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Semisynthetic penicillins - Coggle Diagram
Semisynthetic penicillins
Acid stable penicillins
By Including an electron withdrawing group on the side chain
Example: Phenoxymethyl makes penicillin V naturally orally active
Ex. Semisynthetic: Ampicillin & Amoxicillin
B- lactamase resistant penicillins
Bulky group in side chain causes steric hinderance to B-lactam ring, no hydrolysis by enzyme
Max. Resistance if R group is large ring structure
Methicillin
Bulky group
resist enzyme
electron donating so orally inactive
Nafcillin
Orally inactive
Oxacillin
pencillinase resistant
Orally active because electron withdrawing heterocyclic ring
Temocillin
Strong B lactamase resistance
orally inactive, by injection
broad spectrum
Extended/ broad spectrum
Addition of hydrophilic group allows penetration of lipophilic pores through
hydrophilic pores
ex. NH2 & COOH
a- amino group in a-position of side chain of penicillin high degree of acid stability together with high effect on G-ve bacteria
a- amino group is protonated in gastric juice
become EWG & acid resistant
ex. Ampicillin & Amoxicillin
Prodrugs of ampicillin
intended for increased oral absorption
Activated by esterase
Penicillins active Against pseudomonas
Introduction of very polar group in a- position of side chain
Increase G-ve effect & anti pseudomonas activity
not orally active, injection only
Carboxylic group esterified with ethanol to give orally active prodrugs of carbenicillian
B- Lactamase inhibitors
Inhibit B- Lactamase enzyme
Clavulanuc acid resemble normal penicillin but whey react with enzyme they alkylate enzyme causing irreversible inhibition
Augmentin = Amoxicillin + Clavulanic acid
Unacyn = Ampicillin + Sulbactam