Concurrent use of two dual-combination drenches containing monepantel/abamectin and oxfendazole/levamisole in sheep: effect on marker residues 21 and 28 days after administration

Figures & data

Table 1. Dose (mg/kg) of monepantel, abamectin, levamisole and oxfendazole administered to individual sheep in a trial to determine the concentration of anthelmintic marker residues in target tissues following concurrent dosing with two dual-active oral drenches.

Group	Slaughter day	Animal ID	Sex	Dose (mg/kg)
				Zolvix Plus^a		Scanda^b
				Monepantel	Abamectin	Levamisole^c	Oxfendazole
1	21	2281	M	2.59	0.21	7.34	4.82
		2282	F	2.58	0.21	7.33	4.81
		2292	M	2.60	0.21	7.36	4.84
		2295	F	2.60	0.21	7.41	4.86
		2296	F	2.61	0.21	7.30	4.79
		2334	M	2.57	0.21	7.28	4.78
2	28	2278	F	2.56	0.20	7.41	4.86
		2287	F	2.57	0.21	7.25	4.76
		2297	M	2.56	0.20	7.36	4.84
		2299	M	2.55	0.20	7.32	4.80
		2335	M	2.53	0.20	7.18	4.72
		2336	F	2.59	0.21	7.28	4.78

^a Active ingredients: 25 g/L monepantel, 2 g/L abamectin equating to a dose of 2.5 mg/kg monepantel and 0.2 mg/kg abamectin when dosed at the label rate of 1 mL/kg.

^b Active ingredients: 80 g/L levamisole hydrochloride (equivalent to 69 g/L levamisole), 45.3 g/L oxfendazole equating to a dose of 6.9 mg/kg levamisole and 4.53 mg/kg oxfendazole when dosed at the label rate of 1 mL/kg.

^c Expressed as levamisole equivalent (not levamisole hydrochloride).

F = female; ID = identification number; M = male.

Table 2. Limits of detection (LOD) and quantitation (LOQ) and maximum residue limits (MRL) of actives in a trial to determine the concentration of anthelmintic marker residues in target tissues of sheep following concurrent dosing with two dual-active oral drenches.

	Method					MRL^a (μg/kg)
Active	LOQ (μg/kg)	LOD (μg/kg)	Calibration range (μg/kg)	Coefficient of determination (R^2)	Analyte(s)	Liver	Fat
Monepantel	10	3	3–1,000	0.9993	Monepantel sulfone	5,000	7,000
Abamectin	0.5	0.25	0.25–100	0.9998	Avermectin B1a	25	50
Levamisole	10	3	3–1,000	0.9980	Levamisole	100	10
Oxfendazole	32	9.5	3–600	0.9985	Sum of^b oxfendazole, fenbendazole and fenbendazole sulfone	500	50

^a MPI 2023b.

^b Expressed as fenbendazole sulfone.

Table 3. Mean residues (μg/kg) of monepantel sulfone, abamectin, levamisole and oxfendazole in liver and fat of sheep sacrificed 21 (n = 6) and 28 (n = 6) days after concurrent administration of two dual-active drenches.

		Day 21				Day 28
	MRL^a	n > LOQ^b	Min	Max	Mean^c (SD^d)	n > LOQ^b	Min	Max	Mean^c (SD^d)
Liver
Monepantel sulfone	5,000	6	110	388	232 (102)	4	45.1	170	90.2 (49.7)
Abamectin^e	25	1	0.795	0.795	0.795	0	< LOQ	< LOQ	< LOQ
Levamisole	100	3	14.3	78.3	40.0	1	10.0	10.0	10.0
Oxfendazole^f	500	6	51.3	165	98.7 (39.0)	6	25.1	53.6	39.1 (9.8)
Fat
Monepantel sulfone	7,000	6	242	1,119	644 (314)	5	14.9	868	380 (320)
Abamectin^e	50	2	0.514	1.46	0.987	0	< LOQ	< LOQ	< LOQ

^aMPI 2023b.

^b LOQ = 0.5 μg/kg for abamectin, 10 μg/kg for all other analytes.

^c Calculated on values > LOQ only.

^d Only calculated for analytes when n > LOQ was > 4.

^e Avermectin B1a residues only.

^f As calculated fenbendazole sulfone, converted using a factor of 1.05 from detected oxfendazole and 1.11 from detected fenbendazole.

*MPI. Maximum Residue Levels for Agricultural Compounds. https://www.mpi.govt.nz/dmsdocument/19550-Maximum-Residue-Levels-for-Agricultural-Compounds (accessed 14 June 2023). Ministry for Primary Industries, Wellington, NZ, 2023b

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