Pharm chapter 2 Flashcards
What is the study of the interactions between the chemical components of living systems and the foreign chemicals, including drugs, that enter living organisms; the way a drug affects a body?
pharmacodynamics
What are the four ways drugs work within the body?
- replace or act as a substitute for missing chemicals
- to increase or stimulate certain cellular activities
- to depress or slow cellular activities
- to interfere with the functioning for foreign cells
What involves the study of absorption, distribution, metabolism, and excretion of drugs?
pharmacokinetics
What is the clinical practice considerations of pharmacokinetics?
- the onset of drug action
- drug half-life
- timing of the peak effect
- duration of drug effects
- metabolism of the drug
- site of excretion
The amount of a drug that is needed to cause a therapeutic effect is called?
critical concentration
The actual concentration that a drug reaches in the body results from a DYNAMIC EQUILIBRIUM involving several processes which are?
- absorption from the site of entry
- distribution to the active site
- Metabolism in the liver
- Excretion from the body
The processes 0f dynamic equilibrium are key elements in?
- determining the amount of drug dose
- the frequency of dose repetition
What is the absorption of the oral route?
- the acidic environment of the stomach is the first barrier to the foreign chemical (the drug)
- the acid breaks down many compounds and inactivates others.
- the binders that are used often are designed to break down in a certain acidity and release the active drug to be absorbed.
What is the absorption of the IV route?
- reach there full strength at the time of injection, avoiding the initial breakdown.
- immediate onset, fully absorbed at administration because they are directly entered through the blood stream.
What is the absorption of the IM route?
- absorbed directly into the capillaries in the muscle and sent into circulation.
- takes time because the drug must be picked up by the capillary and taken into the veins.
What is the absorption of the subcutaneous injections route?
- deposits the drug just under the skin, where it is slowly absorbed into circulation.
- timing of absorption varies, depending on the fat content of the injection site and state of local circulation.
Factors that affect absorption of IV drugs are?
Nothing
Factors that affect absorption of intramuscular (IM) drugs are?
- perfusion of blood flow to the muscle.
- fat content of the muscle
- temperature of the muscle: cold causes vasoconstriction and decreases absorption; heat causes vasodilation and increases absorption.
Factors that affect absorption of subcutaneous drugs are?
- perfusion of blood flow to the tissue.
- fat content of the tissue
- temperature of the tissue: cold causes vasoconstriction and decreases absorption; heat causes vasodilation and increases absorption.
Factors that affect absorption of PO (oral) drugs are?
- acidity of stomach
- length of time in stomach
- blood flow to gastrointestinal tract
- presence of interacting foods or drugs
Factors that affect absorption of PR (rectal) drugs are?
- perfusion or blood flow to the rectum
- lesions in the rectum
- length of time retained for absorption
Factors that affect absorption of mucous membrane drugs are?
- perfusion or blood flow to the area
- integrity of the mucous membranes
- presence of food or smoking
- length of time retained in area
Factors that affect absorption of topical (skin) drugs are?
- perfusion of blood flow to the area
- integrity of skin
Factors that affect absorption if inhalation of drugs are?
- perfusion or blood flow to the area
- integrity of lung lining
- ability to administer drug properly
What involves the movement of a drug to the body’s tissues?
distribution
What are the factors that can affect distribution?
- drug’s livid solubility and ionization and the perfusion of the reactive tissue.
What is the biotransformation (metabolism) that drugs undergo once in the body?
- the liver is the single most important site for biotransformation (metabolism)
- breaks down medications
- helps prevent medications from causing adverse effects on the body.
- first pass effect: drugs that are taken orally are absorbed from the small intestines directly into the portal system before going into distribution.
Drugs that are taken orally are absorbed from the small intestines directly into the portal system before going into distribution. This is called?
first pass effect
The removal of the drug from the body is called?
excretion
What is the main site of excretion?
the kidneys
What are all the sites
of drug excretion?
skin, lungs, bile, saliva, feces, kidneys
Factors that influence the actual effectiveness of drugs in the body are?
weight, age, gender, physiological factors, pathological factors, genetic factors, immunological factors, psychological factors, environmental factors, drug tolerance, cumulative effect
Drug weight factor:
- people who are much heavier may require larger doses to get a therapeutic effect from a drug because they have increased tissues to perfuse and increased receptor sites in some reactive tissue.
- lighter people may require smaller doses of a s drug. toxic effects may occur at the recommended dose if the person is very small.
Drug age factor:
- children metabolize many drugs differently than adults do, and they have immature systems for handling drugs.
- older adults undergo many physical changes that are a part of the aging process. They are more likely to be taking multiple drugs for various conditions. Their bodies may respond very differently in all aspects of pharmacokinetics—less effective absorption, less efficient distribution because of fewer plasma proteins and less efficient perfusion, altered biotransformation or metabolism of drugs because of age-related liver changes, and less effective excretion owing to less efficient kidneys.
Drug gender factor:
- Physiological differences between men and women can influence a drug’s effect.
- When giving IM injections, men have more vascular muscles, so the effects of the drug will be seen sooner in men than in women.
- Women have more fat cells than men do, so drugs that deposit in fat may be slowly released and cause effects for a prolonged period
- Women should be questioned about pregnancy always
Drug physiological factors:
- difference such are diurnal rhythm of the nervous and endocrine systems, acid base balance, hydration, and electrolyte balance can affect the way a drug works
Drug pathological factors:
- the disease that the drug is intended to treat can change the functioning of the chemical reactions within the body and thus change the response to the drug.
- Gi disorders can affect absorption of oral drugs
- vascular diseases and low blood pressure can alter the distribution of a drug, preventing it from being delivered to the reactive tissue.
- liver and kidney diseases affect the way that a drug is metabolized and excreted which can lead to toxic reactions.
Drug genetic factors:
- Some people lack certain enzyme systems necessary for metabolizing a drug, whereas others have overactive enzyme systems that cause drugs to be broken down more quickly.
- others have differing metabolisms or slightly different enzymatic makeups that alter their chemical reactions and the effects of a given drug
Drug immunological factors:
- development of allergies to a drug
- development of antibodies to a drug
Drug psychological factors:
- patient’s attitude about a drug has been shown to effect how that drug works.
- patient following the regimen correctly
Drug environmental factors:
- some drugs effects are enhanced by a quiet, cool, non-stimulating environment. (relaxing medications)
- others by temperature (antihypertensives)
Drug tolerance factors:
- the body can develop a tolerance over time.
Drug cumulation factors:
If a drug is taken in successive doses at intervals that are shorter than recommended, or if the body is unable to eliminate a drug properly, the drug can accumulate in the body, leading to toxic levels and adverse effects.
