Excretion

Question 1

what organs are involved in the elimination of drugs in the system

Answer 1

Kidney, Liver, Lungs, intestinal tracts, and other (milk, sweat, tears, etc)

Question 2

breifly describe the renal excretion (kidneys)

Answer 2

it receives 20% of cardiac output, glomerular capillaries highly porous and permeable, which allows for filtration of undound drugs is a non-saturable and non-selective process.

Question 3

what kind of drugs are eliminated by the Renal system?

Answer 3

Polar drugs, and drug metabolites

Question 4

Describe active tubular secretion, and which bodily system its connected with?

Answer 4

occurs with Renal excretion, and its where transporters in proximal tubules actively pump a minority of drug types into urine, its also saturable.

Question 5

describe tubular reabsorption, and which bodily system its connefcted with?

Answer 5

occurs with Renal extractions, and its where active tranporters present in distal tubules reabsorb some filtered drugs from provisinal urine. Lipid-soluble un-ionized drugs are reabsorbed passively (diffuse out of tubule back into bloodstream)

Question 6

What mathematical method can be used to describe the elimination process

Answer 6

half-life, which is the time required for the drug to decrease by 50%. Its a result of the 1-step-first-order process
*it does not depend on dose of drug concentration

Question 7

After how many half lifes is a drug usually eliminated from the body

Answer 7

4-5 half-lifes

Question 8

what two factors much be considered through drug administration, related to half-lifes and blood concentration

Answer 8

the minimum toxic concentration be avoided, and the minimum effective concentation should be maintained.

Question 9

when dealing with substantial half-life concentrations, with continuous administration, which method of administration is best?

Answer 9

and IV drop allows a slow and long administration

Question 10

does the time taken to achieve a steady state depend on the rate at which the drug is administered?

Answer 10

no

Question 11

describe the ratio between chronic dosing, and rate of administration

Answer 11

the steady state plasma drug concentration (Css) is directly proportional to the rate of drug administered. there fore if double the rate of admin then you double the Css

Question 12

how can Css be reached more rapidly?

Answer 12

if the initial dose is larger than the subsequent doses (called a loading dose)

Question 13

what happens if the excretion rhythm is decreases (eg. renal failure)

Answer 13

then the drug-half like increases, therefore you must decrease the dose of increase he dosing interval.

Question 14

how can you alternate the new time interval (mathematical equation used in definition)

Answer 14

you can do this based on serum creatinine.

the new interval is the usual interval multiplied by (the patient creatinine divided by the normal creatinine)

Question 15

how much of a drug is eliminated in 5 half lives? in 10 half-lifes?

Answer 15

1. 5= 97%

2. 10=99.9%

Question 16

how can you minimize the differece between peak and through drug concentrations?

Answer 16

by giving smaller doeses more frequently

Question 17

where do we want the drug through concentration to remain?

Answer 17

above minimum effective concentrations (MEC) and peak levels below minimum toxic concentration (MTC)

Question 18

what is enterohepatic recycling?

Answer 18

its when some conjugated drugs can be deconjugated by gut bacteria -> reabsorbed into the blood

Question 19

what is hepatic excretion?

Answer 19

the drugs that are conjugted via phase 2 metabolism are excreted into the bile (active transport )-> into the gut -> feces

Question 20

what can cause adverse effects, in relation to a therapeutic margi?

Answer 20

Essentially all drugs have more than one effect in the body, and too much can be toxic. The adverse effects can be due to excessive receptor stimulation, or stimulation of other receptors.

Question 21

what is ment when a drug is said to have a wide theraputic margin
?

Answer 21

it referes to the drugs that produce toxicity at doses much higher than those required for desired effect.

Question 22

what kind of drug are barbiturates?

Answer 22

theres are drugs that produce toxicity at doses close to those required for therapeutic effect to have a narrow therapeutic margin.

Question 23

what is clearance? and what is its purpose?

Answer 23

(volume/unit time/Kg body weight) its the apparent complete removal of drug from a certain volume of plasma per unit of time per unit of body weight.
and it gives and indication of efficiency of elimination of drug from plasma.

Question 24

what routes are involved in total systematic clearance?

Answer 24

elimination of drug via liver, kidney, others (all)

Question 25

what are the application purposes of clearance?

Answer 25

its used to clinically to calculate dosing rate and maintenance doses to maintain a target drug concentration(TC).
dosing rate =CL (clearance rate) x TC (target concentration)

Question 26

how do you calculated maintenance dose?

Answer 26

MD= (dosing rate/F) * dosing interval 
F= bioavailability