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
Which drugs interact with dietary tyramine (wine, processed meats?
What is the effect?
Isocarboxazid
Tranylcypromine
hypertensive crisis
Which drugs interact with milk?
What is the effect?
Tetracycline (sumycin)
reduced absorption = reduce therapeutic effect
which drugs interact with protein?
effect?
Levadopa (parkinson’s drug)
SUDDEN loss of therapeutic effect
Additive interactions
Combined effect of two similar drugs is equal to sum of each drug effect
1+1=2
Dangerous!
Synergistic effect
one drug effect is greater if you give it with another drug
Antagonistic effect
one drug is decreased or blocked if you give it with another drug
Drug-food interactions
food changes way drug affects the body
increased blood levels (enzyme inhibitor) or decreased blood levels of med (enzyme enhancer)
What is the Pregnancy and Lactation Labeling Rule?
mandates 3 sections for drug labelling:
pregnancy
lactation
reproduccutive potential
What should be considered with medications and breastfeeding?
- how much breastmilk the infant consumes
-size of infant
What happens if you administer a drug intramuscularly in a neonate (birth-1 month)
Absorption is delayed and erratic
Onset of action
time it takes for drug to have a therapeutic response
Peak effect
Time it takes for a drug to reach its full therapeutic effect
Duration of action
Length of time the therapeutic effect lasts
Trough drug level
point in time where the drug is at its lowest concentration in the blood
Peak drug level
Point in time where concentration of drug is highest
How do drugs enact a therapeutic effect?
Changes in cell function, changes in cell environment, and changes in enzyme action
Agonist
Medication that binds a receptor and causes a greater than typical response
Antagonist
Medication that binds a receptor and block a response or causes a less than typical response
Competitive antagonists
Antagonist med that competes with agonists
At high doses, it causes a decreased therapeutic effect by agonists
Noncompetitive antagonists
Completely block agonists from binding a receptor (at high enough doses)
Selective drug interaction
medication has specific receptors it binds to in order to enact the desired effect
very selective - binds fewer receptors
low selection = binds a lot of receptors = more side effects
Adverse drug reactions
Non-therapeutic and unintended response to a medication taken at a therapeutic dose
Precautions
Steps taken against factors that can cause ADRs with a certain medication
Extra precautions taken if the client has multiple conditions or chronic disease
Example of a precaution: limit food or change admin schedule if drugs interact
Contraindication
Conditions that can cause a serious adverse drug reaction and indicate the drug should not be prescribed
Tolerance
decreased therapeutic response to a drug
Increase the dose to counteract
Sensitivity
Drug accumulation in the blood, often due to changes in metabolism (liver damage or kidney damage)
Toxicity
Adverse effects due to a toxic dose of a medication or kidney damage.
General things that impact pharmacokinetics in old age?
- increased body fat and decreased water
- increased gastric pH
-reduced peristalsis
-declined liver and kidney functioning
-fewer plasma proteins
-reduced cardiac output, vascular disease
