Aminoglycosides Flashcards
Chimically?
Chimically aminoglycosides consist of two or more amino sugars joined by aGlycosidic bond to ahexose nuclues usually situated in the center . this hexose is either streptidine or 2 deoxystreptamine
Sourses ?
Natural drugs obtained from different types of bacteria and fungi .
Sourse of streptomycin ?
Sterptomyces griseus
Sourse of Neomycin ?
Sterptomyces fradie
Sourse of Kanamycin ?
Sterptomyces kanamycetieus
Sourse of Gentamycin ?
Microspora
Mechanism of action ?
Aminoglycoside are rapidly bactericidal antibiotics . act by entering into cytoplasm of the bacterial cell where they bind to polysomes and interfer with protein biosynthesis by causing misreading and premature termination of translation of mRNA
Spectrum ?
Is mainly confined to gram negative bacilli
Mention same aminoglycosides ?
Gentamycin Sterptomyces Kanamycin Tobramycin Amikacin
Antimicrobial spectrum ?
Pseudomonas aeruginosa Escheria coli Enterobacter spp Klebsella spp Sderralia spp Proteus mirabilis Enterococcus foecalis Staphllococcus aureus
Pharmacokinetics ?
Aminoglycoside are poorly absorbed by GIT because of their high polarity ( only less than 1% is absorbed ) they are inactivated in the intestine , so the aminoglycoside are administered parentrally where they are rapidly absorbed . with exception of sterptomycin binding of aminoglycoside to plasma protein is negligible , so their distribution in body tissues is very low . they can’t penetrat BBB and should be injected intrathecally to attain effective concentration in CSF. Excretion of aminoglycoside is urinary
Adverse reactions ?
1- Ototoxicity :- adminstration of aminoglycosides results in both vestibular and auditory dysfuntion.this occurs due to accumulationin the perilymph and endolymph of inner ear . ototoxicity is irreversible and is due to destruction of vestibular or Cochlear sensory cells .
2-Nephrotoxicity :- result due to accumulation of aminoglycosides in the proximal tubular cells . Reflected by proteinurea and appearance of granular casts . GFR is reduced after days of beginning treatment . Severe acute necrosis may occur , mild increase in plasma creatinine is detected
3- Neuromuscular blockade:- occur on adminstration of large doses , relatively uncommon .
4- Streptomycin cause Optic dysfunction in form of enlargement of blind spot and peripheral neuritis .
5- Mild adverse effects include : skin rash ,eosinophilia and exfoliative dermatitis
Amikacin ( Amikin )?
Abroad spectrum aminoglycosides. Is resistant to aminoglycosides- inactivating enzyme . Used for bacteria resistant to gentamycin .
Dose of Amikacin ?
15mg/kg body weight (in sigle or divided doses ) for at least 5 days
What is antibactereial spectrum of Neomycin ?
Broad spectrum
What is therapentic uses of neomycin ?
Sensitive infections in skin and mucous membranes ( incombination with erythromycin ) for prepration of bowel for surgeory
Dose of neomycin ?
4-12 grams
The high dose of neomycin is dangerous ?
The high dose is not dangerous because no absorption takes place and the action is local .
ather name of Kanamycin?
Kantrax
Kanamycin ?
Can be administered orally or parentrally . Use of kanamycin is limited because it antibacterial spectrum is the least compared to other aminoglycosides
Uses of kanamycin?
1- treatment of tuberculosis if bacteria is resistant to other anti T.B.
2- used orally for prophlaxis in cases of hepatic coma
Dose of kanamycin in TB ?
1 g daily
Dose of kanamycin in prophlaxis ?
4-6 grams daily ( in divided doses ) for 36 to 27 hours
Therapeutic Uses of streptomycin ?
Therapentic uses of streptomycin are now restricted to :
1- bacterial endocarditis : in combination with penicillins
2- tuberculosis : in combination with isoniazed
3- plague