Stability of drugs

Question 1

Ester containing drugs undergo slow hydrolysis under ______ conditions

Answer 1

neutral

Question 2

Hydrolysis can be catalysed by ____ or _____

Answer 2

acid

base

Question 3

Aspirin hydrolyses to _______ and ________

Answer 3

salicylic acid

ethanoic acid

Question 4

What are the storage conditions for ester containing drugs?

Answer 4

Airtight container to prevent access to moisture

Question 5

Amides and carbamates are more susceptible to hydrolysis than esters. True or false?

Answer 5

False

Question 6

Hydrolysis of an ester results in an alcohol and a carboxylic acid. True or false?

Answer 6

True

Question 7

The first step in acid-catalysed hydrolysis of esters is a substitution. True or false?

Answer 7

False - it is an addition step - the nucleophile is added (water)

Question 8

The second step of an acid catalysed hydrolysis is elimination (of ethanol) followed by elimination of proton True or false?

Answer 8

True

Question 9

In base catalysed hydrolysis of esters the first step is addition of electrophile. True or false?

Answer 9

False - addition of nucleophile

Question 10

The overall mechanism for base catalysed hydrolysis of esters is substitution. True or false?

Answer 10

True - first step is addition, second step is elimination

Question 11

What makes the C=O if an amide less susceptible to attack by nucleophiles?

Answer 11

Resonance

Question 12

Why is the 4-membered cyclic amide in Penicillins prone to hydrolysis?

Answer 12

Steric strain in the ring

Question 13

Why do penicillins need to be stored in the fridge?

Answer 13

Susceptible to hydrolysis

Question 14

Radicals can form from OH, NH and CHs. True or false?

Answer 14

True

Question 15

Free radical oxidation is a problem for phenolic drugs especially the catechol group. True or false?

Answer 15

True

Question 16

FRO is a problem for aromatic amines and unsaturated aliphatic compounds. True or false?

Answer 16

True

Question 17

The process of FRO is more rapid at low pH. True or false?

Answer 17

False - rapid at high pH

Question 18

Which hormone contains a catechol group formulated as the tartaric acid salt to keep it acidic (and minimise FRO)?

Answer 18

Adrenaline

Question 19

Absorption of energy can promote the electrons in a bond to an ‘excited state’ generating ______

Answer 19

radicals

Question 20

How do you prevent light from forming FRO in medicines?

Answer 20

Store medicines in foil packaging or brown bottles

Question 21

Transition metals can accept an _______ and initiate radical formation

Answer 21

electron

Question 22

How do you prevent metals from forming FR?

Answer 22

Add a metal chelating agent e.g. EDTA

Question 23

Fe3+ + e- -> ____

Answer 23

Fe2+

Question 24

In the presence of light, oxygen forms ________ radicals that give rise to oxidation and degradation of medicines

Answer 24

peroxide

Question 25

How do you prevent FR formation from oxygen?

Answer 25

Store medicines in a well filled, well closed container

Add another gas e.g. Nitrogen

Question 26

How do antioxidants prevent radical formation?

Answer 26

They trap radicals, preventing their self-propagation.

They mop up radicals or form stabilised radicals that do not continue the chain

Question 27

BHT, Vitamin E, Vitamin C are e.g.s of ?

Answer 27

antioxidants