Vancomycin : It is a glycopeptide antibiotic discovered in 1956 as a penicillin substitute which has assumed special significance due to efficacy against MRSA, Strep. viridans, Enterococcus and Cl. difficile.
GLYCOPEPTIDE ANTIBIOTICS
Vancomycin
It is a glycopeptide
antibiotic discovered in 1956 as a penicillin substitute which has assumed special
significance due to efficacy against MRSA, Strep.
viridans, Enterococcus and Cl.
difficile. It is bactericidal to gram-positive
cocci, Neisseria, Clostridia and diphtheroids. However, in
hospitals where it has been
extensively used for surgical prophylaxis, etc., vancomycin-resistant Staph. aureus (VRSA) and vancomycin-resistant Enterococcus (VRE) have emerged. These nosocomial bacteria are resistant to methicillin
and most other antibiotics as well.
Vancomycin acts by
inhibiting bacterial cell wall synthesis. It binds to the terminal dipeptide ‘Dala-Dala’
sequence of peptidoglycan units— prevents its release from the bactoprenol
lipid carrier so that assembly of the units at the cell membrane and their cross
linking to form the cell wall cannot take place. Enterococcal resistance to vancomycin is due to a
plasmid mediated alteration of the dipeptide target site, reducing its affinity
for vancomycin.
Vancomycin is not
absorbed orally. After i.v. administration, it is widely distributed,
penetrates serous cavities, inflamed meninges and is excreted mainly unchanged
by glomerular filtration with a t½ of 6 hours. Dose reduction is needed in
renal insufficiency.
Toxicity: Systemic toxicity of vancomycin is high. It can cause plasma concentrationdependent
nerve deafness which may be permanent. Kidney damage is also doserelated. Other
oto and nephrotoxic drugs like aminoglycosides must be very carefully administered
when vancomycin is being used. Skin allergy and fall in BP during i.v.
injection, due to histamine release from mast cells, are the other problems. Rapid
i.v. injection has caused chills, fever, urticaria and intense flushing—called
‘Red man syndrome’.
Uses:
Given orally (125–500
mg 6 hourly), it is the second choice drug
to metronidazole for antibiotic associated pseudomembranous enterocolitis caused
by C. difficile.
Systemic use (500 mg 6
hourly or 1 g 12 hourly infused i.v. over 1 hr) is restricted to serious MRSA
infections for which it is the most effective drug, and as a penicillin
substitute (in allergic patients) for enterococcal endocarditis along with
gentamicin. For empirical therapy of bacterial meningitis, i.v. vancomycin is
usually combined with i.v. ceftriaxone/cefotaxime. It is also used in dialysis
patients and those undergoing cancer chemotherapy. Penicillin-resistant pneumococcal
infections and infection caused by diphtheroids respond very well to vancomycin.
It is the preferred
surgical prophylactic in MRSA prevalent areas and in penicillin allergic
patients.
VANCOCIN-CP 150 mg tab, 500 mg/vial inj; VANCOGEN, VANCORID-CP
500 mg/vial inj; VANCOLED 0.5, 1.0 g inj.
Teicoplanin
It is a newer glycopeptide antibiotic which in fact
is a mixture of 6 similar compounds. It is active against gram-positive
bacteria only; mechanism of action and spectrum of activity is similar to vancomycin.
Notable features are:
· It is more active than
vancomycin against enterococci, and equally active against MRSA.
· Some VRE but not VRSA
are susceptible to teicoplanin.
· It can be injected
i.m. as well; is excreted by kidney; dose needs to be reduced in renal insufficiency;
has a very long t½ (3–4 days).
· Toxicity is less than
vancomycin; adverse effects are rashes, fever, granulocytopenia and rarely
hearing loss. Reactions due to histamine release are rare (1 in 2500).
Teicoplanin is indicated in enterococcal endocarditis (along
with gentamicin); MRSA and penicillin resistant streptococcal infections, osteomyelitis,
as alternative to vancomycin.
Dose: 400 mg first day—then
200 mg daily i.v. or i.m.; severe
infection 400 mg × 3 doses 12 hourly—then 400 mg daily.
TARGOCID 200, 400 mg
per vial inj. for reconstitution.
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