This document discusses chemical degradation, specifically hydrolysis, as a type of chemical degradation of drugs. It defines hydrolysis as the reaction of water with another chemical compound to form two or more products, involving the ionization of water and splitting of the other compound. The document outlines the main types of hydrolysis as ester hydrolysis, amide hydrolysis, and ring hydrolysis. It provides examples of drugs that undergo each type of hydrolysis, such as tetracaine undergoing ester hydrolysis and dibucaine undergoing amide hydrolysis. The document also notes that hydrolysis can be retarded through various approaches to protect drugs against this degradation pathway.

1. 1

2. PRESENTED BY:
TASNEEM RASHID
CLASS:1st PROFESSIONAL(EVENING)
ROLL NUMBER:DE-092
INSTITUTE:HAMDARD UNIVERSITY (FACULY OF
PHARMACY)
SUBMITED TO:
MAM TEHMINAADNAN
REFRENCE:
BOOK:PHYSICAL PHARMACY (AS PER B.PHARM SYLLABUS OF AICET)S.P.AGARWAL RAJESH KHANNA
EDITION: SECOND EDITION)
CHAPTER NUMBER : 8 KINTETICS AND DRUG STABILITY
PG NUMBER: 243-245
2

3. CHEMICAL
DEGREDATION
3

4. CHEMICAL DEGRADATION:
It is the seperation of chemical compounds into elements or simpler
compounds.change in the chemical nature of drug is called as chemical
degradation.
4

5. TYPES OF CHEMICAL
DEGRADATION:
 Hydrolysis
 Oxidation
 Decarboxylization
 Isomerization
 Polymerization
5

6. HYDROLYSIS
6

7. HYDROLYSIS:
 DEFINATION:The reaction of water with another chemical compouds to
form to or more products, involving ionization of water molecule and
usually splitting of other compounds
 EXAMPLE:The catalyic conversion of starch to glucose, sponification and
formation of acids and bases from dissolved ions
7

8. MECHANISM OF HYDROLYSIS:
8

9. TYPES OF HYDROLYSIS(ON BASIS OF
CHEMICAL REACTIONS):
It has two types:
 Ionic hydrolysis
Occur when salt of weak acid and base intreact with water to give either acidic
or alkaline solution.
EXAMPLE:CH3COOK give alkaline while codein phosphate give acidic
solution when intreact with water.
 Molecular hydrolysis:
Involve the cleavage of drug molecule.It is much slower and irreversible
process.It is catalysed by hydroxyl or hydrogen ion and specifically acid
and base catalysed.Rate of decomposition depend upon the pH of system.
EXAMPLE:The local anesthestics,amethocain,benzocain.
9

10. TYPES OF HYDROLYSIS:(ON THE BASIS OF
DRUG DEGRADATION)
 Hydrolysis is usually catalysed by hydrogen ion(specific acid hydrolysis)or
hydroxyl ions(specific base catalysis)and also by other acidic or basic
species commonly encountered as components of buffers.
 There are three types of hydrolysis
 Easter hydrolysis
 Amide hydrolysis
 Ring hydrolysis
10

11. ESTER HYDROLYSIS:
The most common type of ester hydrolysis reactios involve acyl-oxygen
cleavage.The ester hydrolysis whether acid or base catalysed can be
represented as:
O O
II II
R-C-OR + H2O--------- R-C-OH +HOR + HOR
(ESTER) (ACID) (ALCOHOL)
11

12. EXAMPLES OF DRUGS WHICH UNDER
GOES ESTER HYDROLYSIS:
1. Tetracaine
2. Atropine
3. Physostigmine
4. Procaine
5. Asprin
12

13. RING HYDROLYSIS:
Hydrolytic reactions in certain drugs proceed by ring cleavage with
subsequent attack by hydrogen or hydroxyl ions.
DRUGS UNDER GO RING HYDROLYSIS:
 Bezodiazepines(such as nitrazepam and chlordiazepoxide)
 Penicillins
 cephalosporins
13

14. AMIDE HYDROLYSIS:
Although amides are relatively more stable than esters,these are also
susceptible to specific and general acid-base hydrolysis.Amides hydrolysis
usually involves the cleavage of the amide linkage to given an amine
instead of an alcohol as in case of ester hydrolysis.The amide hydrolysis
reactions can be represented as:
O H O
II I II
R-C-N-R +H2O↔ R-C-OH + H2N-R
(AMIDE) (AMINE)
14

15. EXAMPLES OF DRUGS WHICH UNDERGO AMIDE
HYDROLYSIS:
1. Dibucaine
2. Ergometrine
3. Chloramphenicol
4. Niacinamide
5. Barbiturates
15

16. PROTECTIONAGAINST
HYDROLYSIS:
Hydrolysis or solvolytic reactions may be retarded by the following approaches:
16

17. THANK YOU
17