Clindamycin : This potent lincosamide antibiotic is similar in mechanism of action (inhibits protein synthesis by binding to 50S ribosome) and spectrum of activity to erythromycin with which it exhibits partial cross resistance.
LINCOSAMIDE ANTIBIOTICS
Clindamycin
This potent
lincosamide antibiotic is similar in mechanism of action (inhibits protein
synthesis by binding to 50S ribosome) and spectrum of activity to erythromycin
with which it exhibits partial cross resistance. Modification of the ribosomal
binding site by constitutive methylase enzyme confirs resistance to both. It
inhibits most gram-positive cocci (including penicillinase producing Staph., but not MRSA), C. diphtheriae, Nocardia, Actinomyces, Toxoplasma, but the distinctive feature is
its high activity against a variety of anaerobes, especially Bact. fragilis. Aerobic gram-negative
bacilli, spirochetes, Chlamydia, Mycoplasma and Rickettsia are not affected.
Oral absorption of
clindamycin is good. It penetrates into most skeletal and soft tissues, but not
in brain and CSF; accumulates in neutrophils and macrophages. It is largely
metabolized and metabolites are excreted in urine and bile. The t½ is 3 hr.
Side effects are
rashes, urticaria, abdominal pain, but the major problem is diarrhoea and
pseudomembranous enterocolitis due to Clostridium
difficile superinfection which is potentially fatal. The drug should be promptly stopped and metronidazole
(alternatively vancomycin) given to treat it.
Because of potential toxicity, use of clindamycin is restricted
to anaerobic and mixed infections, especially by Bact. fragilis causing abdominal, pelvic and lung abscesses. It is
generally combined with an aminoglycoside or cephalosporin. Metronidazole and
chloramphenicol are the alternatives to clindamycin for covering the anaerobes.
Anaerobic streptococcal and Cl.
perfringens infections and those involving bone and joints respond well. It
has also been employed for prophylaxis of endocarditis in penicillin allergic patients
with valvular defects who undergo dental surgery, as well as to prevent
surgical site infection in colorectal/pelvic surgery.
In AIDS patients, it has
been combined with pyrimethamine for toxoplasmosis and with primaquine for Pneumocystis jiroveci pneumonia.
Topically it can be used for infected acne vulgaris.
Clindamycin, erythromycin and chloramphenicol can exhibit mutual
antagonism, probably because their ribosomal binding sites are proximal;
binding of one hinders access of the other to its target site. Clindamycin
weakly potentiates neuromuscular blockers.
Dose: 150–300 mg QID oral;
200–600 mg i.v. 8 hourly; DALCAP 150 mg cap; CLINCIN
150, 300 mg cap; DALCIN 150, 300 mg cap, 300 mg/2 ml and 600 mg/ 4 ml inj.
Lincomycin
It is the forerunner of clindamycin; has similar antibacterial
and toxic properties, but is less potent and produces a higher incidence of
diarrhoea and colitis—deaths have occurred. Thus, it has been largely replaced
by clindamycin. It is absorbed orally and excreted mainly in bile; plasma t½ 5 hrs.
Dose: 500 mg TDSQID oral;
600 mg i.m. or by i.v. infusion 6–12
hrly.
LINCOCIN 500 mg cap, 600 mg/2 ml inj; LYNX 250, 500 mg cap, 125
mg/5 ml syr, 300 mg/ml inj in 1, 2 ml amp.
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