Drug synergism is seen in all except:
|A||Flucytosine and amphotericin B for cryptococcal|
|B||Trimethoprim and sulphamethoxazole for UTI|
|C||Penicillin and aminoglycoside|
|D||Chlortetracycline + penicillin|
Drug Synergism: When the action of one drug is facilitated or increased by the other, they are said to be synergistic. In a synergistic pair, both the drugs can have action in the same direction or given alone one may be inactive but still enhance the action of the other when given together.
Now, considering each option- separately
Option ‘a’ Flucytosine has supra-additive action with AMB in the case of fungi sensitive to both, e.g.
Cryptococcoses, Coccidioidomycosis. (AMB increases the penetration of 5-FC into the
Option ‘b’ Sulfamethoxazole was selected for combining with trimethoprim because both have nearly
the same t1/2 (- 10 hr); Optimal synergy in case of most organisms is exhibited at a
concentration ratio of sulfamethoxazole 20 : trimethoprim 1, the MIC of each component
may be reduced by 3-6 times.
Option ‘b’ Penicillin/ampicillin + streptomycin/gentamicin is combined for use in enterococcal
Option 'd' This is the wrong answer. No synergism is reported for chlortetracycline + penicillin.
Other important antimicrobial combinations
- Carbenicillin/ticarcillin + gentamicin for pseudomonas infection, specially neutropenic patients.
- Ceftazidime + ciprofloxacin for pseudomonas infected orthopaedic prosthesis.
- Rifampicin +INH in tubercular infection.