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Pharmacokinetics and Pharmacodynamics
Terms in this set (102)
Medicine + Movement
How drugs pass through the body
Concentration of a drug in the body depends on 4 things
How the drug moves from site of administration across a membrane into the blood
Once in the blood, how the drug is distributed throughout the body
How the drug is altered/changed in the body
How the drug is removed from the body
Absorption is problematic due to its...
Primary method of moving drugs across membranes is
Absorption is affected by
- Concentration of drug (each drug has its own PH)
- Chemical properties of drug
- Bioavailability of drug
- Fillers, Route, GI tract
- Chemical Properties of environment : PH of body, Blood, Urine, lipid soluble or insoluble etc.
To readily cross membranes, a drug must be....
LIPID soluble (lipophilic)
Why are LIPID-SOLUBLE drugs more easily absorbed?
How do LIPID-
SOLUBLE drugs absorb?
soluble drugs can dissolve directly into the
portion of the membrane of a cell and diffuse into that cell.
-Lipid INsoluble drugs require a water filled PORE, CHANNEL or PORTAL which they can pass through.
onized drugs are lipid ______________
The amount of the drug that reaches the CIRCULATION
Diffusion of a drug across a membrane depends on 4 MAJOR CIRCUMSTANCES:
- SURFACE AREA of the guts (with all the lumen)
- THICKNESS of the guts (membrane)
- DWELL TIME of the guts (peristalsis, how full, transit of bowels)
- BLOOD FLOW to the guts
Diffusion of a drug across a membrane depends on 4 MINOR methods
- AQUEOUS CHANNELS (holes/ports in cellular membrane)
- ACTIVE TRANSPORT (Kidney specific, certain drugs)
- FACILITATED DIFFUSION (PgP)
(hydro- or lipo-philic)
Acidic drugs are usually absorbed in the
Alkali drugs are generally absorbed in the
P-Glycoprotein (PgP) aka "Efflux Protein" or "Multi-Drug Transporter Protein" is what?
Special protein that MOVES DRUGS BACK ACROSS MEMBRANES (
) to try and excrete it as a foreign body, via GI, Urine etc
P-Glycoprotein (PgP) is found where?
Most important minor method of diffusion across membranes
DRUG SOLUBILITY (is it hydro or lipo philic/ water or fat soluble)
What is the BIOAVAILABILITY SCALE (aka
The higher the number =
a generic drug will be
Most absorption occurs in
emptying means __________absorption
(takes LONGER for drug to enter Small Intestine)
emptying means _________absorption
(drug enters Small Intestine QUICKER)
emptying means ___________absorption
(Longer DWELL TIME allows more more diffusion)
The amount of a drug that actually reaches the circulation is referred to as a drug's ___________________
emptying means ______________absorption
(Less DWELL TIME = less chance for diffusion)
Characteristics of Sublingual/Buccal drugs
(where is it used heavily?)
- Diffuses DIRECTLY to circulation
- Good alternative to injections in home settings
( used HEAVILY in HOSPICE)
Characteristics of Rectal drugs
- May have
- Rectum is VASCULAR, baby
- Butt Absorption is ERRATIC & UNPREDICTABLE
- Psychologically, people
stuff going in their butt
Characteristics of SubCutaneous (SQ/SC) drugs
- Faster than ORAL
- Still RELATIVELY SLOW absorption
- FAT tissue is a RESERVOIR for the drug
- Can't use IRRITATING drugs SQ
Circulation to tissue
Amount of Ionization
amount of adipose tissue
Absorption rate of SQ drug can be slowed how?
By adding a vehicle.... (ex: insulin + zinc)
Characteristics of IntraMuscular (IM) drugs
faster than SQ (IM vs SQ = controversial)
Circulation to tissue
Amount of Ionization
Absorption rate of IM drug can be slowed how?
By adding a vehicle.... (ex: PCN + Procaine)
Characteristics of IntraVenous (IV) drugs
- Potential for IMMEDIATE ACTION TO
rate of administration
rate of action
- Cardiac OUTPUT affects distribution
- MISTAKES f@cking suck and can't be taken back, yo!
[Risk of INTRODUCING PATHOGENS systemically]
Characteristics of Epidural ("above/upon/around" + "dura mater") drugs
than paralyzing someone]
- Injection into area outside Dura Mater
- Less medication needed
[risk of INTRODUCING PATHOGENS into CNS!]
Characteristics of IntraThecal ("within" + "spinal theca") drugs
- go directly INTO spinal subarachnoid space
BYPASSES BLOOD BRAIN BARRIER!!!!!
- Less medication, longer effect
[risk of INTRODUCING PATHOGENS into CNS!]
Characteristics of Pulmonary drugs
- LOCAL effects: occur along Bronchial passages
- SYSTEMIC effects: drug must reach deeply into ALVEOLI
- Volatile liquids/gases (ex: general anesthesia) RAPIDLY absorbed in mucosa of Respiratory tract
Characteristics of Topical drugs
- SYSTEMIC absorption if LIPID SOLUBLE drugs (can pass through cells of epidermis)
- LOCAL absorption if LIPID INSOLUBLE drugs (can't easily pass through cell lipid bilayers...
pass through glands)
- Blood supply
What are TOPICAL drugs not appropriate for (3 things)?
- PRNs (not fast enough)
- as a "Breakthrough" medication (not fast enough)
not appropriate for INFANTS:
Body surface area to weight ratio
don't kill babies!
Characteristics of Optic and Ear Drugs?
- LOCAL action only, NOT systemic actions
Characteristics of Nasal drugs?
- MAINLY LOCAL.... a very
Cytochrome P450 ("CYP") Enzymes
- MAJOR drug metabolizing ENZYME
- Responsible for ~80% of OXIDATIVE drug Metabolism
- Can metabolize ~90% of Drugs we use today
- GI tract
"Drug to Drug" Interactions can __________ Absorption of one or both of the drugs
DECREASE or DELAY absorption
"Food to Drug" Interactions can __________ Absorption of the drug
DECREASE or DELAY absorption
(Fatty foods can LOWER GI motility, DELAYING absorption)
Movement of a drug from BLOOD --> TISSUES --> TARGET SITE
on _______________ status of Pt.
- Cardiac output?
- Cold temperatures...shunting of bloodflow?
Rate of DISTRIBUTION of a drug depends on
-BLOOD FLOW to and from tissues
-BINDING CAPACITY to specific tissues
-PLASMA PROTEIN BINDING CAPACITY
to Distribution (placenta, Blood-Brain)
Explain TISSUE BINDING CAPACITY...
- Some drugs prefer to bind to SPECIFIC tissues, may bind to these tissues in LARGE amounts. This is
! As BLOOD concentration of drug DECREASES, tissues will RELEASE the drug.
- FAT tissue tends to store LIPID SOLUBLE, and its RELUCTANT to RELEASE the drug, as Blood supply to FAT is LOW =
If a drug BINDS to tissues, the ONSET of the drug is __________.
The LEVELS of the drug in the body remain fairly ____________, and the ACTION of the drug is ____________________
A BOUND drug is ___________________ to activate a receptor
BOUND drug is _____________________ to activate a receptor
Drugs like to ________ to sites on PROTEINS. ALBUMIN is most influential in this process
FREE DRUG + PLASMA PROTEIN (albumen) =
Only a/n ______________ drug can reach its target cell
The less ALBUMEN in one's blood stream, the _______________ Free Drug reaches target cells = the __________________ Drug RESPONSE
SOme drugs (like coumadin/"warfarin") have
99% binding capacity
, so dosage must be calculated to ensure that the
remaining 1% of unbound drug
is enough to be ________________
Explain the Drug-Protein Complex
When a free drug BINDS with a plasma protein like Albumen, it becomes bound to that protein and thus forms a DRUG-PROTEIN COMPLEX
If drug "A" is reversible and bound to proteins, and you add a drug "B" (which has a HIGHER affinity for protein binding than "A"), what can occur?
COMPETITION FOR BINDING SITES!
Drug "B" can BUMP drug "A" off the limited number of protein binding sites and take its place. This suddenly INCREASES the amount of free drug "A" in the bloodstream, and INCREASES drug "A's" effect on target sites
Ratio of "Free" to "Bound" drug in the body will _____________ for every individual drug
- Drug XXXX and YYYY are both equally bound to albumen, saturating all the albumen.
- More of drug YYYY is taken, it can't bind to the saturated Albumen, so it binds to its target receptor sites and has its effect.
- You STOP taking drug XXXX, the XXXX that is already bound to the albumen gradually deteriorates, reopeneing available binding sites.
- Those newly available binding sites ATTRACT the target receptor bound drug YYYY to leave their target site and attach to the ALBUMEN.
what does this mean for the effect of drug YYYY?
Drug YYYY which WAS bound to it starget receptor site, got pulled back into the bloodstream to bind with the newly oipened ALBUMEN receptor sites.
Drug YYYY stops working after XXXX was discontinued.
stopping or starting a drug that binds to free proteins, can change the free drug levels of...?
OTHER protein bound drugs!!!
Blood Brain Barrier does what to 90% of drugs?
Brain capillaries are less permeable than other capillaries.
BBB Doesn't allow HYDROPHILIC drugs to pass from Blood to Brain
Placental Enzymes INACTIVATE drugs as they cross from Maternal to Fetal circulation
Placental Barrier is less effective than Blood Brain Barrier, it often lets what types of drugs through? ("SANA" gonna get your baby!)
BIO-TRANSFORMATION is also known as
The CONVERSION of a DRUG to a more WATER SOLUBLE (IONIZED) compound ("metabolite") that can be REMOVED from the body easily.
Main site of METABOLISM?
(mainly hepatic enzymes:
Other sites of drug METABOLISM (other than liver...hint: all the f#ck over!)
HEPATIC ENZYMES can perform
- INACTIVATE a drug
- ACTIVE an inactive drug
- Make drug MORE WATER SOLUBLE
- Convert a
Proper metabolism requires....
A HEALTHY HEPATIC SYSTEM!
The body sees a drug as __________________, and tries to _________________
as a FOREIGN OBJECT
tries to GET RID OF IT (usually via liver).
BIG question to ask when it comes to METABOLISM?
What is the _______________ status? What is the ______________ ___________ to the Liver?
What is the
What is the
to the liver?
Define "FIRST PASS EFFECT"
drugs move from stomach --> Small Intestine --> Liver
-Drug Concentration is greatly decreased
- What drug is left after liver metabolization is
released back into general circulation
THIS CAN OCCUR MORE THAN ONE TIME --> 2nd pass, 3rd pass etc.
Drugs that utilize
metabolism to convert from inactive to an active form via first pass are called:
ORAL drugs are subject to first pass (SL, Buccal, SQ, IM, IV are not).
Which other route is partially/minimally subjected to first pass?
Why is a PO morphine dose much higher than an IV morphine dose?
FIRST PASS will neutralize a % of the Oral drug, whereas IV directly enters circulation and is not subjected to a first pass
are the only three ___________________ agonists
are ________________ agonists
CYP1, CYP2, CYP3 are important enzymes in the
Cytochrome P450 SYSTEM
of p450 system results in ____________________ metabolism of a drug
4 stated examples of
known, common p450 INHIBITORS
Type of Antidepressant
Type of juice
Type of antacid
Type of Chalk blockers
- GRAPEFRUIT JUICE
- CIMETIDINE (tagamet)
- Calcium Channel Blockers
have the ability to ____________ metabolic activity in the liver
________________ have underdeveloped P450 systems, making Liver metabolism UNPREDICTABLE
_________________ have questionable responsiveness to Liver loads, often due to large amounts of drugs being taken (polypharmacy)
Examples of p450 Enzyme
(will reduce therapeutic levels of drug involved)
Charcoal broiled meats
(similar to smoking)
(increases amount fo enzymes synthesized in liver --> increases rate of metabolism)
If Liver function tests in someones diagnostic lab tests are elevated....we know that metabolism will be
(more or less? don't know...
of a drug from the body
Primary site of EXTRETION
of excretion determines the _____________________ of a drug in the bloodstream..
- FREE, UNBOUND,
DRUGS will pass _______________ through the Golmerulus.
Clearance = How
can the body
PROTEIN/LIPID BOUND drugs...will they pass so easily? (Think Glomerulus and large albumen proteins)
NOPE. Protein Bound drugs cannot be excreted!
Probably go via GI/Feces
What 2 Labs do we want to have "within normal limits" in order to have efficient excretion?
(In order for those 2 labs to be WNL, the body needs to have three things...)
CREATININE & BUN
(Body needs to have:)
- Good CARDIAC OUTPUT
Lipid soluble drugs that can't pass via glomerulus filtration, are reabsorbed from renal tubules and enter back into the _______________________
_____________________ of Urine can help determine excretion vs reabsorption of a drug in Kidneys.
PH of urine can be altered to slow reabsorption of a drug in ____________________ Situatiaions
IF overdose with an acidic drug(Aspirin/ASA), then we would want to ____________________ the urine with NaHCO3 (Sodium Bicarbonate)
If overdose with an alkaline drug, we would want to _______________ urine with VIT C or Ammonium Chloride
Just like some drugs *compete* for receptor sites, drugs can also
for __________________ by renal enzymes. THus we can give drug A to slow ___________________ of drug B and keep drug B in the blood circulation lo
some drugs *compete* for receptor sites, drugs can also *compete* for __________________ by renal enzymes. THus we can give drug A to slow ___________________ of drug B and keep drug B in the blood circulation longer...or the other way around....(think of aspirin and sodium bicarbonate)
Other than the kidneys, "Clearance" can occur elsewhere in the body, such as:
- Mammary Glands (via
- Sweat, Saliva
Describe the Enterohepatic cycle
LIPIDS are broken down via BILE SALTS excreted by the LIVER into the INTESTINE.
The BILE SALTS enter the BLOOD CIRCULATION then return back into the LIVER.
What is the net effect of the enterohepatic cycle in comparison to Renal excretion?
- Enterohepatic cycle takes LONGER to excrete a drug caught up in its cycle.
PROLONGED drug action compared to a drug that si quickly excreted via the kidneys
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