Antibiotics simplified

Antibiotics

By :

Abdullah Taskin -4th year med. Student -

BY : Abdullah Taskin 4th y.

•Classified according to their MOA into :


Penicillin's

1. Benzyl penicillin 2. Aminopenicillin (ampicillin IV - amoxicillin PO)3. Isoxozoyl penicillin (cloxacillin, methicillin, ) 4. Ureidopenicillin ( piperacillin ) 5. Lactamase Inhibitors (Augmentin – tazobactam ) 6. Cephalosporins ( 1 , 2 , 3 & 4 ) 7. Carbapenems (imipenem ) 8. Vancomycin (Vancocin®)


penicillin Coverage :

GP exceptStaphylococcus, Enterococcus

Oral anaerobes(except

Bacteroides, Treponema)

MOA :Bactericidal:

β-lactam inhibits (PBP) and

prevents cross-linking of

peptidoglycans

Indications:actinomycosis, streptococcalpharyngitis,

streptococcal skin and soft

tissue infections, syphilis

Contraindications:Hypersensitivity to

penicillinBY : Abdullah Taskin 4th y.

Aminopenicillin( Amoxicillin )

Coverage :sam as

B.penicillin

MOA :sam as

B.penicillin

Indications:bacterial meningitis ,

endocarditis , streptococcal ,

part of H. pylori treatment, UTI



Isoxozoyl penicillin(methicillin )

Coverage :sam as B.penicillin

MOA :sam as B.penicillin

Indications ( only diff. ) :also cover some staph.a


Penicillin&

> Interstitial nephritis


Ureidopenicillin(Tazocin®)

Coverage :sam as

B.penicillin

MOA :sam as

B.penicillin

Indications :Same as penicillin &GN: Pseudomonas

Anaerobes

Enterococcus



Lactamase Inhibitors (Augmentin®)

Coverage :sam as B.penicillin

MOA :sam as B.penicillin

Indications :Same as penicillin

+/&Staphylococcus

H. influenzaeEnterococcus


Penicillin&

jaundice or hepatic

dysfunction


Cephalosporins ( 1 , 2 , 3 & 4 )

widely used


Coverage :GP except

Enterococcus&

GN exceptE. coli,

Klebsiella, Proteus

MOA :same as penicillin

(B-lactam)

Indications:GP “more” & GN

Contraindications:

Hypersensitivity to Penicillin or ceha.S.

&Nephrotoxicity

Ceph.S. 1st

(cephalexin , cefazolin)


Coverage :GP week

& GN&

anaerobes


(B-lactam)


Penicillin or ceha.S.

Ceph.S. 2nd (Ceftin®) , Cefprozil (Cefzil®))


Coverage :GP

Staph & strep.&

GNbroad

+ pseudomonas


(B-lactam)

Indications:RTI, gonorrhea (use cefixime),

meningitis, septicemia, abdominal infections



Ceph.S. 3rd

(cefixime, ceftriaxone , cefotaxime& ceftazidime )


Coverage :(good for gram +ve and –ve)

& pseudomonas

“penetrates the CSF”


(B-lactam)



Ceph.S. 4th

(cefepime)


Cephalosporins (β-Lactam) :

a) Renal elimination

b) Ceftriaxone & Cefoperazone biotransformation in the liver.

c) Thrombocytopenia associated with cefamandole and cefoperazone NOT cefotetan!!

d) Pyrogenic (highest rates of drug induced fever)


Coverage :GN only

& work with

aminoglycosides

MOA :(B-lactam)

Indications:patients who are allergic to penicillins

or cephalosporins

Contraindications:

Not allergic .

Monobactams β-Lactam Aztreonam


Coverage :GP except

Enterococcus, MRSA

GN includingPseudomonas + Enterobacter

Anaerobes

MOA :(B-lactam)

Indications:LARGEST SPECTRUM OF ACTIVITY of any B-lactam

Rx: Septicemia of unknown origin

Major disadvantages:metabolize by kidney > cause decreased urinary

concentration. SE: seizers ,rashso IMIPENAM + CILASTATIN (inhibitor of

enzyme) are given

together.

Carbapenams β-Lactam:(Imipenam )


Coverage :GP except

Enterococcus, MRSA

GN includingPseudomonas + Enterobacter

Anaerobes

MOA :(B-lactam)

Major disadvantages:not need CILASTATIN

&Less seizures

Carbapenams β-Lactam:(meropenem )


Coverage :GP (strong)

MOA :Glycopeptide

stearicallyinhibits addition of

peptidoglycan subunits

Indications:GP: (RESISTANT to methicillin)

e.g. MRSA & MRSEmust be given IV NO GI

Major disadvantages:Red Man Syndrome

, Nephrotoxicity , Ototoxicity , Neutropenia, Thrombocytopenia

NON β-Lactam:( VANCOMYCIN )


Coverage :Gram +ve and –

ve spectrum

MOA :inhibit cell wall

Indications:SINGLE DOSE Of uncomplicated UTI :

treatment of ONLY IN FEMALES!!

NON β-Lactam:(FOSFOMYCIN )


Contraindicated in pregnancy

1. Aminoglycosides

2. Erythromycin

3. Clarithromycin

4. Tetracyclines

5. Fluoroquinolones


Protein synthesis inhibitors :


Protein synthesis inhibitors

50 S 30 S

A- Macrolides B- Lincosamides

1) Erythromycin

2) clarithromycin

3) azithromycin

1) clindamycin

2) Chloramphenico

3) linezolid

1- Aminoglycosides

2- Tetracyclines


Coverage :GP except

Enterococcus&

GN“Atypicals”

MOA :inhibit 50 S

Indications:Clarithromycin = H.pyloricAzithromycin = Co-drug of choice for Chlamydia & Safe in pregnancy .

Major disadvantages:GI upset , acute cholestatic hepatitis

Prolonged QTHypersensitivity

Macrolides


Coverage :GP except

Enterococcus&

Anaerobes

MOA :inhibit 50 S

clindamycin =Pseudomembranous colitisChloramphenicol= Aplastic anemia & Grey baby syndrome

linezolid = HTN , myelosuppressionoptic neuropathy, peripheral neuropathy

clindamycin


Coverage :GN &

psudomonas

MOA :inhibit 30 S

Indications:G - & no alternatives .

Major disadvantages:Nephrotoxicity

Ototoxicity

Aminoglycosides


Coverage :GP

AnaerobesAtypicals:

Chlamydophila, Mycoplasma,Treponemaprophylaxis

MOA :inhibit 30 S

Indications:Rickettsial infections, Chlamydophila, acne malaria prophylaxis (doxycycline).

Major disadvantages:Hepato-renal toxicity, Fanconi’s syndrome,

Photosensitivity, Teratogenic, Yellow teeth and stunted , bone growth in children,( not in preg.)

Tetracyclines


Coverage :Poor GP activity

GN

AtypicalsFIncludes anaerobes

No Pseudomonas coverage

except : ciprofloxacin

MOA :Inhibits DNA gyrase

Dysglycemia

Indications:Only use when necessaryto prevent resistance

Major disadvantages:Allergy , Seizures , Prolonged QT

TOPOISOMERASE INHIBITORS :Fluoroquinolones


Coverage :GPC

N. meningitidisH. influenza

Mycobacteria

MOA :Inhibits RNA polymerase

Indications:TB , latent TB , Endocarditis & prophlaxis N. meningitides exposure

Major disadvantages:Hepatic dysfunction, P450, Orange

tears/saliva/urine & Jaundice

TOPOISOMERASE INHIBITORS :Rifampin


Coverage :AnaerobesProtozoa

MOA :Forms toxic

metabolites inbacterial cell which

damagemicrobial DNA

Indications:Protozoal infections(trichomonas, amebiasis,giardiasis), bacterial vaginosis, anaerobic bacterial infections

Major disadvantages:Seizures

Peripheral neuropathy ,

TOPOISOMERASE INHIBITORS :Metronidazole (Flagyl®)


Coverage :GP

GN: entericNocardia

Other: Pneumocystis,Toxoplasmosis

MOA :Inhibits folic acid

production(TMP inhibits DHFR and

SMX is a competitive inhibitor of PABA)

Major disadvantages:Hepatitis , Stevens Johnson syndromeTMP:- Megaloblastic anemia- Leuko/granulocytopenia- HyperkalemiaSMX:- Hypersensitivity- Interstitial nephritis- BM suppression

ANTI-METABOLITE:Trimethoprim- Sulfamethoxazole

(TMP/SMX)


Remain :

• Antimyobacterial ( rifampicin covered above )


Appendix


Basic : G.ngative vs. G.positive


Properties of penicillin :• All penicillin has Beta lactam ring .

• Trans-peptidase or (penicillin-binding protein)• Function : Synthesis of peptidoglycan layer .

• To be effective Penicillin must :

I. Penetrate cell layer II. Keeps it beta lactam ring intact III.Bind to Trans-peptidase .


How bacteria defended from penicillin ?

In three ways :

1) G. negatives prevent penetration of cell layers by alteration of porins.

2)G. negatives destroy beta-lactam in periplasmic space .

3) Bacteria inhibit binding of B.lactam to trans-peptidase by altering structure of Trans-peptidase .


References :

• Ananthanarayan & Pinker’s 8th edition .

• Clinical Microbiology Made Ridiculously Simple – 3rd edition


Thank you …


Antibiotics simplified

Health & Medicine

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