Flora penicillin effects

The committee recommended a comparison of subtherapeutic with therapeutic use of antibiotics on the prevalence of resistant transfer factors in meat animals. Also recommended was a study comparing the enteric flora of vegetarians and meat-eaters. A third study would involve workers in abattoirs and their contacts. These studies are in progress under the direction of Dr. Edward Kass at Harvard University and investigators at the Loma Linda Medical School. The committee also recommended further research on the mechanisms of the antibiotic growth effect. The report (7) said there is little indication that sale of antibiotics, including penicillin and tetracyclines, for feed and veterinary use, "has decreased as a result of the Swann Report."... 

Absorption Most of the penicillins are incompletely absorbed after oral administration and reach the intestine in sufficient amounts to affect the composition of the intestinal flora. However, amoxicillin is almost completely absorbed. Consequently, it is not appropriate therapy for the treatment of shigella- or salmonella-derived enteritis, since therapeutically effective levels do not reach the organisms in the intestinal crypts. Absorption of penicillin G and all the penicillinase-resistant penicillins is decreased by food in the stomach since gastric emptying time is reduced and the drugs are destroyed in the acidic environment. Therefore, they must be administered 30-60 minutes before meals or 2-3 hours postprandially. Other penicillins are less affected by food. 

Not understood. The interaction between nafcillin and warfarin is possibly due to increases in the metabolism of warfarin by the liver. Dicloxacillin also possibly reduces serum warfarin levels. Other penicillins (ampicillin, benzylpenicillin, carbenicillin, methicillin, ticarcillin ) have caused increased bleeding times when given alone, principally due to platelet inhibition, which might be additive with the effects of oral anticoagulants. Broad-spectrum antibacterials may decrease the gut flora and thereby possibly decrease production of vitamin K. Other factors relating to the disease may be important, see Coumarins -i- Antibacterials p.365. 

Absorption - use of broad-spectrum antibiotics (e.g. penicillin) may, through an effect of bacterial flora in the gut, result in reduced absorption and effectiveness of oral contraceptives. 

---