Pharmocology principals

Question 1

what is apparent volume of distribution definition?

Answer 1

The theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma

Question 2

what is apparent volume of distribution formula?

Answer 2

Vd (liters)= amount of drug in body (Ab in mg)/ Plasma concentration (Cp in mg/L)

Question 3

What is the loading dose calculation?

Answer 3

Loading dose = Vd x desired Cp (volume of distribution x drug concentration in plasma)

Question 4

With protein bound drugs, what is measured when you do drug levels ?

Answer 4

Both the bound and Unbound portions

Question 5

With protein bound drugs, which part of the drug is active?

Answer 5

The free portion

Question 6

How does the plasma concentration increase with increased saturable drug doses compared to non saturable protein binding?

Answer 6

Less proportionally when compared to non saturable,, as the bound levels stays constant

Question 7

Where does most metabolism occur?

Answer 7

the liver

Question 8

Which notable 5 drugs decrease INR when used with warfarin (according to pharm lecture)?

Answer 8

Carbamazepine, phenytoin, rifampicin, cholestyramine, St john’s Wort.

Question 9

What is P glycoprotein’s function?

Answer 9

It is an efflux channel in the GIT, which normally functions to reduce absorption of drugs from the GIT

Question 10

what is the equation for clearance

Answer 10

Clearance (L/min) = (Vd x elimination constant)

Clearance (L/min) = Vd x 0.693/ t1/2

Question 11

What is the equation for steady state

Answer 11

Cpss = (bioavailability x dose) / dosing interval

Question 12

How long dose it take to reach steady state

Answer 12

5 x t1/2

Question 13

Which 5 drugs in the lecture have saturable metabolism and thus zero order kinetics

Answer 13

phenytoin, alcohol, theophyllin, aspirin, perhexilline

Question 14

What is the definition of a non competitive antagonist

Answer 14

Non competitive antagonist - binds irreversible to the receptor, max effect not achievable with agonist

Question 15

What is the definition of a competitive antagonist

Answer 15

binds reversibly to receptor, max effect still achievable with higher dose of agonist

Question 16

What is therapeutic range?

Answer 16

Therapeutic range is the difference between therapeutic effect and adverse effect

Question 17

What is efficacy determined by?

Answer 17

Determined by E max -( max effect - though usually use E50 ) Defined by curve height

Question 18

What is potency determined by?

Answer 18

Defined by dose at E max or E50 , Gradient and lateral position of curve

Question 19

What are the 3 main pharmacokinetic changes in the elderly ?

Answer 19

1. Decreased clearance (renal and hepatic function decrease), 2.Decreased Vd ( decreased muscle and water, more fat) 3. Decrease Protein binding (decrease albumin)

Question 20

What are the pharmacokinetic changes in preggars?

Answer 20

1. Clearance increased ( increase CO thus increased hepatic and renal blood flow), 2. Vd increases by 20% 3. Decreased protein binding ( lower measured drug levels, but free levels are unchanged)

Question 21

what is zero order kinetics

Answer 21

Constant amount of drugs is eliminated per unit time, Independent of total concentration in plasma, May occur when elimination enzymes are saturated Examples – phenytoin and alcohol

Question 22

What are the inducers of cytochrome p450?

Answer 22

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Carbemazepines, Cyclosporin
Rifampicin
Alcohol (chronic)
Phenytoin

Griseofulvin
Phenobarbitone
Sulphonylureas , St John’s Wort

Question 23

What are the inhibitors of p450?

Answer 23

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Valproate
Isoniazid
Cimetidine
Ketoconazole
Sulfonamides
Fluconazole
Alcohol (acute)
Chloramphenicol
Erythromycin (macrolides)
Amiodarone
Omeprazole
Grapefruit juice
Quinidine

Question 24

What is t1/2 calculation?

Answer 24

t1/2 = Vd*k

cl

( k= 0.7)