Nuflor® vs. Micotil® or Naxcel®: Clinical Trial Results

Bovine respiratory disease (BRD) is a complex interaction of bacteria, viruses and distressors such as environment, management and nutrition. The disease is characterized by fever, respiratory distress, reduced performance, medical expenses and mortality. It is widely recognized that effective early treatment is imperative in reducing the economic loss associated with this disease.

Florfenicol is an antibiotic that has shown a high degree of activity against the important bacteria associated with BRD. The MIC90 against Mannheimia (Pasteurella) haemolytica is 1.0 mcg/ml, and against Pasteurella multocida and Haemophilus somnus the MIC90 is 0.5 mcg/ml. NUFLOR is a unique formulation of florfenicol that provides prolonged activity. NUFLOR given at the recommended dose of 20 mg/kg provides therapeutic serum, bronchial secretion and lung tissue levels in cattle. Levels are greater than the MIC of BRD pathogens within 1 to 2 hours post injection and are maintained throughout the majority of the treatment period.


The purpose of this trial was to compare the efficacy of NUFLOR, Micotil and Naxcel for treatment of BRD in a feedlot situation in central Nebraska. The study was conducted in the fall and winter 1995/1996, using calves averaging 646 lbs from the central and western United States As animals were presented with clinical signs of respiratory disease and fever of 40.5°C or greater, they were randomly (computer-generated) assigned to treatment groups. The study was blinded since the evaluators and individuals administering treatments were different.

Dosages administered were: NUFLOR 20 mg/kg IM repeated in 48 hours; Micotil 10 mg/kg SC once; Naxcel 2.2 mg/kg IM daily for 3 days. Animals that did not respond or relapsed were retreated with the same drug for up to 2 additional courses of therapy. Necropsies were performed on cattle that died and cause of death determined. Animals that did not respond after 2 retreatments or were severely debilitated were considered chronic and removed from further evaluation in this study. Average duration of the trial was 72 days from initial enrollment into the trial.


Results are presented in Table 1. NUFLOR showed statistically significant differences vs Naxcel in first treatment response (p=0.0035), final response (p=0.0001), BRD deaths (p=0.0333), H. somnus deaths (p=0.0286) and total respiratory deaths (p=0.0013). Statistical differences of NUFLOR over Micotil were noted in final treatment response (p=0.0036), BRD deaths (p=0.0182) and total respiratory related deaths (p=0.0041). There was a trend toward significance of NUFLOR over Micotil in first treatment response (p=0.0557). There was no statistical significance between NUFLOR and Micotil in H. somnus mortality. No adverse effects were reported in any treatment group.


This trial demonstrated the safety and efficacy of NUFLOR as a stand-alone treatment for BRD. Significantly different results were obtained vs Naxcel or Micotil in the economic parameters of reducing total respiratory related mortality and improving response to treatment. There were considerably more Haemophilus somnus related deaths in the Naxcel and Micotil treated groups, showing the activity of florfenicol against this pathogen.

NUFLOR is a registered trademark of Intervet Inc.

MICOTIL is a registered trademark of Eli Lilly and Company.

NAXCEL is a registered trademark of Pharmacia & Upjohn.