hydrolysis

Question 1

stabiliy

Answer 1

is the capacity of a drug product to remain within specifications established to ensure its identity strength quality and purity

Question 2

instability may cause

Answer 2

-undesired change in performance (dissolution/bioavailibility)
-substantial changes in physical appearnace of the dosage form
-causing product failures

Question 3

factors affecting stability

Answer 3

-enviromental factors
-drugs or exciplents in the dosage form
-microbial contamination
-trace metal conatmination
-leaching from containers

Question 4

enviromental factors

Answer 4

temp
light
oxygen
moisture
carbon dioxide

Question 5

drugs or excipients in the dosage form

Answer 5

particle size of drug
-pH of the vehicle

Question 6

physical stability

Answer 6

-physical stability implies the formulation is totally unchanged throughout its shelf life and has not suffered any changes by the way of appearnece, organoleptic properties, hardness, brittleness, particle size, etc
-it is signifcant as it effetcs:
pharmaceutical elegance
drug content uniformly
drug release rate

Question 7

chemical stability

Answer 7

-chemical stability implies the lack of any decompositon in the chemical moiety that is incorporated in the formulation as the drug, preservatives or any other excipient
-this decomposition may influence the physical and chemical stabiity of the drug
-second although chemical degradation of the active drug may not be extensive, a toxic, product may be formed in the demcomposition process. there are several examples of the products of degradation are significantly more toxic than the original therapeutic agent
-third instability of a drug product can lead to a decrease in its bioavailibily, rather than to loss of drug or to formaltion of toxic degradation products

Question 8

hydrolysis

Answer 8

-the decomposition of a substance by the addition of water molecule is alled hydrolysis
-the reaction of anion/cat ion with water accompanied by the cleavage of OH- bond is called hydrolysis

Question 9

hydrolysis and condensation

Answer 9

hydrolyss can be reverse of a condensation reaction in which two molecuels join togehter into a large molecule and eject water molecule. Thus hydrolysis adds water to breakdown, whereas condensation builds up by removing water
ex) the hydrolysis of acetylsalicylic acids leads to formation of acetic acid and saicylic acids

Question 10

types of hydrolysis

Answer 10

on the basis of substrate, hydrolysis is classified into the following groups
-ionic hydrolysis
-molecular hydrolysis

Question 11

ionic hydrolysis

Answer 11

-that type of hydrolysis in which water reacts with the ions of salts (which are made up of weak acid or base)
-this is amphotyric type of hydrolysis, in which water either reacts as acid or base depending of the provided ion. the wate and ion react to form new acid and base
-as in this process transfer of proton is involved so also called protolysis

Question 12

molecular hydrolysis

Answer 12

-that type of hydrolysis in which water reats with a molecule of a compound is called molecular hydrolysis.
-due to this hydrolysis, decomposition of molecule takes place. For example: when aspirin is hydrolyzed it gives acetic acid and salicylic acid

types:
-ester hydrolysis
-amide hydrolysis
-ring hydrolysis

Question 13

functional groups subject to hydrolysis

Answer 13

-esters: aspiring, alkaloids, dexmethane, sodium phosphate, nitroglycerin
-lactones: pilocarpine, spironolactone
-amides: chloramphenicol
-lactancs: penicillins, cephalosporins
-imides: glutethimide

Question 14

effect of hydrolysis on drug stability

Answer 14

the process of hydrolysis has a great influence on the stability of the drug. As due to hydrolyis drug is decomposed and new products are formed, there new products may be toxic in nature and so decrease the therapeutic effect of drug. Moreover, the hydrolysis also decreases also decreases the attractivness of drugs. i.e.inelegant take place

Question 15

factors affecting hydrolysis

Answer 15

-moisture
-pH
-Temperature
-Solvent

Question 16

protection of drugs frm hydrolysis

Answer 16

various methods are used:
1-solid dosage form
2-liquid dosage form

Question 17

solid dosage form

Answer 17

-to the hydrolysis and to retain the activity of solid dosage forms, they are kept in air tight vessels
-and at the time of administration they are first dissolved in water and then used
-this process is called reconstitution and the product is called reconstitute product is pencilin and its derivatives are commonly used by this method

Question 18

liquid dosage forms

Answer 18

-the hydrolysis of liquid dosage forms is prevented by changing their pH with the addition of certain buffers
-by this not only an optimum pH of drug stabiiity is obtained but the therapeutic activity of drug is also retained

Question 19

complec formation

Answer 19

-some drugs are prevenetd from hydrolysis by comples such complexes not only prevent the process of hydrolysis but the therapeutic affect is also not effected
-for example when caffeine is added to benzoaince, caffeinebenzocaine complex is formed, which resist the hydrolysis of benzocaine, in this way its therapeutic activity is retained

Question 20

packaging and hygrocopic material

Answer 20

-the drugs are provided in such packiging which does not allow the water molecules to pass for this purpose, aluminium foils are used
-moreover, hydroscopic bags are placed in drugs which attract the water molecules or moisture and in this way hydrolysis may not take place

Question 21

pH of media

Answer 21

-some substances are more soluble in alkaline pH and basic drugs are more soluble in acidic pH
-so by changing the pH, their solubility is decreased and hence the hydrolysis of drug is prevented

Question 22

temperature

Answer 22

-all the drug products are stored at suitable temperatures to avoid thermal acceleration of decomposition. three varieties of temperature are suggested for storage of drug products.
-room temperature, cool storage, and cold storage

Question 23

light

Answer 23

light sensitive material are stored in ambered colour bottles

Question 24

addition of surfactans and solvent

Answer 24

solubilization of a drug by surfactants in many cases protects against hydrolysis

Question 25

removal of H2O

Answer 25

-hydrolytic decomposition may further be prevented by the removal of water
-the drug may be stored in dry form and used as such or suspended as an insoluble powder in a suitable vehicle
-even in the solid state, drug may decomposes ex) decomposition of soid aspirin due to temperature and humidity

Question 26

applications in pharmacy

Answer 26

1- many substances of pharmaceutical importance hydrolyze in the solution and give alaline and acidic solution that become the problem for magnification of pharmaceutics
2- salts of many alkaloids like ephedrine chloride and hyoscne chloride are weak bases
3- zinc sulphate, amerine hydrochloride in vitamin E yield acidic solution