Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.

METHIMAZOLE

Chemistry - A thioimidazole-derivative antithyroid drug, methimazole occurs as a white to palebuff crystalline powder, having a faint characteristic odor and a melting point of 144 -147°C. It isfreely soluble (1 gram in 5 ml) in water or alcohol.

Storage, Stability, Compatibility

Methimazole tablets should be stored in well-closed, light-resistant containers at room temperature.

Pharmacology - METHIMAZOLE

Methimazole interferes with iodine incorporation into tyrosyl residues of thyroglobulin, thereby inhibiting the synthesis of thyroid hormones. It also inhibits iodinated tyrosylresidues from coupling to form iodothyronine. Methimazole has no effect on the release or activityof thyroid hormones already formed or in the general circulation.
Uses, Indications - Methimazole is considered by most clinicians to be the agent of choice whenusing drugs to treat feline hyperthyroidism. Propylthiouracil has significantly higher incidences ofadverse reactions when compared to methimazole.

Pharmacokinetics - METHIMAZOLE

Information on the pharmacokinetics of methimazole in cats is available(Trepanier, Peterson, and Aucoin 1989). These researchers reported that in normal cats, thebioavailability of the drug is highly variable (45-98%), as is the volume of distribution (0.12 - 0.84
L/kg). After oral dosing, the plasma elimination half-life ranges from 2.3 - 10.2 hours. There isusually a 1-3 week lag time between starting the drug and significant reductions in serum T4.
Methimazole apparently concentrates in thyroid tissue.
Contraindications/Precautions - Methimazole is contraindicated in patients who are hypersensitive to it. It should be used very cautiously in patients with a history of or concurrent hematologicabnormalities, liver disease or autoimmune disease.

Adverse Effects, Warnings

Approximately 15-20% of cats treated with methimazole developadverse effects. In a study of 262 cats receiving methimazole (Peterson, Kintzer, and Hurvitz 1988), the following adverse effects (% incidence) were reported: anorexia (11.1%), vomiting (10.7%), lethargy (8.8%), excoriations (2.3%), bleeding (2.3%), hepatopathy (1.5%), thrombocytopenia(2.7%), agranulocytosis (1.5%), leukopenia (4.7%), eosinophilia (11.3%), lymphocytosis (7.2%), positive ANA (21.8%), positive direct antiglobulin test (1.9%). Clinical symptoms were noted in18.3% of the cats. The gastrointestinal adverse effects generally developed within the first month oftreatment and usually resolved even with continued therapy.
High levels of methimazole cross the placenta and may induce hypothyroidism in kittens born ofqueens receiving the drug. Levels higher than those found in plasma are found in human breastmilk. It is suggested that kittens be placed on a milk replacer after receiving colostrum frommothers on methimazole.
Overdosage - Acute toxicity that may be seen with overdosage include those that are listed aboveunder Adverse Effects. Agranulocytosis, hepatopathy, and thrombocytopenias are perhaps the mostserious effects that may be seen. Treatment consists of following standard protocols in handling anoral ingestion (empty stomach if not contraindicated, administer charcoal, etc.) and to treatsymptomatically and supportively.

Drug Interactions

Apparently no significant drug interactions have been reported for this drug.
Click here add new comment/review152

Similar Drugs

leventa® 30mL
Equistrength
Acidified Cupric Sulfate
NitroTop
Surpass® (1% diclofenac sodium) Topical Anti-Inflammatory CreamFor Use in Horses
REVOLUTION® (selamectin) Topical Parasiticide For Dogs and Cats
Fish Egg Disinfectant Ovadine® (Buffered PVP Iodine) Ovadine® is a polyvinylpyrrolidone iodine (PVP-Iodine) complex designed for use as a fish egg disinfectant. Ovadine contains 10% Povidone Iodine complex that provides 1% available iodine.
AERRANE (isoflurane, USP) Inhalation Anesthetic For Use in Horses and Dogs
CORONA ORIGINAL LANOLIN-RICH OINTMENT
Spectam Water Soluble Concentrate (spectinomycin) NADA 038-661, Approved by FDA Bimeda, Inc. Division of Cross Vetpharm Group
For Dogs, cats, and small pets
CORONA UDDER BUTTER
Excel
Hex-Tra
HEX-PLUS
PREDYNE Iodine udder wash
HEX-WASH
CYDECTIN® moxidectinPour-On for Beef and Dairy CattleAntiparasitic
Acarexx® (0.01% ivermectin) Otic Suspension
LincoMed 300
TRICAINE-S Brand of Tricaine Methanesulfonate For Anesthesia and Tranquilization of Fishes and Other Cold-Blooded Animals
CARPROFEN CAPLETS
Heartworm Preventative & Intestinal Parasite Treatment
Broad Spectrum De-Wormer Chewable Tablets for Large Dogs
Hexasol TM Injection (oxytetracycline and flunixin meglumine)
ToMORROW® cephapirin benzathinecefapirina benzatinicaFOR INTRAMAMMARY INFUSION INTO THE DRY COWPARA INFUSION INTRAMAMARIA EN VACAS SECAS
Bimectin
Durvet Sulfadimethoxine Soluble Powder (sulfadimethoxine) ANADA 200-376, Approved by FDA
Oxytocin
Dexamethasone

veterinary-help.com

© 2011-2025 Veterinary Clinics, Diagnoses, Terms and Drug Handbook Online

×
Wait 20 seconds...!!!