Aminoglycosides

Question 1

Enumarate Aminoglycoside?

Answer 1

1. Streptomycin
2. GENTAMYCIN
3. Amikacin
4. Kanamycin

Question 2

MOA Of aminoglycoside ?

Answer 2

Entry of aminoglycosides into bacterial cell (02 is required)
Bind to 3OS ribosomal subunit
Inhibit initiation of protein synthesis
Cause misreading of codon
Premature termination of protein synthesis
Insertion of wrong amino acid into the growing peptide chains
Formation of defective proteins
Incorporation of defective proteins into bacterial cell membrane
Altered permeability and disruption of cell membrane (bactericidal

Question 3

Therapeutic effect of aminoglycoside ?

Answer 3

Gentamin, tobramycin, amikacin and netilmicin are effective against P. aeruginosa.
•
Antani and netimicin are used for treatment of serious nosocomial infections due to
• gram-negative bacilli:
Aming lycosides are often used in combination with penicillins/ third generation cepha: losporins in these conditions:
Bacterial endocarditis due to 5, viridans and Enterococcus: Gentamicin is used in combination with a penicillin or vancomycin. Combination broadens the spectrum of activity, produces synergistic effect and decreases emergence of resistance.
→ PenicillinG + gentamicin for S. viridans
• Ampicillin” + gentamicin for Enterococcus.
→ Vancomycin + gentamicin for Enterococcus (patients allergic to B-lactam antibiotics).
Gentamicin and ampicillin combination is also used for the prophylaxis of endocarditis in high-risk patients before surgical procedures.
TB: Streptomycin, kanamycin and amikacin are used in the treatment of TB.
Other gram-negative infections:
• Plague: Streptomycin/ gentamicin is used intramuscularly.
• Brucellosis: Streptomycin/ gentamicin is used in combination with doxycycline.
• Tularaemia: Streptomycin or gentamicin is the drug of choice. FQs and tetracyclines

Question 4

Adverse effects of aminoglycosides

Answer 4

totoxicity: Vestibular and cochlear dysfunctions can occur due to VIIIth cranial nerve dan-age. Aminoglycosides get concentrated in the perilymph and endolymph of the inner eas which can lead to progressive damage to vestibular and cochlear hair cells Streptomycinand gentamicin mainly affect vestibular function. Vestibular dysfunction causes intense headache (earliest symptom), dizziness, nausea, vomiting, vertigo, nystagmus and ataxia. Amikain and kanamycin affect auditory function, causing more cochlear damage. The manifestations of cochlear damage are tinnitus (reversible on discontinuation of the drug) and deafness (permanent).
The important risk factors for ototoxicity are (a) elderly patients; (b) repeated courses of aminoglycosides; (c) persistently increased concentration of the drug in plasma; ($ patients with preexisting auditory impairment; (e) concurrent use of other ototoxic drugs, such as vancomycin, minocycline and loop diuretics.
2. Nephrotoxicity: Aminoglycosides get concentrated in renal cortex and produce nephrotox-icity, which is usually reversible on discontinuation of the drug. The incidence of nephro-toxicity is highest with neomycin and least with streptomycin. There is a decrease in urinary concentrating capacity, albuminuria, etc. The risk factors for nephrotoxicity are elderly patients, preexisting renal disease and concurrent use of other nephrotoxic drugs, such as AMB, vancomycin, cisplatin and cyclosporine.
3. Neuromuscular blocking effect: Apnoea and muscular paralysis have been reported. F may be reversed by administration of calcium salt. Aminoglycosides inhibit release of are-tyicholine from motor nerve. Myasthenic patients are more susceptible to neuromuscular blocking effect of these drugs; hence, they sHould be avoided.
4. Hypersensitivity reactions are rare; occasionally skin rashes, itching, drug fever and er sinophilia can occur. Cross-sensitivity between aminoglycosides may occur.
5. Use of aminoglycosides during pregnancy may cause ototoxicity in fetus avoid dunts pregnancy).
6. Aming lycosides are not compatible with other drugs; hence, these should not muslin