The classification of Antitubercular and Antileprotic Drugs, and their mechanism of action.

1. Anti- Tubercular
and Anti-Leprotic
Drugs
Pratik Khanal

2. p-AminoSalicylic Acid (PAS)
• Mechanism of Action : PAS act as an
antimetabolite interfering with the incorporation
of the p-amino benzoic acid into Dihydrofolic
acid. The hydroxy dihydrofolate antimetabolite
inhibits Dihydrofolate reductase enzymatic
activity.
Antimetabolite: a substance that interferes with the normal
metabolic processes within cells, typically by combining with
enzymes.
Folic Acid: is a key metabolic component for the synthesis of
DNA, RNA and proteins.

3. N
N
N
N
Pteridine
+
O
HO
NH2
p-aminobenzoic acid
Dihydropteroate synthase
NH
N
O
NH
NH2
N
N
O
HO
Dihydropteroic acid
L-Glutamate
O
HO
HN
O
HN
N
O
HN
H2N
N
HN
O
HO
Dihydrofolic acid
Dihydrofolate synthase

4. O
HO
HN
O
HN
N
O
HN
H2N
N
HN
O
HO
Dihydrofolic acid
Dihydrofolate Reductase
O
HO
HN
O
HN
NH
O
HN
H2N
N
HN
O
HO
Tetrahydrofolic acid

5. Rifampin
Mechanism of Action :- Rifampin inhibit bacterial
DNA-dependent RNA polymerase (DDRP) by
binding to the β –subunit of the enzyme and are
highly active against rapidly dividing bacilli.
Inhibition of DDRP leads to blocking the initiation of
chain formation in RNA synthesis.

6. DNA Dependent RNA polymerase

7. Clofazimine (antileprotic)
Mechanism of Action: Clofazimine binds to
mycobacterial DNA, thereby blocking the
template function of the DNA and inhibiting
mycobacterial proliferation.
It has also been shown that generation of
antimicrobial reactive oxidants from neutrophils,
play a role in antileprosy effects.