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The most important properties of an ideal drug are:
Effectiveness, safety and selectivity
Is there such thing as a safe drug?
no, all drugs can cause harm
Is there such thing as a selective drug?
No, all drugs can cause side effects
Object of drug therapy:
to provide maximum benefit with minimum harm.
The goal of pre-administration assessment is to gather data needed for:
- 1. Evaluation for therapeutic and adverse effects
- 2. Identification of high risk patients
- 3. assessment of the patient's capacity for self care
Analysis and diagnosis phase of treatment:
- Judging the appropriateness of prescribed therapy
- identifying potential health problems treatment might cause
- characterizing the patient's capacity for self care
Planning is directed at:
- defining goals
- establishing priorities
- establishing criteria for evaluating success
What was the Food, Drug and Cosmetic Act of 1938?
The first legislation to regulate drug safety
What did the Harris-Kefauver Amendement in 1962 do?
First legislation to demand that drugs actually be of some benefit.
The Controlled Substances Act
Passed in 1970, set rules for the manufacture and distribution of drugs considered to have potential abuse.
FDA Ammendments Act
passed in 2007, expanded the mission of the FDA to include rigorous oversight of the drug safety after a drug has been released for marketing.
The most reliable way to objectively assess drug therapy.
When working with a new drug, should you look for adverse effects?
yes, some adverse effects may not yet been detected. When working with a new drug you should be especially watchful for previous unreported adverse events.
Drugs have three types of names:
- 1. chemical name
- 2. generic or nonproprietary name
- 3. trade or propretiary name
Pharmacokinetics has four basic processes:
- 1. Absorption
- 2. Distribution
- 3. Metabolism
- 4. Excretion
What do pharmakokinetic processes determine?
It determines the concentration of a drug at its sites of action, and determines the intensity and time course of responses.
To move around the body, drugs must cross membranes either by:
- 1. Passing through pores
- 2. undergoing transport
- 3. penetrating the membrane directly (Most common)
Important because it can transport a wide variety of drugs OUT of cells. Found in the liver, kidney, placenta, intestine, brain capillaries.
How do drugs cross membranes?
To cross membranes, a drug must penetrate the lipid bilayer of the membrane. Lipid soluble drugs can cross easily while polar or ionized drugs cannot.
How to acidic drugs ionize?
In basic (alkaline media)
How to basic drugs ionize?
In acidic media
How is drug absorption enhanced?
- Rapid drug dissolution
- High lipid solubility
- large surface area for absorption
- high blood flow at site of administration
Advantages of intravenous administration:
rapid onset, precise control over the amount of drug entering the blood, suitability for use with large volumes of fluid, suitability for irritant drugs
Disadvantages of intravenous admininstration
high cost, difficulty; inconvenience; danger because of irreversibility; and the potential for fluid overload, infection and embolism.
Oral administration has the advantages of:
ease, convenience, economy and safety.
The principal disadvantages of oral administration are:
high variability and possible inactivation by stomach acid, digestive enzymes, and liver enzymes (because oral drugs must pass through the liver before reaching the general circulation.)
where do Enteric-coated oral formulations release their contents?
Into the small intestine--- not the stomach.
The movement of drugs through the body.
The term blood-brain barrier:
refers to the presence of tight junctions between the cells that compose capillary walls in the CNS. Because of this barrier, drugs must pass through the cells of the capillary wall (rather than between them) in order to reach the CNS.
Many drugs bind reversibly to:
plasma albumin. While bound to albumin, drug molecules cannot leave the vascular system.
Drug metabolism is defined as:
the enzymatic alteration of drug structure.
Most drug metabolism takes place in:
the liver and is catalyzed by cytochrome p450 system of enzymes.
The most important consequence of drug metabolism:
is the promotion of renal drug excretion (by converting lipid soluble drugs into more polar forms)
Other consequences of drug metabolism are:
conversion of drugs to less active forms, conversion of drugs to more active forms, conversion of prodrugs to their active forms and conversion of drugs to more toxic or less toxic forms.
Some drugs can induce synthesis of hepatic drug metabolizing enzymes, what will occur?
They will accelerate their own metabolism and the metabolism of others drugs.
The term first pass effect refers to:
the rapid inactivation of some oral drugs as they pass through the liver after being absorbed.
Renal drug excretion has three steps:
- glomerular filtration
- passive tubular reabsorption
- active tubular secretion.
Drugs that are highly lipid soluble undergo:
extensive passive reabsorption back into the blood, and therefore cannot be excreted by the kidney (until they are converted to more polar forms by the liver.)
Drugs can be excreted into breast milk, why does this pose a problem?
Because it can pose a threat to the nursing infant.
For most drugs, there is a direct correlation between:
the level of drug in plasma and the intensity of therapeutic and toxic effects.
The minimum effective concentration (MEC) is defined as:
the plasma drug level below which therapeutic effects will not occur.
Therapeutic range, what is the difference between drugs with a wide therapeutic range and a narrow therapeutic range?
Drugs with a wide therapeutic range are relatively easy to use safely, whereas drugs with a narrow therapeutic range are difficult to use safely.
The half life of a drug is defined as:
the time required for the amount of drug in the body to decline by 50%.
When drugs are administered repeatedly, what will happen to their levels?
their levels will gradually rise and then reach a steady plateau.
The time required to reach plateau is:
- 1. Equivalent to about four half lives.
- 2. Independent of dosage size, although the height of the plateau will be higher with larger doses.
If plasma drug levels fluctuate to much between doses, the fluctuations could be reduced by:
- 1. giving smaller doses at shorter intervals (total daily dose is the same)
- 2. using continuous infusion
- 3. using a depot preparation