Aminoglycosides are a class of bactericidal antibiotics that inhibit protein synthesis in gram-negative aerobic bacteria. They are highly polar compounds that are poorly absorbed from the GI tract and must be administered parenterally. They are effective against aerobic gram-negative bacilli but not anaerobes. Common side effects include ototoxicity and nephrotoxicity. Resistance can develop through bacterial enzyme inactivation of the drug, decreased drug entry into cells, or decreased drug affinity for ribosomes.

2. Introduction
• Bactericidal Protein synthesis inhibiting drug mainly (Gram-negative aerobes)
• History:-
• Two amino sugar joined to a non-sugar moiety by glycosidic bond (-O-)
• Drugs-Streptomycin, Gentamicin, Tobramycin, Amikacin, Kanamycin,
Sisomicin, Neomycin (T), Framycetin (T) and Netilmicin, Paromomycin

3. -:Common properties of aminoglycosides:-
1. They are highly polar compounds, hence, poorly absorbed from the GI tract.
2. Effective mainly against:-Aerobics Gm-Negative (bacilli)
3. Administered-Parenteral route (i.m. /i.v.) for systemic effect.
4. Poor penetrate into the CSF & BBB
5. Not metabolized in body so excreted unchanged in urine
6. Exhibit Ototoxicity and Nephrotoxicity
7. Exhibit partial cross-resistance among them.
8. Transport of aminoglycosides across cytoplasmic membrane requires oxygen &
energy hence “anaerobes are resistant to aminoglycosides”

4. • MOA:-
They process concentration dependent killing i.e.higher conc. Kills more bacteria at rapid rate
Also process Post Antibiotic effect

5.  Development of Resistance by-
• inactivation of the drug by bacterial enzymes
• ↓ entry of drug into bacterial cell
• ↓ affinity of the drug for the ribosomes
 Antibacterial spectrum:-
 gram- ve aerobic bacilli except salmonella
 Gram+ ve cocci e.g.-S aureus & streptococcus viridians
 Not effective against anaerobes
 Pharmacokinetics:-
 Absorption-Highly polar not absorbed orally (parental use i.m.
/i.v.)
 Distribution- poor penetration to CSF & Intraocular fluid
 Metabolism- not in body
 Excretion-kidney (high conc. In urine so useful in UTI & dose
reduction needed in renal failure)

6. • Therapeutic uses:-
1. Dental uses:- (not commonly use)
• Prophylaxis of bacterial endocarditis- combination with penicillin(amoxicillin)
(Penicillin G+ gentamicin)
• Prosthetic heart valves
Side effect:-
• Ototoxicity:- more likely due to prolonged use,toxicity ,renal failure

7. • Vestibular and cochlear dysfunctions can occur due to VIII- cranial nerve damage
• They get concentrated in the perilymph and endolymph of the inner ear
• Nephrotoxicity:- reversible
• Highest→ neomycin(not indicated for systemic use)
• least →streptomycin
• Risk factor- Hypokalemia, Renal disease, concomitant nephrotoxic drugs-e.g.-
Amphotericin-B, Vancomycin, ACE-I, Cisplatin, cyclosporine
• NM-blocked-Apnoea and muscular paralysis
Cochleotoxic
Vestibulotoxic
Amikacin, kanamycin, Neomycin
(Hearing loss)
All other aminoglycosides (maximum by
streptomycin & Gentamicin)

8. • Myasthenic patients are more susceptible to neuromuscular blocking effect of
these drugs, hence should be avoided
• Hypersensitivity reactions:- are rare; occasionally skin rashes, drug fever and
eosinophilia can occur.
• Cross sensitivity between aminoglycosides may occur.
• Use of aminoglycosides during pregnancy may cause ototoxicity in the foetus
• Streptomycin:-
• Streptomycin was the first aminoglycoside discovered in 1944.
• Uses:- first-line drugs for TB and is used in combination with other
antitubercular drugs.
• Tularaemia, plague and brucellosis.

9. • Gentamicin:-most commonly used aminoglycoside antibiotic for aerobic gram-
negative bacillary infections
• It is also effective against gram-positive
• Infections—enterococci, S. viridans and staphylococci but not M. tuberculosis.
• Neomycin:-highly nephrotoxic(No systemic use)
• Used topically in combination with bacitracin or polymyxin B for wounds, ulcers,
burns, and infections of eye and ear.
• Amikacin:-broadest spectrum aminoglycoside.
• It is useful for the treatment of nosocomial gram-negative infections and TB
(Anti-TB drugs)