Small Animal Dermatology, 3rd edition

CHAPTER 19 DEMODICOSIS (CANINE AND FELINE) 303

Risk of neurotoxicosis and propylene glycol sensitivity

Ivermectin use is discouraged at this time.

Drug Toxicities

 The combined use of medications (amitraz and ivermectin) is strongly discouraged

and should be avoided due to potential toxicity.

 Amitraz:
Most common side effects: somnolence, lethargy, depression, anorexia seen in

30% of patients for 12–36 hours after treatment

Other side effects: vomiting, diarrhea, pruritus, polyuria, mydriasis, bradycardia,

hypoventilation, hypotension, hypothermia, ataxia, ileus, bloat, hyperglycemia,

convulsions, death

The incidence and severity of side effects do not appear to be proportional to the

dose or frequency of use

Humans may develop dermatitis, headaches, and respiratory difficulty after

exposure; apply in a well-ventilated room

Use of alpha 2-adrenergic antagonists can reverse signs of toxicosis. Atipamezole

(Antisedan) (0.05 mg/kg intramuscularly) can reverse adverse signs in 10 min-

utes; may repeat every 4–8 hours

Yohimbine (0.11 mg/kg intravenous) administer slowly; may repeat every

4–8 hours

Avoid antidepressants and MAOIs, such as selegiline, in dogs receiving amitraz

Shampoo with mild soap to remove the topical product (dip or spot-on).

 Ivermectin and milbemycin:
Breed: related toxicities (see above)
Signs of toxicity: salivation, vomiting, mydriasis, confusion, ataxia, hypersensi-

tivity to sound, weakness, recumbency, coma, and death

Ivermectin should not be given in conjunction with P-glycoprotein inhibitors:

antidepressants (fluoxetine, paroxetine, St John’s wort), antimicrobials (ery-

thromycin, itraconazole, ketoconazole), opioids (methadone, pentazocine),

cardiac drugs (amiodarone, carvedilol, nicardipine, quinidine, verapamil),

immunosuppressants (cyclosporine, tacrolimus), miscellaneous (bromocrip-

tine, chlorpromazine, grapefruit juice, tamoxifen, spinosad)

Therapy for toxicosis: supportive and symptomatic care; atropine or glycopyrro-

late as needed to treat bradycardia; avoid other drugs that stimulate the GABA

receptors (benzodiazepam tranquilizers).

COMMENTS

Expected Course and Prognosis

 Prognosis (dogs): depends heavily on genetic, immunologic, and underlying diseases.

 Localized: most cases (90%) resolve spontaneously with no treatment;<10% progress

to the generalized form.