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The following Overview, *** IVERMECTIN AND RELATED AGENTS ***, is relevant for this HSDB record chemical. |
0.2.1 SUMMARY OF EXPOSURE
0.2.1.1 ACUTE EXPOSURE
A) USES: Avermectins are macrocyclic lactones used for
control of nematode and arthropod parasites. Ivermectin
0.5% topical lotion is used for the topical treatment
of head lice infestations. Oral ivermectin is indicated
for the treatment of nondisseminated strongyloidiasis
of the intestinal tract and Onchocerciasis (river
blindness), due to the non-adult stage of nematode
parasite Onchocerca volvulus. Abamectin, doramectin,
and eprinomectin are agricultural miticides and
insecticides. Selamectin is a topical parasiticide.
Moxidectin is a parasiticide given to animals (ie,
dogs, cats, livestock, horses) for the prevention,
treatment and/or control of parasites, such as
heartworms. Moxidectin is from the milbemycin class,
and is a semisynthetic derivative of nemadectin.
B) PHARMACOLOGY: The macrocyclic lactone (macrolide)
antimicrobial class contains 2 closely related chemical
groups, avermectins and milbemycins. These 2 chemical
groups have a large complex macrocyclic backbone and
have been produced by fermentation of soil dwelling
fungal organisms (genus Streptomyces). Ivermectin is a
semisynthetic antiparasitic drug and a member of the
avermectin class. It binds selectively and with high
affinity to glutamate-gated chloride ion channels in
invertebrate muscle and nerve cells of the
microfilaria. This binding causes an increase in the
permeability of the cell membrane to chloride ions and
results in hyperpolarization of the cell, leading to
paralysis and death of the parasite. Ivermectin also is
believed to act as an agonist of the neurotransmitter
gamma-aminobutyric acid (GABA), thereby disrupting
GABA-mediated central nervous system (CNS)
neurosynaptic transmission.
C) EPIDEMIOLOGY: Overdose is rare.
D) WITH THERAPEUTIC USE
1) Ivermectin is generally well-tolerated following
therapeutic use. Pruritus and tachycardia have been
reported.
E) WITH POISONING/EXPOSURE
1) MILD TO MODERATE TOXICITY: Rash, urticaria, pruritus,
edema, headache, dizziness, somnolence, asthenia,
nausea, vomiting, abdominal pain, diarrhea, and mild
tachycardia have been reported.
2) SEVERE TOXICITY: In severe overdose, seizures, coma,
aspiration pneumonia, metabolic acidosis, respiratory
failure, and hypotension may develop.
3) DRUG INTERACTION: Ivermectin is thought to potentiate
GABA activity. Other drugs, such as barbiturates,
benzodiazepines and valproic acid, which also enhance
GABA activity, may increase its toxicity.
4) ANIMAL STUDIES: In animals, high dose ivermectin may
produce a CNS toxicosis consisting of tremors, ataxia,
weakness, incoordination, recumbency, dehydration and
coma.
0.2.3 VITAL SIGNS
0.2.3.1 ACUTE EXPOSURE
A) WITH POISONING/EXPOSURE
1) Mild tachycardia, hypotension, fever, and hypothermia
have been reported.
0.2.4 HEENT
0.2.4.1 ACUTE EXPOSURE
A) ANIMAL STUDIES: Mydriasis has been reported during
pharmacological testing in dogs.
B) WITH THERAPEUTIC USE
1) Sore throat has been observed.
C) WITH POISONING/EXPOSURE
1) Mydriasis developed in one pupil of a child who
accidentally ingested 7 mg/kg.
2) When accidentally sprayed into the eye of an adult,
only stinging resulted.
0.2.13 HEMATOLOGIC
0.2.13.1 ACUTE EXPOSURE
A) WITH THERAPEUTIC USE
1) Prolonged prothrombin times and hematoma formation
have been reported as side effects of ivermectin
treatment.
0.2.15 MUSCULOSKELETAL
0.2.15.1 ACUTE EXPOSURE
A) WITH THERAPEUTIC USE
1) Arthralgia, synovitis, bone pain, and myalgia have
been reported.
0.2.20 REPRODUCTIVE HAZARDS
A) Ivermectin is classified as FDA pregnancy category C. In
a study of pregnant women who received ivermectin, no
adverse effects were observed. However, ivermectin has
the potential for crossing the blood-brain barrier
following high doses and causing CNS effects. In animal
studies, ivermectin has resulted in cleft palate
following doses at or near levels that are maternotoxic
in mice, rats and rabbits. Ivermectin is excreted in
breast milk at low concentrations. Breast milk
concentrations were a mean of 14 nanograms/mL following
administration of oral ivermectin to nursing mothers.
0.2.23 OTHER
0.2.23.1 ACUTE EXPOSURE
A) WITH THERAPEUTIC USE
1) Swelling and tenderness of the lymph glands has been
reported. |
0.4.2 ORAL EXPOSURE
A) MANAGEMENT OF MILD TO MODERATE TOXICITY
1) Treatment is symptomatic and supportive. Manage mild
hypotension with IV fluids.
B) MANAGEMENT OF SEVERE TOXICITY
1) Treatment is symptomatic and supportive. Treat seizures
with IV benzodiazepines; barbiturates or propofol may
be needed if seizures persist or recur. Treat severe
hypotension IV 0.9% NaCl at 10 to 20 mL/kg. Add
dopamine or norepinephrine if unresponsive to fluids.
Treat severe metabolic acidosis (pH less than 7.1) with
sodium bicarbonate 1 to 2 mEq/kg. Consider intravenous
lipid emulsion in patients with dysrhythmias,
hypotension or severe CNS toxicity secondary to
ivermectin intoxication.
C) DECONTAMINATION
1) PREHOSPITAL: Prehospital gastrointestinal
decontamination is not recommended because of the
potential for CNS depression or persistent seizures and
subsequent aspiration.
2) HOSPITAL: Consider activated charcoal if the overdose
is recent, the patient is not vomiting, and is able to
maintain airway.
D) AIRWAY MANAGEMENT
1) Ensure adequate ventilation and perform endotracheal
intubation early in patients with respiratory or CNS
depression or hemodynamic instability.
E) ANTIDOTE
1) None
F) ENHANCED ELIMINATION
1) Hemodialysis is unlikely to be of value because of the
high degree of protein binding and large volume of
distribution.
G) PATIENT DISPOSITION
1) HOME CRITERIA: A patient with an inadvertent exposure,
that remains asymptomatic can be managed at home.
2) OBSERVATION CRITERIA: Patients with a deliberate
overdose, and those who are symptomatic should be
observed with frequent monitoring of vital signs.
Patients that remain asymptomatic can be discharged.
3) ADMISSION CRITERIA: Patients should be admitted for
severe vomiting, profuse diarrhea, severe abdominal
pain, dehydration, and electrolyte abnormalities.
Patients with unstable vital signs, persistent
seizures, coma, metabolic acidosis, or respiratory
failure should also be admitted.
4) CONSULT CRITERIA: Consult a poison center or medical
toxicologist for assistance in managing patients with
severe toxicity or in whom the diagnosis is not clear.
H) PITFALLS
1) When managing a suspected overdose, the possibility of
multidrug involvement should be considered.
I) PHARMACOKINETICS
1) Ivermectin is absorbed orally, parenterally, and
dermally. Tmax: 3 to 5 hours after oral dosing. Protein
binding: approximately 93%. Vd: 46.9 L. Ivermectin and
its metabolites are most likely excreted in the bile.
Elimination half-life: oral, 10 to 18 hours (may be 1
to 4 days in various animal species).
J) DIFFERENTIAL DIAGNOSIS
1) Includes other chemicals or drugs that cause
hypotension (eg, vasodilators, beta blockers, calcium
channel blockers), metabolic acidosis (eg,
salicylates), or CNS depression (eg, toxic alcohols,
benzodiazepines, opiates/opioids, antipsychotic
medications). Diseases or exposures that produce acute
respiratory distress (eg, inhalation of acid or
alkaline mists, asthma, COPD). |
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