Drug Excretion

Question 1

Renal excretion Equation ?

Answer 1

(Glomerular filtration + Tubular secretion) - Tubular Reabsorption

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Question 2

Glomerular filtration factors ?

Answer 2

1. Molecular weight- <10000 dalton
2. Conc of drug in plasma
3. RBF(+) Drug excretion(+)
   4.GFR (+) Drug excretion(+)
   5.Neutral drug- rapidly filtered
   6.Plasma protein bindings—————Only free drugs

but if bind to ALBUMIN its conc will be less than tha total plasma conc

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Question 3

Tubular secretion factors ?

Answer 3

1. PCT — (Plasma-Lumen) =Drug

1.Acidic/Anionic transport protein
glycine sulphate glucoronic acid

2.Basic/Cationic transport protein
morphine amiloraide histamine ethambutol cathecolamines

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Question 4

Tubular reabsorption ?

Answer 4

Lumen———–DCT

1.Lipid soluble drug=More reabsorbed
2.Water soluble drug = More excreted
3.acidic drug = acidic urine = more reabsorbed
4.alkaline drug = alkaline urine = more reabsorbed
5.acidic drug = alkaline urine = more excreted
6.alkaline drug = acidic urine = more excreted

Question 5

Imporatnce of Biliary Excretion >?

Answer 5

1.Due to ENTEROHEPATIC cycling= drugs which are in biliary route =Inc duration of drug action
2.Liver f= biliary excretion hampered = drug conc inc = toxicites

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Question 6

Prolongation of drug action ?

Answer 6

1. inc plasma protein binding
2. inc frequency
3. inc dose
4. inc absorption from the route of administration

5.dec rate of distribution
6.dec rate of metabolism
7.dec renal excretion
8.dec gut motility

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