Category: Administration

The veterinary pharmacokinetics and safety protocols for ivermectin administration in canines require strict adherence to weight-based dosing and genetic screening. Ivermectin is a macrocyclic lactone used primarily for heartworm prevention (Dirofilaria immitis) at microgram doses, but its use at higher milligram doses for treating mange (Demodex or Sarcoptes) carries significant risk of neurotoxicity in specific breeds.

The Veterinary Pharmacokinetics & MDR1 Genetic Toxicology hub analyzes the safe use of antiparasitics. Core attributes include the mechanism of action (binding to glutamate-gated chloride channels in parasites), the calculation of therapeutic indices, and the critical importance of the ABCB1 (formerly MDR1) gene mutation. The clinical value lies in preventing ivermectin toxicosis, a potentially fatal neurological condition.

The Blood-Brain Barrier & ABCB1 (MDR1) Mutation

We examine how the ABCB1 gene codes for P-glycoprotein, a transport pump that normally pushes drugs like ivermectin out of the central nervous system, maintaining the blood-brain barrier. Our pharmacological guides focus on breeds predisposed to the mutation (Collies, Australian Shepherds, Longhaired Whippets) and the symptoms of toxicity (ataxia, hypersalivation, mydriasis, coma). Understanding the pharmacogenetics ensures safe administration and prevents iatrogenic harm.

FAQ: Veterinary Pharmacology

Why are Collies sensitive to ivermectin? Many herding breeds carry a mutation in the ABCB1 (MDR1) gene. This gene produces P-glycoprotein, which acts as a bouncer at the blood-brain barrier, pumping out neurotoxic drugs. Dogs with the mutation lack this functional pump, allowing ivermectin to cross into the brain, bind to mammalian GABA receptors, and cause severe neurological suppression.
Is the heartworm prevention dose safe for dogs with the MDR1 mutation? Yes. The dose of ivermectin used for monthly heartworm prevention (typically 6 micrograms per kilogram of body weight) is so low that it is considered safe even for dogs with the MDR1 mutation. Toxicity in mutant dogs typically occurs at doses used to treat mange (300-600 micrograms per kilogram).

Genetics: Breed Specific Risks.