QUESTIONS AND CORRECT ANSWERS
▶ Most absorption occurs in the...? Answer:small intestine.
• Rapid GI motility may speed the drug without complete absorption.
• Slow motility may cause the drug to be retained in the stomach where it is
exposed long to destructive enzymes and stomach acid.
• Fatty food slow drug absorption. Absorption is most complete between
meals, full stomach may lessen nausea but slows absorption.
▶ For a drug to be absorbed there must be...? Answer:Be adequate blood
flow. Therefore drugs are absorbed faster where blood flow is high. Large
muscles have high blood flow which maximize absorption.
▶ Distribution? Answer:Movement of pharmacologic agents throughout the
body after they are absorbed
▶ The simplest factor in determining drug distribution.? Answer:The
amount of blood flow to the body tissues. Heart, liver, kidneys receive
greatest % of blood flow so these organs receive the highest exposure to
absorbed drugs. Skin, bone and adipose tissue receive little blood flow.
▶ Drug solubility? Answer:Lipid solubility determines how quickly a drug is
absorbed, mixes in the blood stream, crosses membranes, and becomes
localized in body tissues.
▶ Are lipid soluble drugs more distributed to the body tissues??
Answer:Yes-they are not limited by barriers that water soluble drugs are so
thus they are more distributed by body tissues.
▶ Protein binding? Answer:Many drugs bind reversibly to plasma proteins
to form drug-protein complexes which are too large to cross capillary
membranes. The drugs the continue circulation in the bloodstream and are
unavailable for distribution to their site of action. Drugs remain trapped in
the bloodstream until they are released or displaced. Only unbound or free
drugs can reach their target cells or be excreted by the kidneys.
, ▶ Metabolism? Answer:Also known as biotransformation is the process
used by the body to chemically change a drug molecule. • Prodrug- Agents
that require metabolism to produce their action. Ex: enalapril (vasotec) is
converted in the liver to enaliprat which has more of an effect on lowering
blood pressure than the original drug.
▶ Role of enzymes/factors that impact metabolism? Answer:Most
metabolism in the liver is accomplished by the hepatic microsomal enzyme
system. (P450 system named after cytochrome P450 (CYP) which is a key
component of the system.)
▶ First pass effect? Answer:Mechanism whereby drugs are absorbed,
enter into the hepatic portal circulation, and are inactivated by the liver
before they reach the general circulation.
▶ Excretion? Answer:Drugs will continue to act on the body until they are
either metabolized to an inactive form or removed from the body by
excretion.
▶ The therapeutic response? Answer:Of most drugs depends on their
concentration in the plasma.
▶ Therapeutic range? Answer:is the range in which the drug produces its
desired therapeutic action.
▶ Duration of action? Answer:The length of time a drug concentration
remains in the therapeutic range
▶ Plasma half-life? Answer:The length of time required for the plasma
concentration of a drug to decrease by on half after administration. As a
rule of thumb, when a drug is discontinued it takes approximately four half-
lives before the agent is considered "functionally" eliminated.
▶ Loading dose? Answer:Is a higher amount of drug, often given only once
or twice, that is administered to "prime" the bloodstream with a level
sufficient to quickly induce a therapeutic response. Before plasma levels
drop back toward zero, intermittent maintenance doses are given to keep
the plasma drug concentration in the therapeutic range.