Pharmacology Exam I: Terms and Concepts

PO drugs have three phases, name them.
1. pharmaceutic
2. pharmacokinetic
3. pharmacodynamic

SubQ, IM, and IV go through which two phases.
1. pharmacokinetic
2. pharmacodynamic

Define parmaceutic phase.
The phase in which tablets are disintegrated (broken down) and dissoluted (breaking down of smaller particles).

Tablets are not 100% drug. What is the term for the fillers

Define Rate Limiting
The time it takes the drug to disintegrate and dissolve to be able to be absorbed.

Discuss pH absorption and those affected by pH.
Lower pH (1 or2) absorbs faater than alkaline fluids. The very young and elderly have lower pH levels, thus longer absorption time.

Discuss Enteric-Coated tablets.
These tablets do not disintegrate and dissolve till they reach the alkaline environment of the s.intestine. they may have a delayed response time. They should never be crushed.

Define Pharmacokinetic phase.
The process of drug movement to achieve drug action

What are the four processes of the pharmacokinetic phase?
1. Absoprtion
2. Distribution
3. Metabolism
4. Excretion

Area that most oral drugs are abosrbed is….
….the small intestine

What causes the small intestine to be a site of high absorption for oral drugs?
Mucosal Villi

What are three causes of reduced absorption in the small intestine.
1. Disease
2. Drug effect
3. Removal of s.intestine

What happens to protein-based drugs in the s.intestine.
Destroyed by digestive enzymes

What are three ways drug particles are moved to from the GI tact to body fluids.
1. Passive absorption (w/gradient)
2. Active absorption (against gradient)
3. Pinocytosis (engulfed by cell)

Discuss the Characterisitics of absorption
Drugs that are lipid soluable pass through the GI membrane readily. Water-slouable dugs need a carrier (enzyme or protein). Large particles pass through if they are nonionized. Calcium bicarbonate and antifungals need acid and thus should be taken with food. Hydrochloric acid destroys some drugs, these must be given in higher dosages

7 factors effecting absoprtion
1. Blood flow
2. Pain
3. Stress
4. Hunger
5. Fasting
6. Food
7. pH

Where do IM drugs abosrb the fastest?
Highly Vascular areas (i.e. deltoids)

What is first pass effect?
When the drug passes to the liver. Warfarin and morhpine. This decreases the drugs bioavailibility

Define bioavailability
Percentage of drug that enters systemic circulation

Oral vs IV bioavailibility
Oral route drugs that pass through the hepatic system are also absorbed by less than 100%. IV is uaually abosrbed 100%

How much more potent should oral drugs be than IV drugs related to bioavailibility
3-5 times

5 factors affecting bioavailability
1. Drug form
2. Route
3. GI mucosa and motility
4. Food and other drugs
5. Changes in liver function or inadequate hepatic blood flow

Liver dysfunction’s affect on bioavailability
Increase the effect of the drug because the liver has a decreased ability to metabolize the drug

How does liver dusfunction affect a patient?
It causes greater concenctrations of the drug and may lead to toxicity or overdose

Define distribution
process by which the drug becomes available to body fluids and body tissues

Distribution is affected by which three factors
1. Blood flow
2. Drugs afinity to tissue
3. Protein-binding affect

Discuss volume of drug distribution (Vd)
It is a factor that is dependent on drug dose and its concentration in the body

Define protein-binding affect
When a drug becomes bound to a protein, typically albumin. Percent of the drug that is bound is inactive, the percent of the drug that is free is active. As free drug is used up, protein-bound drug is released.

Four categories of protein-binding drugs?
1. Highly protien-bound-100%-89%
2. Moderately Highly Protein-bound-89%-61%
3. Moderately protein-bound- 60%-30%
4. Low protein-bound 30%-0%

Complications with the protein-binding effect
1. Two highly protein-bound drugs given concurrently compete for sites, leaving extra free drug in body, may lead to toxicity
2. Low protein levels (malnutrition, old age) leaves less sties to bind to, may lead to toxicity.
3. Low serum protein level leads to the free drug going to nonspecific tissues until needed, leaving no free drug in circulation. Seen in liver & kidney disease, older adults with hypoalbuminemia (leaving to few binding sites)

Three things a nurse should check for
1. Protein-bind percentage of Rx
2. pt’s albumin level
3. Plama protein level

Define metabolism (Biotransformation)
drugs that are metabolized in GI tract and liver, liver is primary

What are the actions of the liver?
Drugs are either activated or inactivated. Activation means the the drug particles are converted to active metabolites increasing the pharmacologic respnse. Inactivation uses liver enzymes to to convert the drug particles to inactive metabolites which are then excreted. a large % of drugs are lipible soluable and are converted to water soluable substance for excretion.

How does liver disease affect metabolism?
Disease such as cirrhosis and hepatitis alter the livers enzymes. a decreased metabolism can lead to accumulation and toxicity.

Define Half-life
Time it takes for one half of the drug concentration to be eliminated

Discuss the half life theory
650mg of aspirin with a half life of 3 hours. After 3 hours there will be 325mg…after 6 hours there will be 162….after 9hrs 81mg…after 12hrs 40mg…15 hrs 20mg..18hrs 10mg.

How long is a short half life? Long half life?
Short= 4-8 hrs. Long= more than 24 hours.

Define excretion
How the drug is removed from the body

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