Methimazole Gel

Methimazole Gel
Usage
Methimazole gel is a compounded transdermal formulation of an antithyroid medication used to manage hyperthyroidism. It is most commonly used in veterinary medicine (especially cats) when oral administration is difficult or not tolerated.
It may be prescribed for:
• Feline hyperthyroidism
• Situations where oral methimazole is not suitable
• Other practitioner-directed uses requiring transdermal antithyroid therapy
The gel is typically applied to areas such as the inner ear (pinna) in animals for systemic absorption.

Dosage
Dosage should be determined by the prescribing veterinarian or healthcare professional based on the patient’s condition and response.
Typical dosing considerations include:
• Apply a measured amount once or twice daily, or as directed
• Applied to clean, hairless skin (commonly the inner ear in cats)
• Alternate application sites to reduce irritation
• Wear gloves during application to avoid accidental exposure
• Wash hands after application (if gloves are not used)
Regular monitoring of thyroid levels is required to guide dosing.

Mechanisms of Action
Methimazole is an antithyroid agent that reduces thyroid hormone production.
Its mechanisms include:
Inhibition of thyroid hormone synthesis
Methimazole inhibits the enzyme thyroid peroxidase, which is involved in the iodination of tyrosine residues.
Reduction of T3 and T4 production
This decreases the synthesis of thyroxine (T4) and triiodothyronine (T3).
Control of hyperthyroidism
By lowering thyroid hormone levels, methimazole helps reduce symptoms such as weight loss, hyperactivity, and tachycardia.
With transdermal use, methimazole is absorbed through the skin and exerts systemic effects.

Contraindications
Methimazole gel should not be used in:
• Patients with hypersensitivity to methimazole or related compounds
• Pregnant animals, unless benefits outweigh risks
• Patients with severe liver disease or blood disorders (unless under close supervision)

Precautions
Methimazole gel should be used with caution in:
• Patients with hepatic impairment
• Patients with blood dyscrasias (e.g., leukopenia)
• Situations where systemic absorption may vary
Additional considerations include:
• Regular monitoring of thyroid function, liver enzymes, and blood counts is recommended
• Possible side effects include:
• Skin irritation at application site
• Gastrointestinal upset
• Lethargy
• Caregivers should avoid direct skin contact with the medication
• Use gloves to minimise human exposure
Patients/owners should seek veterinary advice if they notice worsening symptoms, lethargy, or signs of adverse reactions.

Storage
• Store below 25°C unless otherwise directed
• Keep the container tightly closed when not in use
• Protect from heat, moisture, and direct light
• Do not freeze unless specifically instructed
• Store safely to avoid accidental exposure to humans or other animals
Follow the specific storage instructions provided on the dispensing label.