MONENSIN
Overview
Synonyms
Monensin A sodium salt;Monensin sodium;Monensin sodium salt
NSC 343257;Sodium monensin
Functional Class
Veterinary Drug
ANTIMICROBIAL_AGENT
ANTIMICROBIAL_AGENT
Evaluations
Evaluation year: 2012
ADI:0-0.01 mg/kg bw
ADI:
0-0.01 mg/kg bw
Comments:
The 70th Committee meeting considered monensin A to be a suitable marker residue in both milk and tissues. The Committee at its present meeting reviewed two new residue depletion studies and previously-assessed residue depletion studies in cattle, in particular those using a combination of intraruminal controlled-release capsule and administration via feed. Based on the controlled-release capsule alone residue study, the Committee revised the MRL for cattle liver to be 100 μg/kg, as monensin A. Combined use of the capsule and feed premix in cattle at the highest reported dose will likely result in liver residues exceeding the revised MRL. Without any additional data, the Committee was unable to revise the current MRLs for goats & sheep. Using the revised MRL for cattle, the recalculated TMDI was 481 μg/p/d (80% of the ADI).
MRL Comment:
MRL for cattle liver to 100 μg/kg, as monensin A.
Intake:
Recalculated TMDI: 481 μg/p/d
Meeting:
75
Report:
Residues:
Evaluation year: 2008
ADI:
0-0.01 mg/kg bw
Comments:
The Committee considered the consistent decrease in body weight gain at lower doses as a conservative indicator of monensin toxicity, even though the exact mechanism of this effect is not known. The Committee selected the lowest relevant NOAEL of 1.14 mg/kg bw/d in the 2-year oral rat study, based on a decrease in body weight gain at the next higher dose, as the basis for derivation of the ADI. The Committee established an ADI of 0–10 μg/kg bw on the basis of this NOAEL and a safety factor of 100, rounding to one significant figure. Using the model diet and marker to total residue ratios of 5% (tissues) and 2.7% (milk), the recommended MRLs would result in an intake of 0.301 mg/p/day (poultry tissues + milk) or 0.321 mg/p/day (ruminant tissues + milk), 50% and 54% of the ADI, respectively.
MRL Comment:
Recommended maximum residue limits (MRLs) for
-Cattle, Sheep and Goats: Fat 100 (μg/kg), Kidney 10 (μg/kg), Liver 20 (μg/kg), Muscle 10 (μg/kg) and Milk 2 (μg/L)
- Chicken, Turkey and Quail: Fat 100 (μg/kg), Kidney 10 (μg/kg), Liver 10 (μg/kg), Muscle 10 (μg/kg)
Intake:
TMDI: 0.301 mg/pday (poultry tissues + milk) or 0.321 mg/p/day (ruminant tissues + milk)
Report:
Tox Monograph:
Specification:
Toxicological study
Pivotal Study:
GLP-compliant 2-years study (Howard et al., 1981): 5- to 6-week-old Wistar rats (80-120/sex/group) were maintained on a diet
containing 0, 25, 56 or 125 mg crystalline monensin sodium/kg for 2 years (time-weighted average daily dose: 0, 1.14, 2.57 and 5.91 mg/kg bw/d (males) and 0, 1.46, 3.43 and 8.68 mg/kg bw/d (females)). Bodyweight and weight gain were significantly decreased in animals receiving 125 mg monensin/kg in their diet and were transiently decreased during the first 4 months
in rats in the middle dose group. Feed conversion efficiency was decreased at 56 or 125 mg monensin/kg in the diet, and mean feed consumption was decreased in animals in the highest dose group during the first 5 weeks of the trial. A NOAEL of 25 mg/kg (1.14 mg/kg bw/day) was identified based on the effects on body weight .
Animal Specie:
Rats
Effect:
Decreased bodyweight gain
NOAEL:
1.14 mg/kg bw/day
Point of departure:
1.4 mg/kg bw/d