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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
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.
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
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.
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% .
.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.
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
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
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
.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.
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.
Mode of action Bacteriostatic and bacteriocidal Anti-bacterial against organism mainly their growth phase Interferes with synthesis of ribonucleic acid
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
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
. 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
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
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
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
Properties Colourless solid Dissolves in water but soluble in organic solvents Optically active and Leavoratotary Basic in nature
StructureStreptomycin is made up of three basic units: Streptidine L-streptose N- methyl L- glucosamine
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
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
Properties Reddish brown crystalline powder Slightly soluble in water, completely in methanol It exist as a “zwitter ion”
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
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
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.
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.
MODE OF ACTION It is rapidly absorbed orally but food delays absorption high tissue penetrability concentration in lung muscle and boneExcreted 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.
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 &AIDSActivity include gram +tve cocci and enterobacteriaceaeIt cause seizuse at higher doses.