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BDS2 BAMS pharmacology > drug administration > Flashcards

Flashcards in drug administration Deck (20)
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1

what are the stages drugs go through in the body?

administration
absorption
transport
clinical effect
metabolism
excretion

2

what are the advantages of oral drug administration?

socially acceptable
drug formulation can change onset and duration of action

3

what are the disadvantages of oral drug administration?

slow onset
variable absorption
-food interactions in GIT
-GI disease
-gastric acid may destroy drug
first-pass metabolism

4

what is first pass metabolism?

all blood from GIT drains to hepatic portal vein
-except sublingual and rectal veins
hepatic portal vein drains to LIVER
-liver metabolises contents
-drug only reaches systemic circulation after passing through the liver once
can inactivate or activate a proportion of the drug
-varies with liver disease & age

5

give an example of a drug that the liver metabolism inactivates

glyceryl trinitrate (GTN)
more needed by oral route to get desired clinical effect

6

give an example of a drug that the liver metabolism activates

valaciclovir aciclovir
makes an active form of an inactive drug
less needed by oral route

7

what are the advantages of IV/IM administration?

very rapid onset
predictable plasma levels
no 1st pass metabolism

8

what are the disadvantages of IV/IM administration?

allergic reactions more severe
short duration of action
access difficulties/self-medication
drug cost higher

9

what are the advantages of transdermal & subcutaneous administration?

no 1st pass metabolism
allergic reactions localised
prolonged action
-can be days with transdermal patches

10

what are the disadvantages of transdermal & subcutaneous administration?

very slow onset
self-medication possible
drug cost higher
effect will vary from person to person and site to site

11

what is bioavailability?

proportion of an ingested drug that is available for clinical effect

12

what is bioavailability modified by?

dosage form
route of administration
destruction in the gut
poor absorption
first pass metabolism

13

how are drugs distributed?

drug is dissolved in the blood and transported bound to carriers
-usually plasma protein albumin

14

what can happen when drugs bind to plasma proteins?

bound drug is inactive so can act as a reservoir
drug interactions possible by competitive binding
-warfarin & aspirin

15

what does the speed of diffusion into tissues from the blood depend on?

the blood flow to the area
the blood wall vessel barrier
active secretion of the drug into the tissue

16

what is the single compartment model?

drug behaves as if it is evenly distributed throughout the body

17

what is the two compartment model?

drug behaves as if it is in equilibrium with dif tissues in the body

18

what is volume of distribution?

some drugs actively secreted into tissues or fluid rather than simple diffusion

19

why may dif parts of the body receive dif drug levels compared with plasma-compartment model?

drug selection may depend upon the preference of some drugs for some areas of the body
eg. vascular, tissues, CNS

20

why do some drugs have significant lipid binding in the tissues?

slow release from accumulation-prolonged effect
eg. anaesthetic gas
-halothane, isofluorane