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Antibiotics- types based on mechanism of action

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Antibiotics- types based on mechanism of action

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Inhibit cell wall synthesis- beta lactams.

Natural penicillins
 Penicillin G Penicillin V Benzathine P Procaine P, Penicilllinase R
 Methicillin Nafcillin Cloxacillin Dicloxacillin Oxacillin , Amoxicillin Ampicillin ,Antipseudomonal penicillins
 Ticarcillin Pipercallin
also comes in combination with Tazobactam 
( Tazocin ) Carbeniclin

Cephalosporins – 1st Gen
 Cefadroxil Cephalexin Cephradine Cefazolin 2nd Gen Cefaclor Cefamandole Cefuroxime Cefoxitin 3 rd generation -Cefdinir Cefditoren Cefotaxime Cefpodoxime Ceftibuten Cefsulodin 
 Cefotaxime Ceftazidime Ceftriaxone Cefixime Cefoperazone Ceftizoxime Cefteram
,4th Gen

 Cefepime
Cefpirome
Cefozopran ,5th Gen Ceftaroline Ceftobiprole

. Similar to penicillin ( structure and mode of action ) Broader spectrum with each successive generation Limited activity against anaerobes Renal excretion About 0.5 to 6.5 % of penicillin sensitive patients will also 
be allergic to cephalosporins .Orally active 1st and 2nd gen cephalosporins have a similar antimicrobial activity Cefixime is an orally active 3rd gen CS Ceftriazxone – long 1/2 life and can be given once daily

Carbapenems –found in 1976 very broad spectrum resistant to B lactamases ( resist the hydrolytic action of beta-lactamase enzyme often considered antibiotics of last resort. Impipenem Meropenem Ertapenem Doripenem Impipenem + 
Cilastatin

Monobactams -Aztreonam –only commercially available monobactam narrow spectrum only active against Neisseria and Pseudomonas No effective against Gr +ve or anaerobes No cross reaction in Beta lactam allergy

Glycopeptides- composed of glycosylated cyclic or polycyclic nonribosomal peptides Vancomycin and teicoplanin work against almost all types of Gram +ve organisms including MRSA Vancomycin also indicated in pseudomembranous colitis caused by Clostridium difficile Both can cause two types of hypersensitivity reactions- Red man syndrome and anaphylaxis.Vancomycin Teicoplanin Telavancim Bleomycin

Beta-lactamase inhibitors – Clauvanic acid , sulbactam, tazobactam Combinations – Amoxicillin / clavulanic acid , Imipenem/ cilastatin , Ampicillin / sulbactam Polymixins – polymixin B and E Others – colistin , daptomycin , gramicidin , isoniazid

Inhibit protein synthesis. tetracyclines-Grouped historically into different generations based on the method of synthesis
○ Biosynthesis- 1st generation eg tetracycline , chlortetracycline, Oxytetracycline and Demeclocycline
○ Semi-synthesis 2nd generation eg Doxycyline , Lymecycline , Meclocyline and Roolitetracycline
○ Total synthesis- 3rd generation eg Tigecyline They interact with the 30 s subunit of the bacterial ribosome and prevent binding by tRNA molecules blocking protein synthesis Active against a wide range of microorganisms including gram negative bacteria , chlamydiae , mycoplasmas , rickettsiae and protozoan parasites Can cause teeth discoloration in children ( avoid in children and pregnant women ) Tetracylcine Oxytetracylcine Demeclocycline Minocycline Doxycyline Lymecycline Meclocycline Methacycline Rolitetracycline Tigecycline

aminoglycosides-3-amino sugars Broad spectrum ( Gr -ve aerobes , Gr +ve aerobes ) Streptomycin has been used to treat bubonic plague , tularemia and tuberculosis ( but was highly toxic ) Used widely for infections caused by Gr -ve rods Tobramycin used to treat Pseudomonas infection in patients with cystic fibrosis Beware risk nephrotoxicity , ototoxicity and neuromuscular paralysis 
( with rapid IV infusion ) Streptomycin Neomycin Gentamicin Amikacin Tobramycin Kanamycin Netilmicin

Macrolides- Wider spectrum than pencillin Inhibit bacterial RNA-dependent protein synthesis Often used in patients who are allergic to penicillin Active against a broad variety of bacteria : some Gr +ves , Gr -ves , atypicals , some mycobacteria and spirochaetes Excellent tissue and cellular penetration Up to a 3rd can get GI side effects ( ↑ with erythromycin ) like nausea , vomiting, diarrhoea and dyspepsia Erythromycin Clarithromycin Azithromycin Roxithromycin Spiramycin Tylosin Telithromycin

Lincosamides include Clindamycin and Lincomycin
○ exhibit biological activity against Gr +ve bacteria and protozoans
○ Clindamycin used widely in treatment of bacterial infections caused by anaerobic species and protozoal disease e.g. malaria combination with other antibiotic or non-antibiotic antimicrobials ( primaquine, fosfidomycin, benzoyl peroxide ) Linezolid – oxazolidinone antibacterial works against Gr +ve bacteria including MRSA and glycopeptide-resistant enterococci
Not active against common Gr -ve organisms – used in combination for mixed infections that also involve Gr -ve organisms ( used in surgical infections ) Fusidic acid- narrow spectrum used to treat Staphylococcus aureus. It also has an unusual spectrum of activity that includes cornybacteria , nocardia, anerobes and Neisseria species

Nucleic acid inhibitors –Flumequine Nalidixic acid Oxolinic acid Pipemidic acid

Fluoroquinolones-Ciprofloxacin Ofloxacin Norfloxacin Perfloxacin Levofloxacin Sparfloxacin Moxifloxacin Gatifloxacin Difloxacin Enrofloxacin Marbofloxacin

Anaerobic DNA inhibitors-Nitro-imidazole derivative Metronidazole Metronidazole is an antiprotozoal and antibacterial agent effective against Trichomonas vaginalis and other protozoa + anaerobes. Nitrofuran derivative-Nitrofurantoin Furazolidone.Rifampicin

References Antibiotics : Classification and mechanisms of action with emphasis on molecular perspectives International Journal of Applied Microbiology and Biotechnology research IJAMBR 4 ( 2016 ) 90-101 Boundless Microbiology- Functions of Antimicrobial Drugs Glycopeptide antibiotics- via https://www.sciencedirect.com/topics/neuroscience/glycopeptide-antibiotic Antibiotic classification and mechanism via www.orthobullets.com Lincosamides : Chemical structure , biosynthesis , mechanism of action , resistance and applications Biochem Pharmacol. 2017 Jun 1;133:20-28 British National Formulary via – www.bnf.org www.Toku-e.com antibiotic classification and general information Medicine compendium www.medicines.org.uk

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