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All the following are antibiotics used for gram –ve bacteria.

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Presentation on theme: "All the following are antibiotics used for gram –ve bacteria."— Presentation transcript:

1 All the following are antibiotics used for gram –ve bacteria

2 Aminoglycosides 1- Streptomycin 2- Kanamycin 3- Tobramycin 4- Amikacin 5- Neomycin 6- Gentamicin Protein synthesis inhibitor N,.B. 1,3,&6 most commonly used neomycin is only used topically because it is highly nephrotoxic

3 Cont’d Antibacterial Spectrum: 1. Bactericidal, exclusive for aerobic G-ve bacteria 2. M.tuberculosis, streptomycin & amikacin, only for the first 2 weeks due to its side effect Why are aminoglycosides considered ineffective against anaerobes?? Because aminoglycosides are transported across the bacterial cell membrane by active transportation which is an oxygen-dependent process.

4 Cont’d Pharmacokinetics: 1. Polycations (highly charged) 2. Poorly absorbed by the GIT (parenteral or topical) 3. Low distribution to most cells, including CNS 4. Only 10 % of the drug binds to plasma proteins 5. No significant metabolic breakdown, excreted unchanged in urine (glomerular filtration) 6. Half-life is: 2-3 hours

5 Cont’d Mechanism of action: 1. Inhibition of protein synthesis by irreversibly binding to the 30S ribosomal subunit 2. Bactericidal 3. Inhibition of cell wall synthesis increases their entrance into cells (synergism) e.g. Piperacillin or ceftazidime + gentamycin or tobramycin against P. aeruginosae

6 Clinical uses: 1. T.B. (streptomycin & amikacin IM) 2. P. aeruginosa infections (other than UTI) an aminoglycoside+ piperacillin or an aminoglycoside+ ceftazidime (P. aeruginosa causing UTI, ciprofloxacin is preferred) 3. Brucellosis in combination with tetracycline ( in treating severe cases) 4. Topical: Creams, ointments or solution for infected burns, wounds or skin lesions. Ear & eye drops and ointments

7 Cont’d Adverse Effects 1- Ototoxicity & nephrotoxicity (directly related to serum conc.) 2- Neuromuscular blockade (in very high doses, Curare-like action) Special problems with aminoglycosides : Narrow therapeutic index Monitoring of serum levels. because more than 90% of the drug is free in the plasma

8 SPECTINOMYCIN Antibacterial spectrum: Mainly effective against N. gonorrhea Pharmacokinetics: Taken IM only Does not penetrate the BBB It is excreted by glomerular filtration Mechanism of action Similar to aminoglycosides, inhibits protein synthesis by binding to the 30S ribosomal subunit.

9 Cont’d Clinical uses 1. Used only as an alternative agent for infections caused by N. gonorrhea in patients who cannot tolerate ceftriaxone or quinolones. Adverse effects: 1. Pain at the site of injection 2. Rash, headache, dizziness, vomiting & nervousness 3. Nephrotoxicity & anemia are rarely observed

10 In case of N. gonorrhoea infection first- line of drugs is: 1. Cephalosporins ولو مانفعشي 2. Ciprofloxacin ولومانفعشي 3. Spectinomycin

11 POLYMIXIN Polymixin B, Polymixin E Polymixin B is the most important Mechanism of action: 1. Interaction with phospholipids of the cell membrane disrupting its structure Antibacterial spectrum 1. Selective against G –ve bacilli, esp. pseudomonads. 2. Inactive against G +ve bacteria. Clinical use 1. Not used systemically B/C it is highly nephrotoxic. 2. Topically used with neomycin or bacitracin for ear, eye or skin infections due to pseudomonads & other G-ve bacteria.

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