The document discusses various types of impurities in drug substances, categorizing them into organic and inorganic impurities, and residual solvents. It outlines classifications of solvents based on their toxicity, detailing Class 1 solvents to be avoided due to high toxicity, Class 2 solvents to be limited, and Class 3 solvents with low toxic potential. Additionally, it provides concentration limits and permissible exposure levels for various solvents as per ICH guidelines.

2. Organic Impurities
⚫ Starting materials
⚫ By-products
⚫Intermediates
• Degradation products
Reagents, ligands and catalysts
Inorganic Impurities
Reagents, ligands and
catalysts
• Heavy metals or other
residual metals
. Inorganic salts
. Other materials (e.g., filter
aids, charcoal)
Residual Solvents
Class 1 Solvents
⚫
To Be Avoided
⚫ Class 2 -
Solvents To Be
Limited
⚫ Class 3-Solvents
with Low Toxic
Potential
Types of Impurities
Solvents To Be
Avoided
Solvents To Be Limited Solvents with Low
Toxic Potential

3. Organic Impurities
• Organic impurities mainly arise during the synthesis,
purification(manufacturing process )and or storage of the drug substance
⚫ Organic impurities can be classified like....
✓ Starting materials
✓ Intermediate
✓ Degradation products
✓ Reagents, ligand and catalysts

4. Inorganic impurities derive from the manufacturing process
and excipients
the, cadmium, chromium, copper, iron, lead, mercury,
nickel and sodium.
Sometimes they might present in the product during
processing or they leached from packing
material Generally, excipients contain high levels of
heavy metals such as arsenic, bismuth
✓ Heavy metals
✓Inorganic salt
✓Other materails like filter aids, charcoal
Inorganic impurities

5. Residual solvents (ICH Q3 C guideline)
• Residual solvents are potentially undesirable substances. They
either modify the properties of certain compounds or may be
hazardous to human health.
• The residual solvents also affect physicochemical properties of
the bulk drug substances such as crystallinity of bulk drug,
which in turn may affect the dissolution properties, odor and
color changes in finished products
Residual solvents are those solvents which are used as
vehicles for the preparation of solution / suspensions in
the synthesis of a new drug substance

6. As per the ICH guidelines, the solvents used in the
manufacturing of drug substances classified in to four types
• Class 1 solvents: Solvents to be avoided
• Class 2 solvents: Solvents to be limited
Class 3 solvents: potential Solvents with low toxic
Class 4 solvents: Solvents for which No Adequate Toxicological
Data was Found

7. a) Class I solvents: Solvents to Be Avoided
Solvents in Class 1 should not be employed in
the manufacture of drug substances,
excipients, and drug products because of their
unacceptable toxicity or their deleterious
environmental effect.
However, if their use is unavoidable in order
to produce a drug product with a significant
therapeutic advance, then their levels should
be restricted as shown in Table 1.

8. Residual solvent Concentration limit (ppm)
Benzene 2 (Carcinogenic
Carbon tetrachloride 4 (Toxic
1,1 Dichloroethane 8 (Toxic)
1,2 Dichloroethane 5 (Toxic)
1,1,1 trichloro ethane 1500 (Environmental
hazard
Table 1.
b) Class II solvents: Solvents to Be Limited Class II solvents usage should
be
limited in pharmaceutical products because of their inherent toxicity.
Table 2 lists class II solvents with their daily permissible exposure.

9. Solvent PDE (mg/day) Concentration limit (ppm)
Acetonitrile 4.1 410 Chlorobenzene 3.6 360 Chloroform
0.6 60 Cumene 1 0.7 70 Cyclohexane 38.8 3880 1,2-
Dichloroethene 18.7 1870 Dichloromethane 6.0 600
1,2-Dimethoxyethane 1.0 100 N,N- Dimethylacetamide
10.9 1090 N,N-Dimethylformamide 8.8 880 1,4-Dioxane
3.8 380 2-Ethoxyethanol 1.6 160 Ethylene glycol 6.2
620 Formamide 2.2 220 Hexane 2.9 290 Methanol 30.0
3000 2- Ethoxyethanol 0.5 50 Methyl butyl ketone 0.5
50 Methylcyclohexane 11.8 1180
Methylisobutylketone2 45 4500 N- Methylpyrrolidone3
5.3 530

10. c) Class III Solvents: Solvents with Low Toxic Potential These are
less toxic and possess lower risk to human health than class I or
class II
• Long-term toxicity or carcinogenicity not reported, which is
evident from the available data for the solvents under this
category. The use of class III solvents in pharmaceuticals does
not have any serious health hazard.
Some of the solvents are; Acetic acid, anisole, butanol,
2butanol, isopropyl acetate, methyl acetate, butyl acetate,
Ter-butyl methyl ether, pentene, cumene, Dimethyl sulfoxide,
ethanol, ethyl acetate, formic acid, formic acid, heptane,
isobutyl ketone, tetrahydrofuran, 1-pentanol, 2propanol, methyl
isobutyl ketone, propyl acetate, 3methyl- 1-butanol, methyl
ethyl ketone.

11. THANK YOU
CREATED BY VIJAY KUMAR