broad spectrum antibiotics


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ANTIBIOTICS By, Guru raj 3 rd BDS


Antibiotic/Antimicrobial Antibiotic : Chemical produced by a microorganism that kills or inhibits the growth of another microorganism Antimicrobial agent : Chemical that kills or inhibits the growth of microorganisms

Microbial Sources of Antibiotics:

Microbial Sources of Antibiotics

Antibiotic Spectrum of Activity:

Antibiotic Spectrum of Activity No antibiotic is effective against all microbes

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Broad spectrum antibiotics - Amoxicillin -Levofloxacin -Gatifloxacillin -Streptomycin -Tetracycline -Chloramphenicol

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INTRODUCTION: A chemical substance produced by a microorganism, which has the capacity to inhibit the growth of or to kill other microorganisms is called as an antibiotic. An antibiotic that is effective against a wide range of infectious microorganisms which includes both gram positive and gram negative bacteria is called as a Broad spectrum antibiotic

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USES OF BROAD SPECTRUM ANTIBIOTICS : Broad-spectrum antibiotics are properly used in the following medical situations: Empirically prior to identifying the causative bacteria when there is a wide differential and potentially serious illness would result in delay of treatment. This occurs, for example, in meningitis, where the patient can become so ill that he/she could die within hours if broad-spectrum antibiotics are not initiated. For drug resistant bacteria that do not respond to other, more narrow spectrum antibiotics In super-infections where there are multiple types of bacteria causing illness, thus warranting either a broad-spectrum antibiotic or combination antibiotic therapy.

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ADVANTAGES OF BROAD SPECTRUM ANTIBIOTICS : . Broader Spectra of Activity .A clear advantage to the use of broad-spectrum antibiotics is that there is less of a need (as compared with narrow-spectrum antibiotics) to identify the infecting pathogen with real certainty before commencing treatment. DISADVANTAGES OF BROAD SPECTRUM ANTIBIOTICS : .Children who receive broad-spectrum antibiotics during their first year of life are at increased risk of developing childhood asthma. .Broad Spectrum antibiotics may give rise to drug resistance.

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TETRACYCLINES Tetracycline antibiotics are protein synthesis inhibitors , inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation complex. Tetracyclines are a group of broad-spectrum antibiotics whose general usefulness has been reduced with the onset of bacterial resistance. Despite this, they remain the treatment of choice for some specific indications. They are so named for their four (“tetra-”) hydrocarbon rings (“-cycl-”) derivation (“-ine”). To be specific, they are defined as "a subclass of polyketides having an octahydrotetracene-2-carboxamide skeleton". [1] They are collectively known as "derivatives of polycyclic naphthacene carboxamide


Tetracyclines are generally used in the treatment of infections of the respiratory tract, sinuses, middle ear, urinary tract, and intestines, and is used in the treatment of gonorrhoea , especially in patients allergic to β- lactams and macrolides ; however, their use for these indications is less popular than it once was due to widespread resistance development in the causative organisms. Their most common current use is in the treatment of moderately severe acne and rosacea ( tetracycline , oxytetracycline , doxycycline , or minocycline ). [ Doxycycline is also used as a prophylactic treatment for infection by Bacillus anthracis ( anthrax ) and is effective against Yersinia pestis , the infectious agent of bubonic plague . It is also used for malaria treatment and prophylaxis, as well as treating elephantiasis . INDICATIONS


CAUTIONS -Children receiving tetracyclines and babies born to women treated with these agents from midpregnancy on may develop brown discoloration of the teeth and possibly affect the growth of teeth and bones. -Increased intracranial pressure may result from the use of tetracyclines in young babies. -These drugs must be given with great care to any patient with impaired kidney and liver function. -Tetracyclines may increase muscle weakness in myasthenia gravis and worsen systemic lupus. .

Interactions Tetracyclines may interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes tetracyclines should let a physician know all other medicines he or she is taking:

Interactions Tetracyclines may interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes tetracyclines should let a physician know all other medicines he or she is taking - It was believed that tetracycline antibiotic impair the effectiveness of many types of hormonal contraception. -Tetracycline may result in excessive "thinning" of the blood. Exaggerated sunburn can occur with tetracyclines; therefore, sunlight should be minimized during treatment

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Among the drugs that may interact with tetracyclines are: -antacids -calcium supplements -medicines that contain iron (including multivitamin and mineral supplements) -laxatives that contain magnesium -cholesterol-lowering drugs such as cholestyramine ( Questran ) and colestipol ( Colestid ) - salicylates such as Magan and Trilisate - penicillins -birth control pills


Side-effects Side-effects from tetracyclines are not always common, but of particular note is possible photosensitive allergic reaction that increases the risk of sunburn under exposure to UV light from the sun or other sources. This may be of particular importance for those intending to take on vacations long-term doxycyline as a malaria prophylaxis. They may cause stomach or bowel upsets, and, on rarely occasions, allergic reactions. Very rarely, severe headache and vision problems may be signs of dangerous secondary intracranial hypertension , also known as pseudotumor cerebri . Tetracyclines are teratogens due to the likelihood of causing teeth discolouration in the fetus as they develop in infancy. For this same reason, tetracyclines are contraindicated for use in children under 8 years of age. They are, however, safe to use in the first 18 weeks of pregnancy. Some patients taking tetracyclines require medical supervision because they can cause steatosis and hepatotoxicity


CLASSIFICATION Naturally-occurring Tetracycline Chlortetracycline Oxytetracycline Demeclocycline Semi-synthetic Doxycycline Lymecycline Meclocycline Methacycline Minocycline Rolitetracycline According to source

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According to duration of action: Short-acting (Half-life is 6-8 hrs) Tetracycline Chlortetracycline Oxytetracycline Intermediate-acting (Half-life is ~12 hrs) Demeclocycline Methacycline Long-acting (Half-life is 16 hrs or more) Doxycycline Minocycline Tigecycline

Administration :

Administration -When ingested, it is usually recommended that the more water-soluble, short-acting tetracyclines (plain tetracycline, chlortetracycline, Oxytetracycline, demeclocycline and methacycline) be taken with a full glass of water, either two hours after eating, or two hours before eating. - This is partly because most tetracyclines bind with food and also easily with magnesium , aluminium , iron , and calcium , which reduces their ability to be completely absorbed by the body. -Dairy products, antacids, or preparations containing iron are particularly recommended to be avoided near the time of taking the drug. . [11]

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Partial exceptions to these rules occur for doxycycline and minocycline, which may be taken with food (though not iron, antacids, or calcium supplements). Minocycline , can be taken with dairy products because it does not chelate calcium as readily, although dairy products do decrease absorption of minocycline slightly For most infections, tetracycline is taken two to four times daily for 7 to 14 days. Preparation : Capsules: 250mg, 500mg; Tablets: 250mg, 500mg; Syrup: 125 mg/teaspoon. Storage: Capsules should be kept below 30°C (86°F).


CHLORAMPHENICOL Mechanism of action Inhibits protein synthesis ( 50 s subunit ) Antibacterial activity H. Influenzae S. typhi N. Meningitidis E. coli S. Pneumoniae V.cholera Ricketsiae Anaerobes- clostridium & B. fragilis

Chloramphenicol ( cont. ):

Chloramphenicol ( cont. ) Pharmacokinetics Rapidly & completely absorbed from GIT 30 % protein bound Metabolized by liver – glucuronidation Well distributed, including CNS and CSF Excreted in urine

Chloramphenicol Cont. ):

Chloramphenicol Cont. ) Clinical uses Limited because of potential toxicities (a plastic anaemia &circulatory collapse in neonates ) 1. Typhoid fever- s. typhi ( quinolones are preffered) 2. Meningitis – H.influenzae,N.meningitidis,S.pneumoniae ( Ceftriaxone is preffered ) 3. Anaerobic infections- B. fragilis (Metronidazole is the drug of choice) 4. Rickettsial infections – Doxycycline is preffered 5. Bacterial conjunctivitis ( topical )

Chloramphenicol ( cont. ):

Chloramphenicol ( cont. ) Side effects 1.Hypersensitivity- low incidence May ppt hemolysis in G6PD deficient pts 2. A plastic anaemia ( fatal ) 3.Grey baby syndrome 4.Suprainfections 5. Interaction with other drugs : Inhibits liver microsomal enzymes Phenytoin Tolbutamide Chlorpropamide Anticoagulants