Antheiminics (Dewormers)
SOURCE:
"Practice Tips Related to Medications in Goats - Medications Used in Goats"
By Seyedmehdi Mobini, DVM, MS, Diplomate ACT
GA Small Ruminant Research and Extension Center, Fort Valley State University of Fort Valley, GA
Presented to the North American Veterinary Conference, January 2000.
Also printed in summary in The American Assoc of Small Ruminant Practioners
October-December 2000 issue of Wool &Wattles the AASRP Newsletter.
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1. AVEFFNECTINS: BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Ivermectin * Ivermec drench extra- label 0.13mg/lb (0.3mg/kg) PO 36-40 days 11 days
Tvermactin Ivomec 1% extra- label 0.13mg/lb (0.3mg/kg) SC 36-40 days 56 days
Doramectin * Dectomax extra- label 0.13mg/lb (0.3mg/kg) SC 36-40 days 56 days
Eprinomectin ** Eprinex extra- label 0.22mg/lb (5mg/kg) PO 0 days 0 days
Moxidectin * Quest, Cydectin extra- label 0.22mg/lb (5mg/kg) PO 0 days ?
2. BENZIMIDAXOLES BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Albendazole Valbazen extra- label 4.5mg/lb (10mg/kg) PO 5 days 27 days
Fenbendazole Panacur/Safeguard approved 4.5mg/lb (10mg/kg) PO 4 days 14 days
Oxfendazole Synantwic extra- label 4.5mg/lb (10mg/kg) PO 5 days 14 days
3. CHOLINERGIC AGONISTS BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Levamisole Levasole extra- label 3.6mg/lb (8mg/kg) PO 4 days 10 days
Morantel Tartrate Rumatel approved 0.5mg/lb (10mg/kg) PO 0 days 30 days
* Milk kinetics of moxidectin & doramectin in goats
* Milk kinetics of moxidectin & doramectin in goats
* Pharmacokinetics of moxidectin & doramectin in goats
*Thermal and long-term freezing stability of ivermectin residues in sheep milk
** Eprinomectin in goat: assessment of subcutaneous administration (Parasitology Research 2003)
Eprinomectin in dairy goats: dose influence on plasma levels and excretion in milk(Parasitology Research 2001)
Some pharmacokinetic parameters of eprinomectin in goats following pour-on administration (1999)
Comparison of selective and systematic treatments to control nematode infection of the digestive tract in dairy goats.
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Source: October - December 2000 Wool & Wattles
American Association of Small Ruminant Practitioners (AASRP)
Ray Kaplan, DVM, PhD,
Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens, GA
On the efficacy of Eprinex cattle pour-on used on goats
The systemic availability of the avermectins and moxidectin when administered topically is significantly lower in goats than in cattle. This leads to lower efficacy and longer subtherapeutic residual levels - a perfect situation for selecting for resistant worms. This will be especially important if there is a history of ivermectin use since resistance genes are already accumulating in the worm population.
Yes these pour-ons will kill parasites and should not cause adverse reactions in goats. However, choosing this route of administration all but a rare instance will almost certainly hasten the appearance of avermectin-resistant parasites in the herd. With the ever increasing prevalence of avermectin resistance we are seeing here in the Southeast (we are starting to be surprised when ivermectin works), I think it is prudent everywhere to consider the issue of resistance every time a nematode control strategy is implemented. We have only a few drugs and cannot look forward to any new drugs in the foreseeable future. Clearly more research needs to be done -- but who will fund it?
As an aside -- resistance to any of the avermectins (ivermectin, doramectin, or eprinomectin) appears to pretty much confer resistance to all of them. However, moxidectin (a milbemycin) continues to kill avermectin resistant worms -- although we expect this efficacy to be relatively short-lived.
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Source: Excerpts from FARAD Digest, Extralabel use of ivermectin and moxidectin in food animals.
Ronald E. Baynes, DVM, PhD1; Michael Payne, DVM, PhD2; Tomas Martin-Jimenez, DVM, Ph.D, DACVCP3; Ahmed-Rufai Abdullah, DVM1; Kevin L. Anderson, DVM, Ph.D, DABVP1; Alistair I. Webb, DVM, PhD, DACVA4; Arthur Craigmill, Ph.D2; Jim E. Riviere DVM, PhD1
Food Animal Residue Avoidance Databank (FARAD), 1- Department of Farm Animal Health and Resource Management, College of Veterinary Medicine, North Carolina State University, 2- Department of Environmental Toxicology, University of California, 3- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, 4- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, 4- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois.
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The Food Animal Residue Avoidance Databank (FARAD) access centers in the United States have been contacted in recent months about the extralabel use of several macrolide endectocides. The focus of this article is to provide an update on approved use of these drugs. Caution should be exercised with extralabel use of this class of drugs, particularly with moxidectin and ivermectin use in dairy animals. Macrolide endectocides are popular in livestock operations, because they are generally efficacious against most important internal and external parasites, and approved topical formulations can improve producer compliance.
Because many macrolide endectocides are lipophilic, substantial concentrations will be found in edible tissues. As much as 5% of the administered drug can be secreted in milk1. Only eprinomectin and moxidectin pour-on formulations are approved for use in dairy cattle. This is because of the intrinsic chemical behavior and unique formulation chemistry of these 2 drugs. Ivermectin and doramectin are not approved for dairy animals, and their meat withdrawal times are long compared with other less lipophilic parasiticides. Parallel disposition data of milk and plasma ivermectin indicates a milk
lasma area under the curve (AUC) ratio of 1.08 for goats2. Compared with approved oral and subcutaneous routes of administration, approved topical application can result in less absorption but extended meat withdrawal times, because the dermal absorption process is rate limiting, and depletion of residues to established tolerances is prolonged.
Extralabel Use of Ivermectin.
Oral route in goats-Ivermectin is not approved for use in goats in the United States. However, the labeled drench dose for sheep (0.2 mg/kg of body weight [0.09mg/lb]) has an 11-day meat WDT. This is supported by an observed fat and liver depletion half-life of 1.1 days for the intraruminal route in sheep,5 recalling that it generally requires about 10-half-lives to eliminate 99% of the drug. Several studies further demonstrated that following intraruminal administration in goats,6 bioavailability was 2.5 times lower and the plasma half-life was 2.3 times shorter than in sheep7. These pharmacokinetic differences were not observed with doses administered SC.2 On the basis of these supporting data, FARAD estimates that if the oral drench approved for sheep is administered to goats at the labeled dose for sheep, then a meat WDI of 11 days should prevent meat residues in goats. If ivermectin is administered at up to 1.5 to 2.0 times the labeled dose for sheep, as is the common practice, then the WDI needs to be extended by at least one extra ERH. Based on the WDT for sheep, and in the absence of tissue depletion data for goats, FARAD assumes an ERH of 2.2 days obtained by dividing the WDT by a half-life multiplier (HLM) value of 5.3,4 The HLM represents the number of ERH needed for the concentration in tissue to reach the tolerance level. In summary, FARAD recommends a meat WDI of 14 days for up to 0.4 mg/kg (0.18mg/lb) per os. These calculations assume that the kinetics of ivermectin are linear. The milk WDI would be 6 days based on a study by Scott et al,8 that demonstrated that at 6 days, goats' milk was clear of the drug after an oral dose of 0.2 mg/kg. Based on this information, oral administration up to 0.4 mg/kg will require a milk WDI of at least 8 days in dairy goats.
Subcutaneous route in goats-Ivermectin was detected up to 25 days in milk from lactating goats given 0.2 mg/kg SC.2 There were no differences between plasma and milk pharmacokinetic variables, and the milk
lasma AUC ratio was 1.08, as stated earlier. The elimination half-life was 4 days for plasma and milk, and it would take 40 days (10 half-lives) to eliminate 99% of the drug via milk when administered by this route. Limited tissue residue data from an NRSP-7 study10 provided an ERH of 4.34 days (ke = 0.1594 days-1) in fat, which is the slowest depleting tissue. Application of our algorithm resulted in a WDI of 22 days. As this FARAD estimate is less than the cattle WDT, and there were limited available data, we recommend the cattle WDT of 35 days for an extra margin of safety.
Topical route in goats-Topical application of ivemectin (0.5 mg/kg [0.23 mg/lb]) to dairy goats resulted in about 0.5 ng/ml in milk at 6 days.8 Because milk residues were not detected at 7 days, this time can be used as a milk WDI for goats given ivermectin topically. Tissues were not assayed, but plasma concentrations were less than 1.0 ng/ml at 6 days, supporting the milk-plasma relationship described.
SOURCE:
"Practice Tips Related to Medications in Goats - Medications Used in Goats"
By Seyedmehdi Mobini, DVM, MS, Diplomate ACT
GA Small Ruminant Research and Extension Center, Fort Valley State University of Fort Valley, GA
Presented to the North American Veterinary Conference, January 2000.
Also printed in summary in The American Assoc of Small Ruminant Practioners
October-December 2000 issue of Wool &Wattles the AASRP Newsletter.
--------------------------------------------------------------------------------
1. AVEFFNECTINS: BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Ivermectin * Ivermec drench extra- label 0.13mg/lb (0.3mg/kg) PO 36-40 days 11 days
Tvermactin Ivomec 1% extra- label 0.13mg/lb (0.3mg/kg) SC 36-40 days 56 days
Doramectin * Dectomax extra- label 0.13mg/lb (0.3mg/kg) SC 36-40 days 56 days
Eprinomectin ** Eprinex extra- label 0.22mg/lb (5mg/kg) PO 0 days 0 days
Moxidectin * Quest, Cydectin extra- label 0.22mg/lb (5mg/kg) PO 0 days ?
2. BENZIMIDAXOLES BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Albendazole Valbazen extra- label 4.5mg/lb (10mg/kg) PO 5 days 27 days
Fenbendazole Panacur/Safeguard approved 4.5mg/lb (10mg/kg) PO 4 days 14 days
Oxfendazole Synantwic extra- label 4.5mg/lb (10mg/kg) PO 5 days 14 days
3. CHOLINERGIC AGONISTS BRAND NAME APPROVAL DOSAGE ROUTE MILK MEAT
Levamisole Levasole extra- label 3.6mg/lb (8mg/kg) PO 4 days 10 days
Morantel Tartrate Rumatel approved 0.5mg/lb (10mg/kg) PO 0 days 30 days
* Milk kinetics of moxidectin & doramectin in goats
* Milk kinetics of moxidectin & doramectin in goats
* Pharmacokinetics of moxidectin & doramectin in goats
*Thermal and long-term freezing stability of ivermectin residues in sheep milk
** Eprinomectin in goat: assessment of subcutaneous administration (Parasitology Research 2003)
Eprinomectin in dairy goats: dose influence on plasma levels and excretion in milk(Parasitology Research 2001)
Some pharmacokinetic parameters of eprinomectin in goats following pour-on administration (1999)
Comparison of selective and systematic treatments to control nematode infection of the digestive tract in dairy goats.
--------------------------------------------------------------------------------
Source: October - December 2000 Wool & Wattles
American Association of Small Ruminant Practitioners (AASRP)
Ray Kaplan, DVM, PhD,
Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens, GA
On the efficacy of Eprinex cattle pour-on used on goats
The systemic availability of the avermectins and moxidectin when administered topically is significantly lower in goats than in cattle. This leads to lower efficacy and longer subtherapeutic residual levels - a perfect situation for selecting for resistant worms. This will be especially important if there is a history of ivermectin use since resistance genes are already accumulating in the worm population.
Yes these pour-ons will kill parasites and should not cause adverse reactions in goats. However, choosing this route of administration all but a rare instance will almost certainly hasten the appearance of avermectin-resistant parasites in the herd. With the ever increasing prevalence of avermectin resistance we are seeing here in the Southeast (we are starting to be surprised when ivermectin works), I think it is prudent everywhere to consider the issue of resistance every time a nematode control strategy is implemented. We have only a few drugs and cannot look forward to any new drugs in the foreseeable future. Clearly more research needs to be done -- but who will fund it?
As an aside -- resistance to any of the avermectins (ivermectin, doramectin, or eprinomectin) appears to pretty much confer resistance to all of them. However, moxidectin (a milbemycin) continues to kill avermectin resistant worms -- although we expect this efficacy to be relatively short-lived.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Source: Excerpts from FARAD Digest, Extralabel use of ivermectin and moxidectin in food animals.
Ronald E. Baynes, DVM, PhD1; Michael Payne, DVM, PhD2; Tomas Martin-Jimenez, DVM, Ph.D, DACVCP3; Ahmed-Rufai Abdullah, DVM1; Kevin L. Anderson, DVM, Ph.D, DABVP1; Alistair I. Webb, DVM, PhD, DACVA4; Arthur Craigmill, Ph.D2; Jim E. Riviere DVM, PhD1
Food Animal Residue Avoidance Databank (FARAD), 1- Department of Farm Animal Health and Resource Management, College of Veterinary Medicine, North Carolina State University, 2- Department of Environmental Toxicology, University of California, 3- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, 4- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, 4- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois.
--------------------------------------------------------------------------------
The Food Animal Residue Avoidance Databank (FARAD) access centers in the United States have been contacted in recent months about the extralabel use of several macrolide endectocides. The focus of this article is to provide an update on approved use of these drugs. Caution should be exercised with extralabel use of this class of drugs, particularly with moxidectin and ivermectin use in dairy animals. Macrolide endectocides are popular in livestock operations, because they are generally efficacious against most important internal and external parasites, and approved topical formulations can improve producer compliance.
Because many macrolide endectocides are lipophilic, substantial concentrations will be found in edible tissues. As much as 5% of the administered drug can be secreted in milk1. Only eprinomectin and moxidectin pour-on formulations are approved for use in dairy cattle. This is because of the intrinsic chemical behavior and unique formulation chemistry of these 2 drugs. Ivermectin and doramectin are not approved for dairy animals, and their meat withdrawal times are long compared with other less lipophilic parasiticides. Parallel disposition data of milk and plasma ivermectin indicates a milk
Extralabel Use of Ivermectin.
Oral route in goats-Ivermectin is not approved for use in goats in the United States. However, the labeled drench dose for sheep (0.2 mg/kg of body weight [0.09mg/lb]) has an 11-day meat WDT. This is supported by an observed fat and liver depletion half-life of 1.1 days for the intraruminal route in sheep,5 recalling that it generally requires about 10-half-lives to eliminate 99% of the drug. Several studies further demonstrated that following intraruminal administration in goats,6 bioavailability was 2.5 times lower and the plasma half-life was 2.3 times shorter than in sheep7. These pharmacokinetic differences were not observed with doses administered SC.2 On the basis of these supporting data, FARAD estimates that if the oral drench approved for sheep is administered to goats at the labeled dose for sheep, then a meat WDI of 11 days should prevent meat residues in goats. If ivermectin is administered at up to 1.5 to 2.0 times the labeled dose for sheep, as is the common practice, then the WDI needs to be extended by at least one extra ERH. Based on the WDT for sheep, and in the absence of tissue depletion data for goats, FARAD assumes an ERH of 2.2 days obtained by dividing the WDT by a half-life multiplier (HLM) value of 5.3,4 The HLM represents the number of ERH needed for the concentration in tissue to reach the tolerance level. In summary, FARAD recommends a meat WDI of 14 days for up to 0.4 mg/kg (0.18mg/lb) per os. These calculations assume that the kinetics of ivermectin are linear. The milk WDI would be 6 days based on a study by Scott et al,8 that demonstrated that at 6 days, goats' milk was clear of the drug after an oral dose of 0.2 mg/kg. Based on this information, oral administration up to 0.4 mg/kg will require a milk WDI of at least 8 days in dairy goats.
Subcutaneous route in goats-Ivermectin was detected up to 25 days in milk from lactating goats given 0.2 mg/kg SC.2 There were no differences between plasma and milk pharmacokinetic variables, and the milk
Topical route in goats-Topical application of ivemectin (0.5 mg/kg [0.23 mg/lb]) to dairy goats resulted in about 0.5 ng/ml in milk at 6 days.8 Because milk residues were not detected at 7 days, this time can be used as a milk WDI for goats given ivermectin topically. Tissues were not assayed, but plasma concentrations were less than 1.0 ng/ml at 6 days, supporting the milk-plasma relationship described.