This content was preserved from the original amberfoundation.org page. The Amber Foundation was Dennis’ attempt to share information on feral cat care and especially treating feline mange.
WARNING For Ivermectin Users
Ivermectin is a poison. That’s how it cures mange and other parasitic diseases: it kills the parasites.
The trick is using enough poison to kill the parasites, but leave the pet unharmed. This means that Ivermectin dosage must be precisely calculated and carefully measured.
If you are considering treating your cat with Ivermectin, please consider as an alternative the best mange treatment.
Signs Of Ivermectin Poisoning
The clinical signs of Ivermectin poisoning are:
- excessive dilatation of the pupil of the eye (mydriasis)
- lethargy
- stupor
- coma
- tremors
- loss of coordination of the muscles, especially of the extremities (ataxia)
- vomiting (emesis)
- drooling
- death
Ivermectin acts on insects by potentiation of GABA-ergic neural and neuromuscular transmission but since mammals have only central GABA-ergic synapses which are to a large extent protected by the blood-brain barrier they are relatively resistant to ivermectin. Some penetration of the blood-brain barrier does occur at relatively high doses, with brain levels peaking between two and five hours after administration. Symptoms seen in a range of mammalian species are CNS depression, and consequent ataxia, as might be expected from potentiation of inhibitory GABA-ergic synapses (Hayes & Laws, 1991).
Less Worrisome Things
At recommended doses, ivermectin does not readily penetrate the CNS of mammals, where GABA functions as a neurotransmitter. The principal peripheral neurotransmitter, acetylcholine, is unaffected by ivermectin (MSD, 1988).
When Ivermectin is used properly, there may still be some unpleasant side-effects caused by the sudden death of massive numbers of parasites: rash, itchiness.
It is thought there are no long term effects from mild overdoses.
Dangers Due To Overdose
Of the various signs of Ivermectin poisoning, not all are life-threatening. So where does the danger come from?
Respiratory Depression
According to studies on Rats and Dogs quoted in PIM 292, high doses “cause death due to respiratory depression.”
Anorexia and Dehydration
According to studies on Dogs quoted in PIM 292, continued low doses of Ivermectin caused anorexia and dehydration.
Reproductive Problems
According to PIM 292, there is no evidence of increased birth defects in humans or mares subject to normal therapeutic Ivermectin treatment. But
Ivermectin is teratogenic in rats, rabbit and mice at or near materno-toxic dose levels. The abnormalities are limited mainly to cleft palate. Mice are the most sensitive species to the effect of ivermectin with maternotoxicity at a dose of 0.2 mg/kg/day (MSD, 1988).
Treating Overdose
Treatment is symptomatic and supportive in cases of overdose. Adverse effects are transient, but analgesics and antihistamines may be required. Since ivermectin is believed to enhance GABA activity in animals, it is probably wise to avoid drugs that enhance GABA activity (benzodiazepines, barbiturates, valproate, valproic acid) in patients with potentially toxic ivermectin exposure (MSD, 1988).
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Supportive measures are indicated in case of life- threatening poisoning (which is rare). Analgesics and antihistamines are indicated for the treatment of adverse effects.
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In case of ingestion of significant amounts of ivermectin, induce emesis using syrup of ipecac. Gastric lavage may be undertaken.
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The efficacy of activated charcoal in gut decontamination following ingestion of ivermectin has not been documented and warrants investigation.
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Some authors have suggested the use of picrotoxin and physostigmine as antidotal therapies. However, animal studies with these agents employing these agents as antidotes in ivermectin toxicity have been unsatisfactory and are not recommended (Iliff-Sizemore et al., 1990).
Tabulated Findings
I did a lot of research on the web. This section summarizes my findings.
WARNING: If you actually intend to use any of this information, check it with the original source. Watch out for outdated information and typographical errors!
Animals Sensitive To Ivermectin
- Certain dogs: Collies, Old English Sheepdogs, and related breeds or crosses. [See: Bimectin Datasheet.] This includes Shetland Sheepdogs, Australian Shepherds, Border Collies, and Shelties. Use caution with any herding breed. For mixed breed dogs of unknown lineage, the ivermectin rule is “White feet, don’t treat!” [See: veterinarypartner.com.]”Depression, tremors, mydriasis, ataxia, coma and death have been seen in Collie dogs at .100 mg/kg orally and greater, but not at the recommended dose of the commercial product (.006 mg/kg).” – PIM 292.
- Turtles/tortoises. See: Bimectin Datasheet.
- Neonatal pigs (Piglets < 5 days). see: Bimectin Datasheet.
- Aquatic life. Ivermectin is very toxic to fish and other water-borne organisms. Properly dispose of leftover material!
Animals Commonly Treated With Ivermectin
- Cattle. See: Bimectin Datasheet.
- Reindeer. See: Bimectin Datasheet.
- Pigs. See: Bimectin Datasheet.
Drug Interactions
- “Preliminary in vivo studies demonstrate that ivermectin can enhance some of the pharmacological actions of diazepam (MSD, 1988).” See: PIM 292.
Therapeutic Ivermectin Dosage For Various Animals
Dosage in mg ivermectin per kg bodyweight.
| animal | dose | route | use | notes | reference |
|---|---|---|---|---|---|
| Cattle | 0.2 mg/kg | S.C. | G.I. roundworms, lungworms, warbles, mange mites, lice | Bimectin Datasheet | |
| Reindeer | 0.2 mg/kg | S.C. | larval stages of Hypoderma Tarandi | Bimectin Datasheet | |
| Pigs | 0.3 mg/kg | S.C. | G.I. roundworms, lungworms, mange mites, lice | Bimectin Datasheet | |
| Human, adult | .150 to .200 mg/kg | oral? | onchocerciasis and other parasitic infections | PIM 292 | |
| Human, children | .150 mg/kg | oral? | onchocerciasis and other parasitic infections | not for children weighing less than 15 kg | PIM 292 |
| ANIMAL | DOSE | ROUTE | USE | NOTES | REF |
Fatal Ivermectin Dosage For Various Animals
Dosage in mg ivermectin per kg bodyweight.
| animal | gender | LD50 dose | route | reference |
|---|---|---|---|---|
| Mouse | female | 24.6-41.6 mg/kg | oral | PIM 292 |
| Mouse | male | 11.6 mg/kg | oral | PIM 292 |
| Rat young adult | female | 44.3-52.8 mg/kg | oral | PIM 292 |
| Rat young adult | male | 42.8-52.8 mg/kg | oral | PIM 292 |
| Rat infant | male & female | 2.3 mg/kg | oral | PIM 292 |
| Rat | 660 mg/kg | dermal | PIM 292 | |
| ANIMAL | GENDER | DOSE | ROUTE | REF |
Pharmacokinetic Properties
| animal | route | maximum plasma concentration | biological half-life | reference |
|---|---|---|---|---|
| Pigs | S.C.? | 3.5 days | 5.5 days | Bimectin Datasheet |
| Human | Oral | 10-12 hours | PIM 292 | |
| Rat | I.V. | 1 day | PIM 292 | |
| Cattle | Oral | 2.7 days | PIM 292 | |
| Cattle | S.C. | 2.9 days | PIM 292 | |
| Cattle | S.C.? | 5.5 days | 6 days | Bimectin Datasheet |
| Cattle | Topical | 15.9 days | PIM 292 | |
| ANIMAL | ROUTE | MAX-PLASMA | HALF-LIFE | REF |