given in doses much greater than albumin's ability to bind to it (means there is much more of the drug left over, causing lots of the drug to be free and not to be bound to albumin). if you combine a class I with a class II, free drugs levels of Class I will be much higher, potentially dangerous and may cause overdose situation. Free drugs are active, bound drugs are inert)
Volume of distribution
2/3 in intracellular compartment and 1/3 in extracellular compartment (between cells). Drugs can distrib into any of these compartments dep on size and hydrophobicity of drug. (V(d)=Total amt of drug in body/plasma concentration of drug-->Know: small V(d) indicates drug is primarily sequestered in plasma, a Large V(d) indicates that relatively little of the drug stays in plasma (if mroe than one, more disrib in body and less in bloodstream if less than one, less in body and more in bloodstream, if 1-equal)
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