328 Section 9/ ChemotherapyIt is bactericidal drug and exerts its
action by combining with bacterial
ribosome and induces misreading of
mRNA codons. Also in sensitive bacteria,
disruption of cytoplasmic membrane occurs
resulting in leakage of amino acids, ions,
leading to bacterial death.
After oral administration it is not
absorbed. After IM injection the absorption
is rapid. It is excreted unchanged in urine.
Half life is prolonged in patients of renal
failure.
Adverse effects include pain at
injection site, ototoxicity, nephrotoxicity,
skin rash, fever, exfoliative dermatitis and
eosinophilia. Anaphylaxis is rarely seen.
Optic nerve dysfunction.
It is used in all forms of tuberculosis
along with other antitubercular drugs.
Other indications are tularemia, plague,
brucellosis, bacterial endocarditis, entero-
coccal endocarditis. Used concomitantly
with penicillin G for synergistic effect in the
treatment of enterococcal endocarditis
when other antibiotics are ineffective or
contraindicated.
GENTAMICIN
It is obtained from Micromonospora
pupurea. It has broader spectrum of action
and is effective against Pseudomonas
aeruginosa, E. coli, Klebsiella, Enterobacter
and Proteus. Streptococci and enterococci
are relatively resistant to it owing to failure
of the drug to penetrate into the cell.
Following parenteral administration, it
defuses mainly into extracellular fluids.
It is valuable in critically ill patients
with impaired host defence; Pseudomonas
or Proteus infections in burns, urinary tract
infections, lung abscesses, osteomyelitis,
middle ear infection, septicaemia; menin-
gitis caused by gram negative bacilli, peri-
tonitis, in skin and soft tissue infections and
postoperative infection.
Topical administration in the form of
drop and ointment have been used for the
treatment of infected burns, wounds and
the prevention of intravenous catheter
infections and in the treatment of ocular
infections.
Adverse effects include ototoxicity (in-
cidence is related to dose and duration of
therapy), nephrotoxicity, hypersensitivity
reactions, skin itching, headache, neuromus-
cular junction blockade, anorexia, nausea,
vomiting, superinfection, photosensitivity,
drowsiness, weakness, thrombocytopenia,
agranulocytosis.TOBRAMYCIN
It belongs to family nebramycins, is
isolated from Streptomyces tenebrarius. Its
antibacterial activity is similar to
gentamicin and slightly more active than
gentamicin against Pseudomonas aeruginosa
and Proteus.
It is used in the treatment of infection
of gastrointestinal and respiratory tract,
skin and soft tissue infections, septicaemia
and urinary tract infection.
Adverse effects include skin rash,
ototoxicity, nephrotoxicity, phlebitis,
nausea, vomiting, urticaria and headache.
Ototoxicity and nephrotoxicity is lower
than gentamicin.