and Answers | Newest Updated Study Guide with
Accurate Solutions | Grade A+
• What are the criteria for choosing an effective drug? -✓✓Multiple drugs may be
able to treat a specific condition. You must consult nationally recognized
guidelines for disease management to determine the most effective drug.
• How does hypoalbuminemia affect the process of prescribing? -✓✓Many drugs
that carry an electric charge are bound to albumin in the blood. The distribution of
the drug to target tissues may be affected if hypoalbuminemia is present.
• What is the drug's half-life? -✓✓In clinical practice it takes about four to five
times the half-life for a drugs concentration to read steady state after a drug is
started, stopped or changed. Hal life is the amount of time for a drug to be half
cleared.
• What is meant by the onset of action, peak of action, duration of action of
medications? -✓✓The onset of action is the time between the drug administration
and the time that you see the drugs minimum effect. Onset is the first sign of a
drugs therapeutic effect. Peak of action is the time of the maximum concentration
of the drug in the blood. Duration of action is the onset of action and the
metabolism of the drug below the dose needed for an effect.
• Explain first pass metabolism. -✓✓This occurs when the concentration of the
drug is greatly reduced before it reaches the systemic circulation. It is the portion
of the drug lost during absorption. Generally, occurs in the liver or gut wall. After
a drug is swallowed it is absorbed by the digestive system and enters the hepatic
system. It is then carried by the portal vein to the liver before it reaches the rest of
the body. The liver metabolizes many drugs to such an extent that only a small
portion of the drug reaches the rest of the body. bioavailability of the drug thus is
, greatly reduced by the liver. Sublingual administration can bypass the first pass
system plus it is also faster than oral route.
• What is a steady state? -✓✓The overall intake of a drug is fairly and dynamic
equilibrium with its elimination. Steady state is reached when the time of four to
five times the half-life is reached since the drug had been started.
• What factors affect the drug's absorption? -✓✓Absorption involves several steps.
First the drug must be introduced via route of administration and the form of
medication like tablet or capsule. In IV or IM administration the absorption is less
variable and bioavailability is near 100%. IV administration is considered to lose
no portion of the drug. The fastest route of absorption is inhalation. Drugs must
pass through the epithelial cells of the GI tract to be absorbed by the circulatory
system. Cell membranes may affect the absorption of some drugs because they are
made of lipid bilayers that are semi permeable. This means only small uncharged
solutes can pass through the membrane. Whether or not a molecule is ionized
affects the absorption, since ionic molecules are charged. Solubility favors charged
species. Permeability favors neutral species. Some molecules have special channels
to facilitate movement from the lumen into the circulation. The Henderson
Hasselbeck equation offers a way to determine the portion that is ionized in a given
pH. Weak acids will be present in their nonionic form in the stomach because of
the acidic pH and bases will be in their ionic form. Nonionic species diffuse easier
through cell membranes. Weak acids have a higher absorption rate in the stomach.
The opposite is true in the basic environment of the stomach.
• Identify drug metabolism and the role of the isoenzymes of the P450 system. -
✓✓CYPs are the major enzymes in drug metabolism. Must drugs undergo
deactivation by CYPs are directly facilitated secretion from the body. Many
substances are bioactivated by CYPs to form their active compound. Many drugs
increase or decrease the activity of CYPs isoenzymes either by inducing
biosynthesis of an isozyme, which is enzyme induction or by directly inhibiting the
activity of CYP which is enzyme inhibition. This is a major source of adverse drug
reactions since changes in CYPs activity may affect the metabolism and clearance