Lets gooooo Flashcards
(89 cards)
Whats the concentration time curve
describes the drugs concentration changes in the plasma with time
what happens in the alpha distribution phase (two compartment model)
drug concentration decreases rapidly (distribution half life (minutes))
what happens in the beta elimination phase
drug concentration decreases slowly (distribution half life (hours))
Three compartment model
aminoglycosides and phenicols, renal cortex and re-distribution. Terminal elimination can last days or weeks. Watch for WP!!!
Extravasal drug administration (one compartment model)
t1/2a
tmax
t1/2el
IM, SC, PO
t1/2a, Time until the drugs concentration doubles in the plasma
tmax clinical significance, time needed to reach Cmax
t1/2el time until 50% of the drug is eliminated
Apparent volume of distribution
20kg=1l Vd=0.05 Drug is distributed in blood plasma
20kg= 10l Vd=0.5 Drug is distributed in blood plasma and in Ec fluid space
20kg= 40l Vd=2 Drug is distributed in blood plasma =extracelluar space and intracelluar fluid space
any changes to the value of Vd may decrease efficacy or increase toxicity, if the dose is unchanged
whats a azalide and triamilide ?
Azithromycin and Triamcinolone !!!
Against Streptococcus suis
Florfenicol either IM or SC (not the best SC) (off label)
IM has fast onset
while SC has longer duration ?
Whats AUC
the Area under the curve reflects the actual body exposure to the drug after administration of a dose of the drug.
Whats F
Bioavailibility (F) is the fraction of a drug that reaches systemic circulation unchanged after administration, relative to the same drug given intravenously (IV)
drugs administered IV always have Bioavailibility of 1.
Clearance
Volume of plasma that is cleared of drug per time unit; ml/min or l/hour
Cl= Cl renal+Cl hepatic+Cl lung
Cl= D/AUC
Use of medicines in kidney failure
We use “A” option substances with a high therapeutic index:
we can modify the dose
or
the time interval between the repeated administrations
Without calculation and substances with high therapeutic index such as
AMOXICILLIN
Whats B option type of drugs
For the intermediate therapeutic index. Depends on time interval between two administrations. Also depends on Creatinine clearance (shows renal function).
B drugs (Warfarin, Digoxin)
increase time interval between administrations
*2
if CCr= 0.5-1ml/minute/kg
*3
if Ccr = 0,3-0,5ml/minute/kg
*4
if Ccr = if less than 0,3ml/minute/kg
whats Ccr?
Creatinine Clearance rate which also describes the renal function
Precise dosing regimen for modification for low therapeutic index = “C” option drugs.
When is it necessary?
What are the options?
How?
We do it for toxic drugs that are excreted by glomerular filtration such as aminoglycosides (gentamycin, neomycin, Amikacin,
What are the options? We modify the dose or do dosing interval modifications
How? Using the dose fraction (Kf)!
KF=ill Ccr/ normal Ccr
Modify the exact dosing regimen
Modified dose = normal dose*Kf
Modified dosing interval = normal interval/Kf
what you call the conditions when elevated levels of nitrogen and creatinine are in the blood
Azotemic
what do you call it when the urine and blood plasma have the same osmolarity
Isisthenuric
Drug examples in case of renal failure
Amikacin (c) bad
Amoxicillin (a) good
Cephalexin (b) good
Chloramphenicol N,A good
Digoxin (c) good
Gentamicin (c) bad
Nitrofurantoin (Cl) good
Oxitetracyclines (Cl) bad
Penicillin (a) good
Tobramycin (c) bad
Trimetoprim/ sulfamethoxazole (b/A) bad
Drug Examples in case of liver failure
Azatioprin (contraindicated)
Chloramphenicol (contraindicated)
Clindamycin (contraindicated)
Cyclophosphamide (Dosing interval)
Diazepam (contraindicated)
Doxorubicin (Dosing interval)
Doxycycline (Dosing interval)
Furosemide (Dosing interval)
Lidocaine (Dosing interval)
Metronidazole (Dosing interval)
Morphin (Dosing interval)
Oxitetracycline (contraindicated)
Phenobarbital (Dosing interval)
Teofillin (Dosing interval)
other conditions for which a modification of the dosing schedule is recommended
newborns or very young animals
old animals
The ratio of body fat to water spaces is also different in these cases, which affects the Vd of the substance
Whats LD
Loading dose is a diose given with one administration (or repeated a few time, quickly) with which the desired drug concentration can be reached immediately.
LD=Cp*Vd/F
Whats MD
Maintenance dose (MD) = The dose needed to maintain the given concentration within the therapeutic window when given repeatedly at a constant interval.
MD= CpssClt/F
Repeated dose administration
Cpss = concentration of drug in blood plasma at steady state
t int. = dosing interval
