How Drugs Work p1 Flashcards
Pharmacodynamics is the study of…
How drugs interact with the body to produce effect
- AKA: How the drugs affect the body
How do drugs work? They work in a variety of ways: (3)
- Drugs alter existing cellular functions.
- Hormones effect DNA expression. - Drugs alter the chemical composition of body fluids.
- Chelators bind ions as lead. - Drugs can form a chemical bond with receptors on target cells within the animals body.
Agonist receptors vs Antagonist receptors
- Agonist:
Drug that binds to a cell receptor & causes action. - Antagonist:
Drug that inhibits or blocks the response of a cell when the drug is bound to the receptors (antidote).
Pharmacokinetics is the…
Physiological movement of drugs into, within, & out of the body
- AKA: How the body affects the drug
What are the four steps of pharmacokinetics?
Hint: Think of the def of pharmacokinetics
- Absorption
- Distribution
- Biotransformation (metabolism)
- Excretion
Drug absorption is the ____ of drug from the site of ___ into the fluids of the body that will carry it to its ___ of action.
Drug factors include drug ___, ___, & ___ size.
Patient factors include the animals ___ and ___ status.
- Movement
- Administration
- Site(s)
- Solubility
- pH
- Molecular size
- Age
- Health status
Bioavailability is the percent…
Of drug administered that actually enters the systemic circulation.
- Drug form is important; oral drugs must have different properties than parental drugs.
Therapeutic range is drug concentration…
Amount in the body that achieves desired treatment affect.
- To maintain therapeutic concentration in the body, a drug must be given at the same rate as it is eliminated.
Subtherapeutic is a drug given…
In an amount below the goal for treatment effect
T/F: Subtherapeutic technique can be used with some antibiotics
False! This should be avoided as 1. It can create antibiotic resistance and 2. Failure of dose may be incorrectly interpreted as failure of the drug.
Therapeutic Administration
Define each for therapeutic administration:
1. Dose
2. Dosage interval
3. Route of administration
- Amount of drug given at one time.
- Record as units of mass (mg, g, gr).
- Not recorded in mL or tablets. - How often drug is given; Time between administrations of separate drug doses.
- Means by which a drug is given (IV, PO, SQ, etc).
T/F: The dose of the drug should be written as tablets or mL on the patient record and drug label for clients.
False! Dose should be written in units of mass, such as: mg, grams, &/or grains. It should not be recorded as tablets or mL on the patient record.
ALTHOUGH! On drug labels to clients, you may write tablets or mL IF concentration is clearly indicated.
Loading dose vs Maintenance dose
- Loading dose
- Initial dose that is larger than maintenance dose.
- Purpose is to rapidly raise serum concentration of drug to therapeutic range (not always necessary). - Maintenance dose
- Dose given to maintain drug at therapeutic levels in serum.
Name each abbreviation
1. SID
2. BID
3. TID
4. QID
5. PRN
- Once daily = qd
- Twice daily = q12h
- Three times daily = q8h
- Four times daily = q6h
- As needed
Parenteral is…
A drug given by injection
- IM
- IV
- SQ
Define each
1. Bolus
2. Constant-rate infusion
- Drug administered IV at one time (seconds to hours).
- Drug placed into intravenous fluids and given continuously.
Extra-vascular injection (extravasation) is an…
Injection of a drug outside of the vein that was intended to be into the vein.
- Sometimes these are uncomfortable to the Pt & interrupt intended therapy but will not damage tissues (ex: LRS).
- Some drugs (ex: chemo agents) will cause dramatic tissue damage if extravasation occurs!
Intraarterial injections (IA) are ___ due to drug being delivered to the nearest tissue & drug not mixing into ___ of general circulation.
It is difficult to give IA injections, you may see bright red ___ stream into syringe when you pull back (or self-fill). Sometimes a “___” of pulse is felt in needle tip.
- Avoided
- Blood
- Blood
- “Bounce”
Define each administration route:
1. Intradermal (ID)
2. Intraperitoneal (IP)
3. Transdermal (TDS)
4. Aerosol
*IV, IM, SQ, PO not included bc u know them already
- Within the skin (rarely used for Tx)
- Used for tuberculosis (TB) testing. - Within the abdominal cavity
- Used in neonates & wildlife medicine. - Across the skin
- Patches or ointments applied to the skin in which the med has the ability to pass through the skin & into the body.
- Effective dosing only occurs with a limited number of drugs. - Inhaled therapy
What are the four basic mechanisms of pharmacokinetics when moving across a cell membrane?
- Passive diffusion
- Facilitated diffusion
- Active transport
- Pinocytosis/phagocytosis
Passive diffusion is movement of particles from an area of ___ concentration to an area of ___ concentration. This is good for ___ lipophilic, nonionic particles.
Facilitated diffusion is ___ diffusion that uses ___ carrier molecule. This is good for ___ molecules that aren’t ___ soluble.
- High
- Low
- Small
- Passive
- Special
- Bigger
- Lipid
Active transport is when molecules move ___ the concentration gradient from areas of ___ concentration of molecules to areas of ___ concentration of molecules. This involves both a carrier ___ and ___!
- Against
- Low
- High
- Molecule
- Energy
T/F: Active transport is good for accumulation of drugs within a cell
True
Pinocytosis/phagocytosis molecules are physically ___ in or ___.
Pinocytosis is regarding ___ while phagocytosis is regarding ___ particles.
This is good for ___ molecules or liquids, but ___ used.
- Taken
- Engulfed
- Liquids
- Solid
- Bigger
- Rarely
Carrier mediated transport is the rate of transport…
Limited by the number of available carrier molecules
- Affects facilitated diffusion & active transport
What is the bioavailability of…
1. IV drugs
2. Topical drugs
3. Oral & SQ drugs
- 100%
- 0%
- Variable based on factors:
- pH
- Lipophilic character
- Molecule size
- GI motility
First-pass effect is a drug…
That is almost completely removed by the liver prior to reaching the circulation. (This is why some drugs are IV only & not PO)
- How/Why? All blood leaving the small intestines first pass thru the liver to have toxins removed prior to joining the general blood circulation.
For tablets, granules, & powders, they must ___ completely before leaving the small intestine. This means the molecule size must be ___ enough to pass through the mucous membrane of the small intestine.
Liquid drugs ___ need to dissolve!
- Dissolve
- Small
- Don’t
Sustained-release medications generally are ____ in small animal medicine because they are unable to ___ fast enough to reach ___ blood levels.
- Ineffective
- Dissolve
- Therapeutic
