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Flashcards in Pharm Deck (14):
1

What is a drug?


A chemical substance that interacts with a biological system to produce a physiological effect

2

Target sites: 4

Receptors
Transporters
Ion Channels
Enzymes

3

List routes of administration: groupings

Entral (involves the GI tract): Oral, Rectal, Buccal, Sublingual

Parentral (doesn’t involve the GI tract): Intravenous, Intramuscular, Intradermal, Subcutaneous, Inhalation

4

What type of drugs will cross membranes?

Non-polar drugs (without charge) will cross the phospholipid bilayer as they are lipophilic (lipid soluble)

Polar drugs (with charge) cannot do this passively (ie. Need transporters)

5

Tell me about asprin

Aspirin is a weak acid pKa of 3.5

Acidic environment like the stomach pH of 2? has a high h+ concentration so does not need to contribute. Drug is unionised.

Alkaline environment like the intestine? will donate H+ ions and become ionised

Where is it preferentially absorbed?
STOMACH

6

Factos affecting distribution

Regional blood flow
Capillary permeability
Localisation in tissue
Extracellular binding

7

Excretion

Kidney (major): Most drugs ultimately eliminated here

Liver: Some drugs excreted here via biliary system (into gut).
Enterohepatic recycling: A drug or its metabolite is reabsorbed in the gut after biliary excretion and taken to the liver via the hepatic portal vein.

8

AIM OF METABOLISM IS TO Conversion of lipophilic chemicals to polar derivatives (so can’t be reabsorbed in kidney tubule)

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9

First pass metabolism

First pass metabolism is the metabolism of the drug in the body before it reaches the systemic circulation

10

Phase 1 vs Phase 2 Metabolism

Phase I
Oxidation/reduction creates new functional groups, hydrolysis unmasks them.
Important – functional group serves as a point of attachment for phase II reactions

Phase I reactions often inactivate chemicals, but can also activate (e.g. a prodrug).

After phase I metabolism, there is little change in polarity of the drug

USUALLY CYTOCHROME P450

Phase II
Uses conjugating agents
Conjugate is almost always pharmacologically inactive

More Polar

Easier to excrete

Glucuronidation, Acetylation, Amino acid conjugation, Sulphation, Methylation, Glutathione Conjugation

11

Bioavailability

proportion of administered drug that is available within the body to exert its pharmacological effect

12

Clearance

The volume of plasma cleared of a drug per unit time

13

Muscarinic receptors

M1 – Neural
M2 – Cardiac
M3 – Exocrine & smooth muscle

14

Apparent volume of distribution

the volume in which a drug appears to be distributed