Pharmacology Principles Flashcards
What is the definition of drugs?
Medications or other substances that have a physiological on the body
What is absorption?
The drug travels from the site of administration to the blood
What is distribution?
The medication is distributed throughout the body to the target cells
Drug bioavailability
Factors that affect whether drug is able to enter the cell and enact effect, including an affinity for drug-receptor sites and binding to plasma proteins
Pharmacodynamics
Physiological effect a drug has on the body (what is the drug’s mechanism of action?)
Pharmacogenetics
How people’s genes affect response to medication
Why may someone need several doses of an oral medication for it to enact effect?
The first pass effect: after making it to the intestines, liver enzymes will metabolize the drug rendering some inactive. Some will escape metabolism completely and enter the blood to become either plasma protein bound (inactive) or bound to the receptor site (active).
What route of admin does not undergo absorption?
Intravenous
Pros and cons of transdermal application
Pros: slow, steady stream of the drug directly to the blood without passing through liver.
good for a long period of time
more convenient than frequent injections or inhalation
Cons: Lipophilic and small molecules only
What are factors that affect drug absorption in neonates and pediatrics?
Acid-producing cells in stomach are immature until ages 1-2.
Gastric emptying may be decreased because of slow/irregular peristalsis.
Higher drug levels in blood due to immature liver
What affects oral medication absorption in the elderly?
Decreased blood flow to GI tract
Changes in gastric pH
Variations in plasma proteins
What affects subcutaneous, intramuscular, and transdermal medication absorption in the elderly?
Lower cardiac output and decreased peripheral circulation
Less body fat decreases absorption for transdermal
What causes drug side effects?
A drug primarily binds to its target receptors to enact or block an effect.
If it also binds to other unintended receptors, it can cause side effects.
Are most drugs bound to plasma proteins or free?
95-98% is bound to plasma proteins and can act as a reservoir that is slowly released over time
Why does a patient taking several highly protein-bound medications experience more side effects?
The drug that has the higher affinity for plasma proteins will bind first, which prevents the other drug from binding strongly to protein and the target site (some will but there will be a lot of active form in circulation without strong albumin binding)
Secondary medications float in circulation and are more likely to bind unintended receptors.
How do medications pass the blood-brain barrier?
They must be lipid soluble or have a “carrier” medication that can get through
Ex: Sinemet (Parkinson’s drug) is a combo of carbidopa (carrier) and levadopa (converted into dopamine)
What are considerations regarding medical distribution for neonates and pediatrics?
Decreased fat content due to greater total body water
Liver is still forming and protein binding capacity is decreased = more active drug in circulation
BBB is developing and allows more drugs to enter the brain
What are considerations for medication distribution in the elderly?
Decrease in total body water and muscle and increase in fat (longer duration of action for meds)
Albumin decreases = more active free drug in circulation (need lower dose!)
What is the first pass effect?
Orally administered drugs are broken down in the liver (converts a portion of the drug into a water-soluble waste form to be better excreted by the kidneys)
Why do we say the liver detoxifies?
The metabolites that are produced after enzymatic breakdown are less chemically active
What affects drug metabolism in neonates and pediatrics?
In babies and young children: developing liver produces fewer enzymes (less metabolism = more active drug in blood)
In older children: increased metabolism = higher doses needed
What affects drug metabolism in the elderly?
Significant decline in metabolism, including first-pass metabolism
Liver disease
Dosages should be adjusted according to liver function and anticipated metabolic rate
Why does grapefruit juice increase certain drug levels in the blood?
It affects the metabolic rate of SOME medications by lowering CYP3A4 (part of the CYP450 family of enzymes) in the intestines
Which drugs interact with grapefruit juice?
What is the effect of the interaction?
Sertraline
Allegra
Procardia
CYP450 enzymes are reduced by grapefruit metabolism - more drug will be active in circulation
