* Pharmacology - 2 (4) Flashcards
(43 cards)
What most drugs leave the body in?
Where else are drugs excreted via? (3)
Urine (excretion via the bile is occasionally significant + minor contributions via exertion via the sweat or milk)
What kind of molecule must drugs be to be excreted by the body?
Why?
Polar
So that they can be regularly reabsorbed by the kidney facilitating excretion
What is a xenobiotic?
A foreign chemical substance that is found within an organism that is not naturally produced by or expected to be present within that organism
What does metabolism usually do in terms of rendering the activity of the drug?
What are 3 other things that metabolism less rarely does to drug activity?
Usually make the drug less pharmacologically active
Converts them from inactive to active compounds or gain activity
Have unchanged activity
Possess a different type, or spectrum of action
What is an example of a drug that gains activity during metabolism?
Codeine to morphine
What is an example of a drug that has unchanged activity after metabolism?
Diazepam to nordiazepam
What is an example of a drug that possess a different type, or spectrum, of action after metabolism?
Aspirin (anti-inflammatory and andti-platelet) to salicylic acid (anti-inflammatory with no anti-playlet activity)
What is the main organ of drug metabolism?
What other places have metabolism activity? (3)
Liver
GI tracy
Lungs
Plasma
How many steps does drug metabolism usually have?
2 sequential steps
What is the purpose of phase 1 drug metabolism?
To make the drug more polar and also to add a chemical “handle” permitting conjugation during phase 2
What are the 3 things involved in phase 1 drug metabolism?
Oxidation
Reduction
Hydrolysis
What is the purpose of phase 2 drug metabolism?
To add an endogenous compound increasing polarity for excretion
What is the 1 thing involved in phase 2 drug metabolism?
Conjugation
some drugs skip straight to phase 2 whilst some drugs are excreted unchanged
What are examples of the chemicals that are drugs are conjugated with during phase 2 drug metabolism?
Glucuronyl
Sulphate
Methyl
Acetyl
What are the 2 phases of drug metabolism of aspirin (acetylsalicylic acid)?
Aspirin is converted to salicylic acid (OH added) before being converted to the conjugate (glucuronide) during phase 2
What are the cytochrome P450 (CYP) family of monooxygenases?
Haem porteins located in the endoplasmic reticulum of liver hepatocytes (and elsewhere) mediating oxidation reaction (phase 1) of many lipid soluble drugs
How many gene families is the Cytochrome P450 family of monooxygenases made up of?
74 gene families - it is a superfamily
what are the main 3 gene families in the liver?
CYP1
CYP2
CYP3
What are 3 examples of common cytochrome P450s?
CYP3A4 - accounts for 50% of metabolism of all presciription drugs
CYP2D6
CYP2C
What are the basics of what happens in the monooxygenase P450 cycle?
Drug enter the cycle as a drug substrate, RH
Molecular oxygen (O2) provides 2 atoms of oxygen
One atom of oxygen is added to the drug to yield the hydroxyl product (ROH) which leaves the cycle
The second oxygen combines with protons to form H2O
this is mediated by monooxygenases
In phase 2 reactions, what type of groups on the drugs are the endogenous molecules commonly added to?
Chemical reactive groups e.g. hydroxyl (OH), thiol (SH) or amino (NH2)
What is a common reaction in phase 2 that tends to detoxify most drugs?
Glucuronidation
What does glucuronidation commonly involve?
The transfer of glucuronic acid to electron-rich atoms on the drug (such as N, O or S ) forming amide, ester or thiol bonds
what enzyme mediates glucuronidation?
UDP-glucuonyl transferase
