Antibiotics presentation of Pharmaceutical Chemistry

Antibiotics presentation of Pharmaceutical Chemistry

1. ANTIBIOTICS
Prepared by: Ms. Lineeta K. Raut
PES Modern College Of Pharmacy (For Ladies),
Moshi, Pune.

2. LEARNING OUTCOME
•Definition
•Mechanism
•Classification
•Drugs chemical structure, IUPAC name, physical properties, uses, formulation and
brand names.

3. INTRODUCTION
Antibiotics are those chemical compounds which are produced by living micro-
organism that either inhibit the growth of micro- organism or kill other micro-
organism.
They act by different mechanism; penicillins and cephalosporins interfere with the
synthesis of bacterial cell wall.
Some antibiotics like streptomycin, tetracycline and chloramphenicol interfere with
various stages of protein synthesis.

4. SOURCES OF ANTIBIOTICS
Natural : Mainly fungal sources (e.g Benzylpenicillin and Gentamycin)
Semi synthetic: Chemically altered natural compound (e.g Ampicillin & Amikacin).
Synthetic: Chemically designed in the lab (e.g Moxifloxacin and Norfloxacin).

5. WHAT ARE THE ROLES OF
ANTIBIOTICS?
Bacteriostatic effect: To inhibit multiplication @ [drug] = (MIC) minimal inhibitory
concentration.
Bactericidal effect: To kill (destroy) the bacteria population @ [drug] = (MBC) minimal
bactericidal concentration. There is a much closer relationship between the MIC and
MBC values for bactericidal drugs than for bacteriostatic drugs.

6. WHAT IS AN IDEAL ANTIBACTERIAL?
Selective target – target unique
 Bactericidal – kills
 Narrow spectrum – does not kill normal flora
 High therapeutic index – ratio of toxic level to therapeutic level
 Few adverse reactions – toxicity, allergy
 Various routes of administration – IV, IM, oral
 Good absorption
Good distribution to site of infection
Emergence of resistance is slow

7. ANTIBIOTICS CLASSIFICATION
Depending on the basis of chemical structure:
a)ß-lactum antibiotic; e.g. Benzyl penicillin, phenoxymethyl penicillin, ampicillin
b)Non lactum antibiotics( does not contain beta-lactum ring)
These are further divided into following categories----
i)Antibiotics containing hydronaphthaline ring: e.g. tetracycline
ii)Aminoglycoside antibiotics: e.g. streptomycin, neomycin, gentamycin
iii)Macrolide antibiotics: e.g. erythromycin
iv)Ansamycins: e.g. Rifampicin
v)Polyene macrolide antibiotics: e.g. nystatin, hamycin, amphotericin B

8. vi) Anthracyclic antibiotics: e.g. actinomycin D, daunorubicin
vii) Peptide antibiotics: e.g. Bacitracin
viii) Steroidal antibiotic: e.g. fusidic acid
ix) Nucleoside antibiotics: e.g. puromycin
x) Other heterocyclic ring containing antibiotics: e.g. mitomycin, cycloserine
xi) Non- classifiable antibiotic: e.g. griseofulvin, chloramphenicol*

9. ß-LACTUM ANTIBIOTIC
•Due to the presence of highly strained ß-lactum ring in benzyl penicillin, it is
degraded rapidly in strong acidic and basic media.
•It is also inactivated by enzyme ( penicillinase) i.e. ß-lactumases and acylases
secreted by various bacteria. As it is inactivated by gastric juice, hence it should be
administered orally with antacids or strong buffers.
•When taken orally, it is poorly absorbed. Hence about five times more oral dose is
required than given by injection.

10. •Sodium and potassium salts are water soluble and are given parentrally. But
potassium salt is preferred to sodium salt, when patient is suffering from congestive
heart failure.
•It is eliminated rapidly from the body and hence it has to be given by injection
several times.

11. BACTERIA CELL WALL SYNTHESIS
•The cell walls of bacteria are essential for their normal growth and development.
•The peptidoglycan (which provide rigid mechanical stability) is composed of glycan
chains, which are linear strands of two alternating amino sugars (N-
acetylglucosamine and N-acetylmuramic acid) that are cross-linked by peptide
chains. (NAG-NAM).
•In gram-positive microorganisms, the cell wall is 50 to 100 molecules thick, but it is
only 1 or 2 molecules thick in gram-negative bacteria.

12. BASIC STRUCTURE OF PENICILLINS

13. Sr. no. Name of penicillin R=
1 Benzyl penicillin
2 Ampicillin
3 Phenoxymethyl
Peniciliin
4 Carbenicillin