1. Welcome

2. Overview of Aminoglycosides and other protein synthesis inhibitors

3. Presented By Maruf Kamal (2008-3-70-006) Sabbir Ahmed (2008-3-70-007)
Md. Tanvir Rahman ( )

4. Introducton:
An aminoglycoside is a molecule or a portion of a molecule composed of amino-modified sugars.
Several aminoglycosides function as antibiotics that are effective against certain types of bacteria. They include amikacin, arbekacin, gentamicin, kanamycin, neomycin, netilmicin, paromomycin, rhodostreptomycin, streptomycin, tobramycin, and apramycin.

5. History: Aminoglycoside Year Source organism streptomycin 1944
Aminoglycoside
Year
Source organism
streptomycin
1944
Streptomyces griseus
neomycin
1949
Streptomyces fradiae
kanamycin
1957
Streptomyces kanamyceticus
paromomycin
1959
Streptomyces rimosus
spectinomycin
1962
Streptomyces spectabilis
gentamicin
1963
Micromonospora purpurea
tobramycin
1968
Streptomyces tenebrarius
sisomicin
1972
Micromonospora inyoensis
amikacin
semisynthetic derivative of kanamycin
netilmicin
1975
semisynthetic derivative of sisomicin

6. History:
The first aminoglycoside, streptomycin, was isolated from Streptomyces griseus in Neomycin, isolated from Streptomyces fradiae, had better activity than streptomycin against aerobic gram-negative bacilli but, because of its formidable toxicity, could not safely be used systemically. Gentamicin, isolated from Micromonospora in 1963, was a breakthrough in the treatment of gram-negative bacillary infections, including those caused by Pseudomonas aeruginosa. Other aminoglycosides were subsequently developed, including amikacin (Amikin), netilmicin (Netromycin) and tobramycin (Nebcin), which are all currently available for systemic use

7. Nomenclature
Aminoglycosides that are derived from bacteria of the Streptomyces genus are named with the suffix -mycin, whereas those that are derived from Micromonospora are named with the suffix -micin.
This nomenclature system is not specific for aminoglycosides. For example, vancomycin is a glycopeptide antibiotic and erythromycin, which is produced from the species Saccharopolyspora erythraea (previously misclassified as Streptomyces) along with its synthetic derivatives clarithromycin and azithromycin, is a macrolide. All differ in their mechanisms of action, however.

8. Physical and chemical properties:
They are water-soluble due to their polar groups (hydroxyl and amine groups), stable in solution and more active at alkaline than at acid PH.
Aminoglycosides frequently exhibit synergism with β-lactams or vancomycin.
However, aminoglycosides may complex with β- lactam drugs, resulting in loss of activity and they should not be mixed together for administration.

9. Specific Agents Amikacin (Amikin®), Gentamicin (Garamycin®),
Kanamycin (Kantrex®),
Neomycin, Netilmicin (Netromycin®),
Streptomycin, Tobramycin (Nebcin®)

10. Structure of Aminoglycosides

11. Mechanism of action
bactericidal; aminoglycosides bind to the 30S subunit of the bacterial ribosome, interfering with the binding of fMet-tRNA and therefore the formation of the initiation complex. Binding to the 30S subunit may also cause misreading of mRNA codons
β-lactams, vancomycin facilitate uptake by Gram- positive organisms
resistance: via plasmid-mediated aminoglycoside- modifying enzymes

12. Mechanism of action

13. Pharmacokinetics poor oral absorption
volume of distribution approximates the extracellular space (about 0.26 L/kg)
(larger in cystic fibrosis patients, about 0.35 L/kg)
tissue distribution variable (poor CNS penetration)
negligible metabolism
renally eliminated (filtered, with a small amount of proximal reabsorption)
elimination half-life: 2-3 hours (if renal function normal)

14. Pharmacodynamics concentration-dependent killing
postantibiotic effect (concentration-dependent)

15. SARs of Aminoglycosides
Crucial for broad spectrum activity
Primary target for inactivating enzymes
Congeners with amino groups at 2' and 6' are especially active

16. SARs of Aminoglycosides
Methylation of these amines does not alter activity,decreases inactivation
Hydroxyls at the 3' or 4‘ position are not critically important

17. SARs of Aminoglycosides
Modifications compromise antibacterial activity
One exception is amikacin with its aminohydroxybutyrate

18. SARs of Aminoglycosides
Substitution pattern is somewhat more flexible
Only real requirement is the amine at the 3" position.

19. Spectrum of activity
Aminoglycosides are classified as broad-spectrum antibiotics, they used for treatment of serious systemic infections caused by
Aerobic Gm –ve bacilli.
Aerobic Gm –ve and Gm +ve cocci (with the exception of Staphylococci) tend to be less sensitive to aminoglycosides and thus the β-lactam and other antibiotics tend to be preferred for the treatment of infections caused by these organisms.

20. Spectrum of activity
broad gram-negative spectrum including P. aeruginosa
gram-positive: synergistic in combination with ß- lactams, glycopeptides
anaerobes: negligible activity
amikacin: Nocardia, MAI, certain rapid-growing mycobacteria, gentamicin-resistant gram-negative bacilli
streptomycin: multidrug-resistant tuberculosis, tularemia, plague

21. Adverse reactions nephrotoxicity
proximal acute tubular necrosis (ATN) → ↓ GFR
likely related to inhibition of intracellular phospholipases in the proximal tubule
tends to be reversible
associated factors: hypotension, dehydration, duration of therapy, concomitant liver disease, advanced age, other nephrotoxins (vancomycin)
nephrotoxicity correlates with drug accumulation in the renal cortex

22. Aminoglycoside accumulation in critically ill surgical patients

23. Toxicity 1- Nephrotoxicity 2- Ototoxicity 3- Neurotoxicity
4- Neuromuscular blockade
Additional adverse reactions with administration of aminoglycosides may include: nausea, vomiting, anorexia, rash, and urticaria.

24. Toxicity ototoxicity vestibulotoxic and cochleotoxic
generally irreversible
difficult to assess
high tone frequencies affected first
neuromuscular blockade
rare but potentially serious
enhanced by conditions or drugs affecting the NM junction (e.g., myasthenia gravis, succinylcholine)
can be treated with calcium

25. Contraindications:
Aminoglycosides should not be given to patients requiring long term therapy because of the potential for ototoxicity and nephrotoxicity.
These drugs are contraindicated in patients with:
- Preexisting hearing loss Myasthenia gravis
- Parkinsonism
- During lactation or pregnancy.
The aminoglycosides are used cautiously in patients with renal failure, in the elderly and in patients with neuromuscular disorders.

26. Drug interactions:
Administration of aminoglycosides with the cephalosporins may increase the risk of nephrotoxicity.
When the aminoglycosides are administered with loop diuretics there is an increase the risk of ototoxicity (irreversible hearing loss).
There is an increased risk of neuromuscular blockage (paralysis of the respiratory muscles) if the aminoglycosides are given shortly after general anesthetic (neuromuscular junction blockers).

27. Drug interactions:
Increased risk of nephrotoxicity and ototoxicity when aminoglycosides given with vancomycin.
Increased risk of nephrotoxicity when aminoglycosides given with colistin.
Aminoglycosides antagonize effects of neostigmine.

28. Streptomycin sulfate
Neomycin sulfate

29. Kanamycin sulfate
Amikacin

30. Gentamicin sulfate
Netilmicin sulfate

31. Other Protein Synthesis Inhibitors
Tetracycline
Chloramphenicol
Macrolides
Mupirocin
Quinolones

32. Mechanisms action of tetracycline

33. Commercially available tetracyclines
First generation (Dose intervals shorter)
Chlorotetracycline
Oxytetracycline
Tetracycline
Dmeclocycline
Second Generation (Dose interval longer)
Minocycline
Methacycline
Doxycycline
Third Generation
Glycylcycline

34. Mechanism action of chloramphenicol

35. Structure of cloramphenicol

36. MUPIROCIN
Mupirocin is active against many gram-positive and selected gram-negative bacteria. It has good activity against S. pyogenes and methicillin-susceptible and methicillin-resistant strains of S. aureus. It is bactericidal at concentrations achieved with topical application.
Mupirocin inhibits bacterial protein synthesis by reversible inhibition of Ile tRNA synthase. There is no cross-resistance with other antibiotic classes. Clinically insignificant, low-level resistance results from mutations of the gene encoding Ile tRNA synthase or an extra chromosomal copy of a gene encoding a modified Ile tRNA synthase. High-level resistance is mediated by a plasmid or chromosomal copy of a gene encoding a “bypass” synthetase that binds Mupirocin poorly.

37. Mechanism action of chloramphenicol

38. Structure of chloramphenicol

39. Mode of action of Macrolides

40. Examples of Macrolides
Erythromycin
Clarithromycin
Roxithromycin
Azithromycin

41. Mupirocin is available as a 2% cream or ointment for dermatologic use and as a 2% ointment for intranasal use. The dermatological preparations are indicated for treatment of traumatic skin lesions and impetigo secondarily infected with S. aureus or S. pyogenes. Systemic absorption through intact skin or skin lesions is minimal. Any Mupirocin absorbed is rapidly metabolized to inactive monic acid.
Mupirocin is effective in eradicating S. aureus carriage. The consensus is that patients who may benefit from Mupirocin prophylaxis are those with proven S. aureus nasal colonization plus risk factors for distant infection or a history of skin or soft tissue infections.
Mupirocin may cause irritation and sensitization and contact with the eyes should be avoided.
Systemic reactions to Mupirocin occur rarely, if at all. Application of the ointment to large surface areas should be avoided in patients with renal failure to avoid accumulation of polyethylene glycol from the ointment.

44. Examples of Quinolones
Nalidixic acid
Ciprofloxacin
Levofloxacin
Glatifloxacin
Norfloxacin
Sparfloxacin
Fluroquinolone

45. THANK YOU