ANTI MICROBIAL COMBINATION THERAPY

There is certain rational behind the simultaneous use of two or more antibiotics in specific situations. As the various groups of drugs exhibit their different effects on micro organisms, one drug may have the potential to either inhibit or enhance the effect of crude drug. Likewise, the combination of antibiotics that selected to treat the infection, may have additive or supra additive toxicities e.g. Vancomycin exerts minimal nephrotoxicity when given alone but when in combination with tobramycin (aminoglycoside), the combination cause marked renal function impairment.

Following are the clinical indications for the use of combination of antibiotics. In fact, there are only few of numerous reasons given to justify the rational use of antimicrobial combination.

Treatment Of Mixed Bacterial Infection:

Some infections are caused by two or more than two microorganisms. These include intra abdominal, hepatic and brain abscesses and infection of the genital tract. In these cases it becomes necessary to use different drugs with different antimicrobial spectra to achieve desired breadth of activity.

Therapy Of Severe Infection Of Unknown Cause:

Combination therapy is most commonly employed in empirical therapy of those infections whose causative agent has not been or can’t be identified. In such situation, the prime objective of the treatment is to provide the broader antimicrobial coverage for microorganisms that are most likely to cause infection.

Selection of therapy must be made on clinical judgment of the physician, which obviously reflects the knowledge of the signs and symptoms and microbiology of the disease, and spectrum of available drugs.

The continuation of combination therapy becomes mandatory in cases when physician fails to obtain adequate culture before initiating empirical therapy. However prolong use of multiple therapy may lead to over use of toxic and expensive drugs.

Enhancement Of Antibiotic Acting In The Treatment Of Specific Infection:

Synergistic effect of expertly designed suitable combination of a drug is used to treat certain specific infections. The use of such combinations is based on the documented proof of efficacy e.g. penicillin + streptomycin produce synergistic effect against streptococci.

Also sulfonamides with Trimethoprim are synergistic in vitro and the combination is effective against infection caused by microorganisms, which might be resistant to sulfonamide alone.

Prevention Of Emergence Of Resistant Micro organisms:

The use of combination therapy was first proposed as a tool to prevent the emergence of resistant mutants during therapy. This approach has been extensively used in the treatment of TB where co-current use of two or more appropriate drugs markedly reduces the probability of development of drug resistance in mycobacterium tuberculosis