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Created by Qosru Iskandariah

Mechanisms of antibacterial agents

Cell wall inhibitor

Penicillin

Class Penicillin G Depot Preparation Acidic ResistantPenicillin (Penicillin

V)

B-LactamaseResistant Penicillin(Antistaphylococcal

penicillin)

ExtendedSpectrumPenicillin

AntipseudomonalPenicillin

Characteristics -Greatest activity againstgram ve and gram+ve andother non-B lactamaseproducing organisms-Penicillinase hydrolysespenicillin into peniciloicacid

1. Procaine penicillin(600.000 U every 18-24 hours)2. Benzathinepenicillin(1.200.000/2.400.000U) used for 1 monthonly for purpose of prophylaxis

-Probenecid blocksrenal excretion of penicillin

-Oral form of penicillin (acid stable)

-Effective againststaphylococcal andstreptococcal-They include:1. Nafcillin2. Oxacillin3. Cloxacillin4. Dicloxacillin

#Used when theorganism producesB-Lactamase

#Only nafcillin is notacid-resistant

-Examples:ampicillin andamoxicillin (amoxicillin isbetter, absorbedthrough the gut)-Used only to treaturinary tract,sinusitis, lowerrespiratory tract,otitis mediainfections inpneumococcitreatment

-Examples:1. Carbinicillin (notused anymore due tohigh toxicity)2. Ticarcillin (useddue to lower dose)

Pharmacokinetic -Rapidly hydrolysed bygastic acid, so it is notgiven orally but onlyparenterally-Rapidly excreted by renaltubules due to activesecretion of benzylpenicillin in urine(encountered by highdose/depot/simultaneousadministration)-Penetrates less in CSF

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and serous membranes butinfected serousmembranes become morepermeable-Penetrates meningitiswell

-High concentration inbile and can penetrateplacenta to reach thefoetus

Disadvantage -Short duration of action-Unstable in acid-Destroyed by Blactamase-Narrow spectrum

-Indicated on in minorinfections because of:1. Low bioavailability2. High dose frequent3. Narrow spectrum4. B-Lactamasesensitivity

#Cannot be used fortreating bacteraemiabecause of lethal highdose needed

Therapeutic uses:

1. Meningitis2. Pneumococci3. Staphylococcal & streptococcal4. Porphylaxis5. Pneumonia6. Syphilis7. Throat infection

Side Effects:

1. Hypersensitivity depends on the severity2. Anaphylaxis shock

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Protein synthesis inhibitor

Class Aminoglycoside Macrolides Clindamycin Chloramphenicol TetracyclinesElement/

Characteristics*Streptomycin*Gentamicin*Neomycin*Amikacin*Tobramycin*Kanamycin

*Eryhtromycin-Prototype-Has spectrum similar withpenicillin (narrow)-Effective against gram+veorganisms*Clarithromycin*Azithromycin*Telithromycin

-Has similar spectrum toerythromycin-More active againstanaerobes

-Bacteriostatic-Broad spectrum-Active against both gram-ve and gram+ve, aerobesand anaerobes-Active against ricketsiaebut not Chlamydia

-Active against +ve and ve gram organisms

Pharmacokinetic -Poorly absorbed throughoral (except neomycin)-Must be given parenterally-Plasma binding protein isvery low exceptstreptomycin (low serum

level)-Concentration in CSF isinadequate even when themeninges are inflamed (30%of plasma level)-Excreted unchangedthrough kidney-Excretion very much inkidney failure

Erythromycin-Unstable in acid medium-Given through orally(estolate ester) which isresistant to acid orparenterally

-Food interferes withabsorption-Widely distributedthroughout the body fluidexcept CSF-Unique characteristicaccumulation in macrophages-May traverse throughplacenta and reach to foetus-Metabolized in liver, excretedin bile and lost in faeces (noneed for kidney failureadjustment)

-Widely distributed exceptCSF-Penetrate the bones evenwithout inflamed-Metabolized in liver-Excreted in bile

-Rapidly absorbed throughoral-High concentration in CSF-Inactivated by liver byconjugation withglucoronic acid

-Eliminated by non-renalmechanism

Adverse Effect Ototoxicity (irreversible)-Auditory division(neomycin, kanamycin,amikacin)-Vestibular division(streptomycin, gentamicin,tobramycin)

ErythromycinGIT effects-Vomitting, nausea, diarrheadue to stimulating of erythromycin to gastricmotility

-Hypersensitive-Diarrhea and fatalpseudomembranous colitisdue to overgrowth of clostridium difficile (inhibitabsorption of water) and betreated by vancomycin or

-Bone marrow depression-Toxicity of newborn-GIT disturbance-Drug interaction (inhibitother drugs metabolisms)

-GIT disturbance andovergrowth of resistantorganisms-Superinfection withCandida albiicans-Deposition in the bone-Liver toxicity

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