Antibiotics

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Antibiotics

  1. 1. Antibiotics Antibiotics are the chemical substances obtained from various micro organisms First discovered antibiotic is Penicillin by Alaxander Flemming in 1940 Antibiotics are used to cure diseases caused by bacteria such as pneumonia, tuberculosis, meningitiesConditions for a substance to act as antibiotics are as follows: Should be effective at low concentration Should not have toxic side effects Must be effective against pathogens Should be stored for a long time without appreciable loss of its activity Should be highly stable so that it can be isolated easily and absorbed readily Should be available at low cost Should be completely eliminated from the body after its administration has been stopped
  2. 2. Classification of antibioticsClassification based on chemical structure: Cyclic structure– cyclopentane , cyclohexane and clycloheptane derivatives Tetracycline antibiotics - tetracycline Aromatic antibiotics - Chloramphenicol Amino Glycoside antibiotics - streptomycin Macrolides antibiotics – Erythromycin.
  3. 3. Chloramphenicol Discovered by Ehrlich in 1947 Obtained by culture of “Streptomyces Venezuelae”Properties Stable neutral compounds Bitter in taste Sharp melting point Soluble in organic solvents and sparingly soluble in water Optically active Molecular formula C H O N Cl 11 12 5 2 2 On hydrolysis it gives dichloro acetic acid & optically active base On reduction with Sn/ HCl followed by diazotization & coupling with β-naphthol – orange red dye On acetylation in pyridine–shows the presence of two OH groups
  4. 4. Therapeutic uses Effective against gram +ive and gram –ive bacteria It’s the first broad spectrum antibiotic Inhibits the growth of stephalococcus, streptococcus bacillus Used in treatment of typhoid, pneumonia, ricketisia, urinary tract infection, whooping cough, meningitis, plague, syphilis, gonorrhea & dysentry Employed in acute infections due to Haemophilus influenza Can be used in the treatment of skin and eye infection It is absorbed in a intestinal tract and diffused into tissues. As it is insoluble in water it has to be administered in the form of fine particles.
  5. 5. Structure, activity, relationship of ChloramphenicolModification of para nitro phenyl group: If the nitro group of phenyl ring of chloramphenicol is replaced by other substituents like CN , their physiological activity is reduced Shifting the nitro group from para position , reduces the anti-bacterial activity If phenyl ring of choloramphenicol is replaced by alicyclic or hetrocyclic ring, then the resulting antibiotic is found to be less effectiveModification of Dichloroacetamide chain If chloro group is replaced by bromo group , the antibacterial activity is only 80% .
  6. 6. .Modification of 1,3 propane diol The propane diol group is essential for its antibacterial activity If the length of the propane is altered, the drug is deactivated If the bulkier substituents are introduced activity is decreasedSTEREOCHEMISTRY: cholramphenol has two asymmetrical carbon atom. It can form 4 optically active isomers-D & L threo isomers and D & L erythro isomers. Erythro isomers- toxic & not used in medicine L-threo isomer-biologically inactive. D-threo isomer – biologically active.
  7. 7. Toxicity Nitro group may contribute to bone marrow depression and Fatal blood dyscrasiaDosage Adult dosage- 500mg every 6 hrsMODE OF ACTION It inhibits the growth of bacteria.DOSAGE FORMS available as: capsules, ear drops, eye ointment
  8. 8. Penicillin Widely used antibiotic Extracted from mould of “Penicillin notatum” Belongs to a group of antibiotic called β-lactam Antibiotic Basic structure contains thiozoline ring fused with β-lactam ring Two rings constitute the fundamental nucleus of group of antibiotics referred as “PENICILLIN” Chrysogunum- highest yield of penicillin
  9. 9. Therapeutic uses Penicillin is effective against gram +ive and gram –ive coccai and some gram +ive bacilli It is bacteriostatic in action, but at certain concentration it acts as bactericidal agents. Inhibits synthesis of bacterial cell wall Non-toxic even in large doses. Effective against pneumocccal infections, streptococcal infections, staphylococcal infections, meningococcal infections. Used in the treatment of diphtheria, gangrene, tetanus, etc Used topically, orally or parentally In oral therapy, the dosage must be given in larger doses as it is inactivated by gastric acids Sodium or potassium salt are used for injection Calcium salt can be used as an ointment or as powder
  10. 10. .Adverse effects adverse effects like vomiting, nausea, anyphyxis and allergic reactions Natural penicillin are inactivated faster by HCL acids, variety of semi synthetic and synthetic penicillin are produced that are made effective All these have allergic reactions similar to those produced by natural penicillin.
  11. 11. Types of penicillin &PropertiesTypes of penicillin Natural penicillin Semi synthetic penicillinProperties Optically active Soluble in water Hydrolyzed by hot inorganic acids Acid resistant Effective in treatment of respiratory tract infection, streptococcal infections and pneumonococcal infections Methicillin is resistant to penicillinase and used in treatment of infection resistant to benzyl penicillin Ampicillin is effective against influenza, gonorrhea, salmonella typhose, e- coli, etc.
  12. 12. Mode of action Bacteriostatic and bacteriocidal Anti-bacterial against organism mainly their growth phase Interferes with synthesis of ribonucleic acid
  13. 13. TetracyclinsTetracyclins compress a group namely: Tetracyclins Chlorotetracyclins Oxytertacyclins Most important anti-microbial property Obtained from the species of actinomyces named as streptomyces Precipitated from a culture medium maintained at a pH 8-10 in presence of divalent cations Can be separated by ion exchange chromatography
  14. 14. Therapeutic uses Effective against gram+ive and gram –ive micro-organisms Bacteriostatic Inhibit essential enzymes in bacterial cell Prevent synthesis of ribosomes Used in treatment of infections such as pneumonia, actinomycosis, urinary infection, spotted fever, typhus fever, gonorrhea, syphilis,plague, ricketisia, etc. Oromycin is effective against many bacteria similar to cholorominphenicol but is not as effective as chloramphenicol against typhoid fever
  15. 15. . Less toxic drug, tolerated by patients Tetramycin is more stable than oramycin Used in treatment of conjunctivitis, cholera, amoebic dysentery, etc. Its effective against pneumonococci, streptococci, H- influenza, e-coli, M-tuberculosis Absorbed in duodenum and small intestine Long duration of anti-bacterial action They form insoluble complexes with calcium and magnesium Substances like milk which contain calcium and antacids reduce their absorption Not advisable for children and pregnant women
  16. 16. Chemical properties Yellow, odourless, crystalline powder with bitter taste Sparingly soluble in water Oxidized by oxygen in air, they darken when exposed to air Amphoteric in nature , basicity is due to N-amino group and acidity is due to phenolic group Form chelates with metal ions Due to the presence of phenol, it gives colour with neutral ferric chloride and forms azo dye Gives florescence in presence of UV light
  17. 17. Streptomycin Belongs to the important amino glycosidic group of antibiotic It is given the name from streptomyces Organism producing the antibiotic is known as “Streptomyces Griseus” Other examples of amino glycosidic antibiotics are gentamycins, neomycins
  18. 18. Therapeutic uses Used in treatment of tuberculosis, infections of e-coli, H- influenza, plague, respiratory tract infection, meningities Bactericidal properties Disturbs the normal protein synthesis and bacteria Destroyes the cell membrane
  19. 19. Properties Colourless solid Dissolves in water but soluble in organic solvents Optically active and Leavoratotary Basic in nature
  20. 20. StructureStreptomycin is made up of three basic units: Streptidine L-streptose N- methyl L- glucosamine
  21. 21. Rifamycin It is isolated from “Streptomyces mediterranei” Belongs to a new class of antibiotics called “Ansamycins” There are five types of rifamycis A,B,C,D,E Cant be administered orally Given intravenously
  22. 22. Therapeutic uses Inhibits the growth of gram +ive bacteria such as e-coli, keri bacila Effective against staphylococcus Acts by blocking the biosynthesis of nucleic acid of bacteria Used in the treatment of tuberculosis
  23. 23. Properties Reddish brown crystalline powder Slightly soluble in water, completely in methanol It exist as a “zwitter ion”
  24. 24. Cephalosporins Isolated from the fungi “Cephalosporium acremonium” in 1948 They are β-lactum antibiotic with same fundamental structure as penicillin It contains dihydro-meta thiazine ring Most acid stable than penicillinClassification of cephalosporin Cephalosporin N Cephalosporin P Cephalosporin CCephalosporin C is true cephalosporin
  25. 25. Therapeutic uses Used in the treatment of urinary tract infections, streptococcal infections, pneumonia, tonsillitis, skin infections, etc. Inhibits cross linking of peptide units in bacterial cell wall
  26. 26. CIPROFLOXACIN They have been divided into four generations This division is chronological order, the overall antibacterialspectrum as well as potency. It is the most potent first generation fluoroquinolones activeagainst broad range of bacteria-aerobic gram -tve bacilli & gram+tve bacteria at higher concentrations. important feature- tissue penetrability.
  27. 27. THERAPEUTIC USES Effective against urinary tract infections,typhoid,bone,soft tissuegynaecological and wound infections,respiratory infections,tuberculosis, meningitis and conjunctivitis First choice drug- typhoid cells since chloramphenicol,amphicillil and cotrimaxazole are unreliable due to developmentof resistance. Used as a component of combination of multi drug treatment oftuberculosis and respiratory infections.
  28. 28. MODE OF ACTION It is rapidly absorbed orally but food delays absorption high tissue penetrability concentration in lung muscle and boneExcreted by urineADVERSE EFFECTS Produces nausea, vomiting and bad taste Cause head aches, anxiety & insomnia,some times rashes onthe skin. not admistered to children- damage to weight bearing joints.
  29. 29. CARBAPENEMS Extremely potent and broad spectrum antibiotic. It is a β-lactone antibiotic resistant to β-lactinases. limiting feature of imipenim is rapid hydrolysis by enzymepeptidase located in the border of renal tubular cells. effective in treatment of hospital acquired infections- cancer &AIDSActivity include gram +tve cocci and enterobacteriaceaeIt cause seizuse at higher doses.

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